Icom mods schematic

Modifications for the ICOM

created 28-03-2002 from www.mods.dk

(AH-4)
(AT-160)
(AT-500)
(AT-500)
(I290)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-02)
(IC-03)

Icom, AH-4, AH-3 ( automatic antenna tuner ) connection to any radio. English language
Using the AT-160 with the IC-706MKII English language
AT-500 Automatic Antenna Tuner Modification English language
ICOM AT-500 Tuner Hint English language
Icom I290 scan modification English language
Band expansion modification for IC-02AT English language
Audio modification for IC-02 AND IC-04 English language
IC-02A Modified PLL rigs English language
Low audio speaker mike on IC2A, 3A, 4A OR 02AT English language
ICOM 02/03/04 & Vox Unit English language
Another band expansion mods for Icom IC-02 English language
For increased receive audio and improved response English language
To increase the memory scan and search scan speed English language
ICOM HS-10SA VOX for IC-02AT Mods English language
ICOM 02/03/04 & Vox Unit English language

(IC-04)
(IC-04)
(IC-04)
(IC-04)
(IC-04)
(IC-04)
(IC-1200)
(IC-1271)
(IC-1271)
(IC-1275)
(IC-1275)
(IC-1275)
(IC-1275)
(IC-1275)
(IC-1275)

ICOM 02/03/04 & Vox Unit English language
Out of band modification for IC-04 English language
Audio modification for IC-02 AND IC-04 English language
Low audio speaker mike on IC2A, 3A, 4A OR 02AT English language
TX delay may be excessive at low temperatures English language
IC-04E fuer 9k6 German language
Expanded RF 870 - 960 MHz for ICOM IC-1200 English language
VOX of an IC-271,471,1271 usable for FM English language
RAM Card Backup Battery Replacement Instructions English language
IC-1275 Freq. steps mod English language
Power control modification English language
Restoration of pass band tuning English language
Splitting into RX- and TX paths English language
Modification of cw pass band (BFO) English language
Disabling of SBB squelch English language

(IC-1275)
(IC-1275)
(IC-1275)
(IC-1275)
(IC-1275)
(IC-2)
(IC-2)
(IC-2)
(IC-2)
(IC-2)
(IC-2)
(IC-2000)
(IC-207)
(IC-207)
(IC-210)

Very fast AGC English language
SSB RF Gain English language
Tuning speed English language
Frequency range & CTCSS tones English language
IC 475H / 1275E mod for 9k6 (G3RUH) use English language
Modification For IC-2AT English language
Low audio speaker mike on IC2A, 3A, 4A OR 02AT English language
ICOM IC-2AT internal antenna connection problem English language
ICOM IC-2GAT ext frq for Transmit English language
IC-2AT, If transmit RF indicator notwork properly English language
Icom IC-2GXAT open RX English language
Icom IC-2000 Extended RX/TX Mod English language
Band expansion for IC-207 English language
Band Expansion for IC-207H English language
Schematic of IC-210 English language

(IC-2100)

Icom IC-2100H Extended Transmit Mod English language

(IC-2100)

Expand receiver for IC-2100H EUR version English language

(IC-211)
(IC-22)
(IC-22)
(IC-22)
(IC-22)
(IC-22)
(IC-22)
(IC-228)
(IC-229)
(IC-229)
(IC-229)
(IC-2320)
(IC-2330)
(IC-2330)
(IC-2340)

IC-211 mod English language
Icom IC22S Packet Modification English language
IC-22S mods for 5 KHz step English language
Step modification (packet radio operation) English language
Band segment modification English language
Recieve SSB and CW on IC-22S English language
Modifying the IC22A for 9600 baud operation English language
IC-228 mods English language
IC-229H, and AM aviation band modification English language
IC-229H & 9600 bauds (Anglais) English language
IC-229H Fix CPU/Display board English language
Extended RX/TX English language
IC2330A expanded range English language
IC-2330A expanded range (another way) English language
IC2340H att modification English language

(IC-2340)
(IC-2340)
(IC-2350)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-24)
(IC-240)
(IC-2400)
(IC-2400)

Some mods for the IC-2340H English language
IC-2340 mods English language
IC-2350 expand RX/TX and Crossband rep English language
Frequency expansion for IC24 English language
Cross-band repeater operation IC-2 English language
Out of band modification of the ICOM IC-24AT English language
IC-24AT ext frquency English language
IC-24AT Keyboard command summary English language
IC-24AT sensitivity English language
IC-24AT enabling the burst-tone English language
IC-24 auf 9600 Baud German language
Tip to to function bottom for IC-24 English language
12,5 Khz mods for IC-240 English language
ICOM 2400A mini repeater function English language
IC-2400 144/430 9K6 mod Other language

(IC-2410)
(IC-2410)
(IC-2410)
(IC-2410)
(IC-2410)
(IC-2410)
(IC-2500)
(IC-2500)
(IC-251)
(IC-251)
(IC-251)
(IC-260)
(IC-27)
(IC-27)
(IC-2700)

Expansion of receive range English language
800 MHz antenna input English language
Cross-band repeat English language
IC-2410 Dual Band External & Mike Remote Codes English language
IC-2410 Modification area as follows. New and old version English language
IC-2410 TX modification English language
Run 9k6 with an Icom IC-2500 (70cm/23cm TRX) English language
Umbau des ICOM IC-2500E auf 9600 Baud German language
Modifikcation af IC-251 for 9600 baud English language
Modifications for the ICOM IC-251 English language
IC-251 Receive-repair English language
IC-260E auf 9600BD German language
IC-27 mic-connector mods English language
ICOM IC-27H 2M transceiver for use with the 9k6 English language
IC-2700 RX/TX expansion English language

(IC-2700)
(IC-2700)
(IC-271)
(IC-271)

IC-2700 Cross Band Repeater English language
Enabling ICOM 2700H remote operation English language
PSK Transmit Audio Modification for ICOM IC275 & IC271 English language
VOX of an IC-271,471,1271 usable for FM English language

(IC-271)

IC-271 / 471 fuer 9k6 German language

(IC-271)
(IC-271)
(IC-2710)
(IC-2710)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)

IC-271 sounds raspy in SSB/CW English language
RAM Card Backup Battery Replacement Instructions English language
Some modification for IC-2710 English language
Crossband Repeater Operation for the IC-2710 English language
PSK Transmit Audio Modification for ICOM IC275 & IC271 English language
IC-275 Freq. steps mod. English language
Band Expand for ICOM IC-275E/H and IC-275A/H English language
IC amplifier oscillates English language
Prevent PLL unlock at high ambient temperature English language
Improve voice synthesizer and side tone audio English language
Prevention of PLL unlock at 174 MHz English language
Improve the stability of the center meter English language
Noise coming from speaker during transmit with audio turned up English language
Eliminate possible spurious emission when thermal switch has turned on during TX English language
Frequency range & CTCSS tones English language

(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-275)
(IC-28)
(IC-28)
(IC-2800)
(IC-2800)
(IC-2800)
(IC-2800)
(IC-2800)

Power control modification English language
Restoration of pass band tuning English language
Modification of cw pass band (BFO) English language
Disabling of SBB squelch English language
Very fast AGC English language
SSB RF Gain English language
Tuning speed English language
Splitting into RX- and TX paths English language
ICOM IC-28A AND IC-28H ext frq English language
The long, noisy squelch-tail of the Icom IC-28 English language
Icom IC-2800h Extended RX Mod English language
Icom IC-2800 Extended RX/TX Mod English language
Icom IC-2800 Extended RX/TX Mod, Australian model English language
IC-2800/HM98 tx-audio mod English language
sensitivity ICOM IC-2800H English language

(IC-2800)
(IC-2800)
(IC-2800)
(IC-2800)
(IC-2800)
(IC-281)
(IC-281)
(IC-281)
(IC-2AT)
(IC-2AT)
(IC-2GAT)
(IC-2GAT)
(IC-2GAT)
(IC-2GAT)
(IC-2GXAT)

IC-2800H cross band mode operation English language
DTMF options card English language
Screen saver Turn OFF option for IC-2800 English language
Cross Band Repeat for IC-2800 English language
Enable crossband function for IC-2800 English language
Crossband repeat English language
Extended Receive for IC-281 English language
Extended Transmit for IC-281 English language
Coverage IC-2AT 140-150 MHz English language
Operation and L3 ADJUSTMENT English language
Out-of-band transmit mod for IC-2GAT handheld 2M transceiver English language
Step mods for IC-2GAT English language
IC-2GAT to packet English language
ICOM IC-A20 alkaline headset-adapter lost-in-the-soup English language
The ICOM 2GXAT HARDWARE MOD English language

(IC-2GXAT)
(IC-2IA)
(IC-2IA)
(IC-2IA)

Software mod, to open IC-2GXAT English language
IC-2Ia mic mods English language
IC-2IA lousey xmit audio fix English language
IC-2IA mod. English language

(IC-2SAT)

IC-2SAT out-of-band transmit mod English language

(IC-2SAT)
(IC-2SAT)
(IC-2SAT)
(IC-2SAT)
(IC-2SE)
(IC-2SE)
(IC-2SE)
(IC-2SRA)
(IC-3)
(IC-32)
(IC-32)
(IC-32)
(IC-32)
(IC-32)
(IC-32)

Icom IC-2SAT enhancements English language
IC-2SA/E Frequency range expantion English language
Icom IC-2SAT unpublished Specificatons English language
Software coverage mods, IC-2SAT English language
Additional functions of the ICOM IC-2SE English language
Extended Icom IC-2SE functions English language
Extending the Rx. coverage of the IC-2SE and IC-4SE English language
Extended Receive, Extended TX (136-174 MHZ) English language
Low audio speaker mike on IC2A, 3A, 4A OR 02AT English language
Out of band mod for the IC-32AT English language
IC-32E auf 9k6 German language
IC-32AT Elimination of possible faint pulse noise English language
Undocumented features of the ICOM IC-32AT English language
Cross-band repeater (Icom) English language
Receive coverage for VHF & UHF and enable keyboard entry English language

(IC-3200)
(IC-3200)
(IC-3200)
(IC-3200)
(IC-3200)
(IC-3210)
(IC-3210)
(IC-3220)
(IC-3220)
(IC-3220)
(IC-3230)
(IC-3230)
(IC-37)
(IC-37)
(IC-3J)

Fix for IC-3200A used on packet English language
IC-3200A TX to RX delay fix English language
IC-3200A ext frq 430-440 MHz English language
How To Expand The Coverage Of The Icom 3200A Mobile Radio. English language
Frequency Extention RX / TX for ICOM 3200 E English language
IC-3210 prevent signals on TX when the PA modul English language
9K6 with IC-3210 A/E English language
How to iface Ic-3220 & G3RUH English language
ICOM IC-3220A/H Frequency expansion English language
ICOM IC-3220A/H mini repeater function English language
ICOM IC-3230 Mods for 9k6 English language
IC-3230 repeater function English language
some audio mods for IC-37 English language
Now, here is the official Condor Connection IC-37 modification sheet English language
Expanded RX for ICOM IC-3J English language

(IC-4)
(IC-4)
(IC-4)
(IC-40)
(IC-45)
(IC-45)
(IC-451)
(IC-471)
(IC-471)
(IC-471)
(IC-475)
(IC-475)
(IC-475)
(IC-475)
(IC-475)

Low audio speaker mike on IC2A, 3A, 4A OR 02AT English language
IC-4E Umbau auf 9600Bd German language
IC-4GAT, fix the +5 V source crystal X-3 English language
Cloning software for IC-40S English language
IC-45A to IC--45E English language
Convertinga IC-45A to IC-45E English language
IC-451 aus 9600 German language
VOX of an IC-271,471,1271 usable for FM English language
9600 baud mod for IC-471 English language
RAM Card Backup Battery Replacement Instructions English language
IC 475H mod for 9k6 (G3RUH) use English language
Prevent a decrease in RF power output in high ambient temperatures English language
IC-475 Freq. steps mod English language
Power control modification English language
Restoration of pass band tuning English language

(IC-475)
(IC-475)
(IC-475)
(IC-475)

Splitting into RX- and TX paths English language
Modification of cw pass band (BFO) English language
Disabling of SBB squelch English language
Very fast AGC English language

(IC-475)

SSB RF Gain English language

(IC-475)
(IC-475)
(IC-475)
(IC-490)
(IC-490)
(IC-490)
(IC-4SAT)
(IC-4SE)
(IC-551)
(IC-551)
(IC-551)
(IC-551)
(IC-551)
(IC-575)
(IC-575)

Tuning speed English language
Frequency range & CTCSS tones English language
Umbau des IC475E/H zum betrieb mit G3RUH-Modem (9600 Baud) German language
Modifikation af IC-490 for 9K6 English language
IC-490A 10MHz up modification English language
Anschluss eines G3RUH Modems und AFSK-Modem an IC-490E German language
ICOM IC-4SAT extended transmit mod English language
Extending the Rx. coverage of the IC-2SE and IC-4SE English language
Modification af the ScanRate and ScanSpeed for IC551D English language
IC-551D to rx down to 47.000 MHz English language
IC-551/551D Frequency Alignment English language
IC-551/551D EX-107 VOX UNIT -- Installation English language
IC-551/551D EX-108 P.B. TUNE UNIT -- Installation English language
IC-575 Freq. steps mod English language
Power control modification English language

(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-575)
(IC-701)
(IC-701)
(IC-706)
(IC-706)
(IC-706)

Restoration of pass band tuning English language
Splitting into RX- and TX paths English language
Modification of cw pass band (BFO) English language
Disabling of SBB squelch English language
Very fast AGC English language
SSB RF Gain English language
Tuning speed English language
Frequency range & CTCSS tones English language
General Coverage TX Modification English language
Pass band Tuning Modification English language
Extended frequency converage on the ICOM IC-701 HF Transceiver English language
Computer control of ICOM 701 via accessory connecter English language
Info/mods for IC-706 English language
IC-706 Expanded frequency English language
IC706 - spare 0.3A English language

(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)
(IC-706)

MARS/CAP Modification for ICOM IC-706 English language
Icom IC-706 Review English language
Enables out-of-band transmit for 1.6 MHz to 54 MHz English language
More semsitive transmit for 2 meter English language
IC-706 60 MHz to 200 MHz bandpass filter English language
Icom IC-706 Extended RX mod English language
Some tips. German language
IC-706, MKII, MKIIG xmit mods - tip English language
IC-706 10 watt tune modification/An Icom IC706 Tune Trigger English language
"Halbautomatik" für manuelle Tuner am ICOM IC-706 German language
FM Transmit Fix English language
IC-706 Microphone Audio Response Improvement English language
Improved VHF recieve mod (see also yellow wire mod) English language
To expand the band on the VHF portion English language
Adding an extra RX-only port in the Icom IC706 English language

(IC-706mkii)
(IC-706mkii)
(IC-706mkii)
(IC-706mkii)

ICOM 706 MKII Extended transmit mod English language
Special on IC706mkII English language
TX range expansion for IC-706MKIIG English language
Expand only mod for the IC-706MkII English language

(IC-706mkii)

mods IC706 MKIIG por EA1DOU (ver. Española) Other language

(IC-706MKII)
(IC-706MKII)
(IC-707)
(IC-718)
(IC-718)
(IC-720)
(IC-720)
(IC-720)
(IC-725)
(IC-725)
(IC-728)
(IC-729)
(IC-729)
(IC-730)
(IC-735)

Modifikation IC-706MKIIG für 9k6 PR und Pactor German language
IC-706MKIIG mod English language
Receive and Transmit Expansion for ICOM IC-707 English language
IC-718 TX 1.8 - 30 MHz English language
Modify IC-718#04 to IC-718#03 English language
ICOM IC-720 extended xmit English language
Modifying IC-720A to get rid of rotary relay English language
Amtor mods FOR IC-720A English language
ICOM IC-725 MARS modifications English language
ICOM IC-725a post 1998 Version. English language
Modification Icom IC-728: General coverage TX English language
Using two Icom rigs in transceive English language
Modification Icom IC-729: General coverage TX English language
Preventative Maintenance for the ICOM IC-730 English language
Xmit Mods for IC-735 English language

(IC-735)
(IC-735)
(IC-735)
(IC-736)
(IC-736)
(IC-737)
(IC-737)
(IC-738)
(IC-740)
(IC-745)
(IC-745)
(IC-745)
(IC-746)
(IC-746)
(IC-746)

TX Mod For ICOM 735 English language
IC-735 Remote Working English language
ICOM Radio/RS232 interface which meets RS232 specifications English language
Speed-up the ALC for IC-736 English language
Icom IC-736 DDS/VCO Bug/Fix English language
Icom IC-737 general coverange in transmission English language
CW Filter Switching Modification for the Icom 737 English language
Extended TX modification for Icom IC-738 English language
Display/distortion problems ICOM IC-740 HF rig English language
IC-745 - PROBLEM: Tuning counts slowly down English language
ICOM IC-745 Unlocked English language
RAM Card Backup Battery Replacement Instructions English language
IC-746 out of range TX/RX English language
IC-746 Modification English language
Extended RX/TX for IC-746 English language

(IC-746)
(IC-746)
(IC-746)
(IC-746)
(IC-746)
(ic-746pro)
(IC-751)
(IC-751)
(IC-751)
(IC-751)
(IC-751)
(IC-751)
(IC-751)
(IC-751)
(IC-756)

Separating the Tx and Rx lines English language
Power mod for the IC-746 English language
Solutions for chip blowing with mPC English language
Monitor Audio Output Too Low English language
Schematic for ICOM CI-V Option English language
TX modification for IC-746PRO (version #02 USA) English language
Allow CW Xmit & USB recieve split mode for IC-751 English language
IC-751 to 37 MHz English language
IC-751 Bad Cap Problems English language
General coverage mod for the ICOM IC-751A English language
IC-751 Switch Matrix English language
How to replace the lithium battery in your ICOM radio English language
RAM Card Backup Battery Replacement Instructions English language
ICOM IC-751 Dual RAM back-up Battery Modification English language
IC-756 Expand TX Frequency English language

(IC-756)
(IC-756)
(IC-756)
(IC-756)

Spectrum Scope Adjustments English language
ACC1 Audio Output Increase English language
General Coverage H.F. TX Mod (1.6 - 30.0MHz) English language
IC-756 wide band modulation English language

(IC-756pro)

Expand tx-freqeuncy for the IC756-PRO English language

(IC-756PRO)
(IC-756pro2)
(IC-756PRO2)
(IC-761)
(IC-761)
(IC-761)
(IC-765)
(IC-765)
(IC-765)
(IC-765)
(IC-765)
(IC-765)
(IC-775)
(IC-775)
(IC-775)

ICOM IC-756PRO CW Filter Shape Selection English language
IC-756PRO2 TX mods 100 Khz - 60 MHz English language
TX expand on IC 756PROII #23 EU models English language
Wider SSB band on the IC-761 English language
IC-761 activate tuner when in general coverage mod English language
IC-761 Out of band English language
Icom IC-765 improved monitor volume English language
Icom IC-765 Passband tuning mod English language
Mod to prevent ant sw unit failure English language
Adjustment the mortrs control unit English language
IC-765 Extended TX Mod English language
Replace 455 SSB filter w fl 44a very nice selectivity. English language
New product information IC-775DSP English language
IC-775DSP Out of Band Information English language
Increase the sensitivity on MW-band 0.5-1.6MHz on IC-775 and IC-775DSP English language

(IC-781)
(IC-781)
(IC-781)
(IC-781)
(IC-820)
(IC-820)
(IC-820)
(IC-820)
(IC-820)
(IC-821)
(IC-821)
(IC-821)
(IC-821)
(IC-900)
(IC-900)

IC-781 General coverage transmit mod English language
781 ALC Circuit problem English language
Reduce the internal heat by the speaker English language
Icom IC-781 filter modification English language
IC-820 Test results G3RUH English language
1750Hz on IC-820, modif English language
ICOM IC-820H extended receive/transmit modification English language
ICOM IC-820H cross band repeat modification English language
IC-820H display board English language
IC-821H mods for extended TX/RX coverage: English language
ICOM IC-821H - Frequenzerweiterung: German language
ICOM IC-821H X-Band mod English language
Icom IC-821H mods English language
ICOM IC-900 Out of Band Modifications English language
IC-900 Memory Expansion Modification (Preliminary Rev II) English language

(IC-901)
(IC-901)
(IC-901)
(IC-910)
(IC-910)
(IC-970)
(IC-DELTA1)
(IC-DELTA1)
(IC-F3/4)
(IC-M100)
(IC-M11)
(IC-M125)
(IC-M56)
(IC-M58)
(IC-M58)

IC-901A Frequency Ranges English language
Memory and microprocessor reset English language
Crossband repeat English language
Expanded functions for the IC-910H (All versions) English language
IC-910H mods English language
IC-970 with 9600 Baud English language
Band expansion modification for IC-Delta1A English language
IC-Delta 1E repeater mode English language
Icom F3/4 extended RX & TX English language
Icom IC-M56, M58, M59, M100 - M125 Additional frq. range English language
Icom IC-M11 Additional frequencies and range English language
Icom IC-M56, M58, M59, M100 - M125 Additional frq. range English language
Icom IC-M56, M58, M59, M100 - M125 Additional frq. range English language
IC-M58 cloning program English language
Icom IC-M56, M58, M59, M100 - M125 Additional frq. range English language

(IC-M59)
(IC-M700)
(IC-M710)
(IC-MU2)

Icom IC-M56, M58, M59, M100 - M125 Additional frq. range English language
ICOM M-700 Marine Transceiver English language
Cloning program for IC-M710 English language
IC-MU2 Ext Band mods English language

(IC-P2AT)

ICOM P2AT keyboard mods English language

(IC-P2ET)
(IC-P3AT)
(IC-PCR1000)
(IC-PCR1000)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-Q7)
(IC-R10)
(IC-R10)
(IC-R10)

Sensitivity for the Icom IC-P2ET English language
RX and TX modifications for ICOM P3AT English language
Icom IC-PCR1000 frequency modification English language
ICOM PCR1000 Software English language
IC-Q7 Erfahrungen German language
Extending fq-tx coverage on IC-Q7E English language
Icom Q7A mods from the factory English language
Modifying the ICOM IC-Q7A for RX/TX English language
Expand transmit from 136-174 and 400-470 for IC-Q7E. (Australian version) English language
IC-Q7 Programming utility 1.05 ( Goran Vlaski ), Wide RX 0-30MHz, Adjustment mode English language
IC-Q7A Full Transmit From 140 - 174 MHz and 400 - 470 MHz English language
9k6 with ICOM IC-Q7E German language
IC-R10 Instruction Manual QUICK REFERENCE by PY3PSI English language
ICOM R10 Receiver Modification to Provide S-Meter Output English language
IC-R10 descriminator output modification English language

(IC-R3)
(IC-R71)
(IC-R71)
(IC-RP3010)
(IC-T2)
(IC-T2)
(IC-T22)
(IC-T22)
(IC-T3H)
(IC-T7A)
(IC-T7H)
(IC-T7H)
(IC-T8)
(IC-T8)
(IC-T8)

IC-R3 to receive SSB from DC to 2.450GHz including the AO-40 satellite English language
RAM Card Backup Battery Replacement Instructions English language
RAM board programming interface & R71A modification English language
IC-RP3010 disable the CTCSS English language
Expand TX/RX frequency English language
IC-T2H Receive 100-200 MHz English language
To expand receive from 136-174MHz FM to 136-174/270-410MHz FM: English language
Extended transmit for IC-T22 English language
Extended RX/TX English language
Icom IC-T7A Mods English language
Expand frequncy English language
Disassembly instructions for IC-T7H English language
IC-T8 AM/FM/Wfm function English language
Software mods to open the RX-band English language
Problem with the battery pack English language

(IC-T8)
(IC-T8)
(IC-T8)
(IC-T81)
(IC-T81)
(IC-T81)
(IC-U16)
(IC-U2AT)
(IC-V8)
(IC-V8000)
(IC-W21)
(IC-W21)
(IC-W21)
(IC-W21)
(IC-W2A)

TX Mod for the IC-T8a English language
Sensitivity for the IC-T8E after freq modification English language
Cellular mod English language
IC-T81 AM/FM/Wfm function English language
IC-T81 Frequency Expansion English language
ICOM IC-T81A Cellular Mod English language
How to program the ICOM-U16 English language
Extended TX mod for the Icom IC-u2AT English language
IC-V8 MOD for expanded RX/TX range. (136 – 174MHz) English language
v8000 gne caper English language
Receive only expansion for IC-W21 English language
Transmit expansion for IC-W21 English language
Full cross band repeater operation English language
Band expansion 50-999 MHz for IC-W21 English language
IC-W2A Expand frequency English language

(IC-W2A)
(IC-W2A)
(IC-W2A)
(IC-W2A)

IC-W2A Cross Band Repeat Function English language
IC-W2A Extended Transmit Mod English language
IC-W2A signal level English language
IC-W2A Weak transmit audio English language

(IC-W2E)

IC-W2E Expand frequency English language

(IC-W31)
(IC-W31)
(IC-W31)
(IC-W31)
(IC-W31)
(IC-W31)
(IC-W32)
(IC-W32)
(IC-W32)
(IC-W32)
(IC-W32)
(IC-W32)
(IC-X2A)
(IC-Z1A)
(IC-Z1A)

IC-W31E Frequenzbereichs-Erweiterung German language
IC-W31E CROSS-BAND-REPEATER German language
IC-W31 RX Mod English language
RX/TX expand for ICOM IC-W31E English language
IC-W31 RX mod part 2. English language
Cross Band Repeating with the Icom IC-W31A English language
Expanded Frequency Coverage on TX/RX for the Icom IC-W32A/E English language
Crossband repeater and extended RX/TX mods English language
To extend the receiver and open up 800 MHz receive (cellular blocked) for IC-W32A English language
IC-W32 TX modification. Only a picture. English language
ICW32 E Crossband repeater German language
Icom IC-W32A programming glitch English language
Cross Band Repeat Function for the ICOM IC-X2A English language
IC-Z1A Extended Receive English language
IC-Z1A 800-900 MHz Receive English language

(IC-Z1A)
(MISC)
(MISC)
(MISC)
(MISC)
(MISC)
(MISC)
(MISC)
(PS85)
(R-1)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)

Pictures for the two modification above English language
ICxx71 ram adaptor for use with eprom programmer English language
BNC connectors for ICOM HTs replacement English language
CAT interface for any ICOM English language
Reset ICOM radios English language
Use ICOM SM-20 Mic to Yaesu ,Kenwood, etc. English language
Icom Hex Addresses English language
QRP mod for ICOM transceivers English language
ICOM PS85 fan modification English language
R1 (and IC-nSAT) Owners Note English language
Examining the icom ic-r7000 receiver English language
Cool your R-7000 receiver with another heat sink English language
Add a cooling fan to your R-7000 receiver English language
TV interface for R-7000 English language
198 channels for your R-7000 English language

(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-7000)
(R-71)
(R-71)
(R-71)
(R-71)

Modify your ICOM R7000 to scan and search faster English language
A low cost panadaptor for the R-7000 English language
The frequency displayed and actually received are not the same English language
The S-meter may not drop to 0 when recieve 500-800 MHz English language
Increase the number of memory channels to 200 English language
The remote relay sometimes stays energized English language
To improve audio quality in SSB operation English language
If display fails to operate at power on English language
R-7000 Display/Sensitivity Problem English language
IC-R7000 scanning improvement English language
Intermittent display English language
Tricking the ICOM R-71A to tune below 100 KHz English language
Modifications to the Icom R71A IF filter selection circuit English language
Here is the R-71 version of the Drake R7/R8 type passband tuning system English language
R-71A Memory Notes English language

(R-7100)
(R-7100)
(R-8500)
(SM-20)

Modify your Icom R7100 to provide an output directly from the discriminator English language
Icom R7100 Discriminator Mod English language
Operating the Icom R8500 in other contries English language
Icom SM-20 desktop microphone wiring English language

31-01-2000

(AH-4) Icom, AH-4, AH-3 ( automatic antenna tuner ) connection to any radio.

Author: AA7OL Niko Takahashi - [e-mail]

Icom AH-4 and AH-3 ( automatic antenna tuner ) connection to any radio

Both AH-3 and AH-4 are similar

Here is a redesign of connection digram of the ICOM IC-AH3 and IC-AH4 by 5B4AEZ.

There is four wire control cable coming out beside coax cable.

Control cable has

White: Start tuning
Green: Tuning in process
RED: 12 V DC input
Black: GND

Tuning Process

1. Put about 10 watts of power into tuner. ( CW )

2. After about 0.5 second, press start switch for a moment. ( use momentary contact switch )

3. LED start blinking , which indicate tuning is in process.

4. After about 3 seconds or so, LED shut off, and tuning is completed,

If tuning is successful SWR should be less than 1.2

Some radio start to reduce the power when SWR is high, this tuner takes at least 10 watts of power for tuner to work properly.
Most of the 100 watts radio should not have any problem, since they still put out 10 watts or so, even with high SWR.

But, it does not work with some QRP radio ( 5 watts or less ).

Adjust power level, if necessary.

You may extend control cable to 100 feet , it still work fine, you can put this tuner on top of tower.

Let me know , how it worked

[e-mail]

This modification is read 1503 times.

07-06-2001

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(AT-160) Using the AT-160 with the IC-706MKII

Author: Dave Abshire Sr. - KG4KOX - [e-mail]

ICOM's IC-706MKII transceiver and AT-180 antenna tuner are designed to work together. However, ICOM's AT-160 is a very
popular antenna tuner. Originally designed to work with the IC-728 and IC-729 transceivers (now out of production), the AT-160
will work with the IC-706MKII if the following instructions are followed:

1. (IC-706MKII only, not IC-706) The IC-706MKII will transmit on VHF constantly when connected to the AT-160. To stop this,
remove the wire attached to pin 6 of the DIN connector within the OPC-104 cable.

2. Open the AT-160 and make sure the switch labelled "S1" on the circuit board is switched to the bottom, shown as "IC­725/726" in the AT-160 instructions.

3. Make sure that the connections to the AT-160, using the OPC-319, OPC-104, or OPC-125C cables, are according to the AT­160 instruction manual. ICOM America suggests using the OPC-599 adapter cable for connection of the OPC-104 to the IC­706MKII.

4. Connect the radio to the transmitter terminal and connect an antenna to the ANT terminal. Make sure the antenna has less
than a 3:1 SWR. Place the radio in FM, AM or RTTY mode and key the mic. The AT-160 will now tune properly.

5. The tuning button on the front of the IC-706MKII will not operate when using the AT-160 antenna tuner. This feature was
designed to work with the AT-180.

6. Check the SWR presented to the radio. It should be less than 1.5:1. The AT-160 operates with the IC-706MKII as it would
with the IC-725 or 726 transceivers. Included with the AT-160 instructions is a page dedicated to the antenna tuner's
operation with an IC-725 and IC-726 transceiver. This is not the way the AT-160 operates with the IC-706MKII.

7. There is no way to turn the AT-160 off or place it into "thru" mode when operating with the IC-706MKII.

Date: 18-06-2001

User comment

From:

Dave KG4KOX

Subject: Extra note
I cut one end off the OPC-104 that came with the AT-160 and used the small 13 pin adaptor that came with the 706 MKII. NOW

you must leave pin 6 un-connected or your radio will stay keyed on 2 meters.

I did the mod and it works great on HF but I can't get it to tune proper on 6 meters, It will tune to a 1:1 then next time you
key up it will retune again. If anyone knows a way around this please let me know.

Dave
KG4KOX

This modification is read 711 times.

19-07-1998

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(AT-500) AT-500 Automatic Antenna Tuner Modification

I have been using the icom at-500 automatic antenna tuner for six months, and it is a great piece of gear. however, there is a
very minor modification i performed to the tuner to better suit my needs.

The tuner automatiacally selects one of four antenna s0-239 connectors on the back depending upon which band you are
operating. Many of us utilize one feed line for an 80 and 40 meter dipole or inverted vee. The at-500 (and at-100) has two
seperate antenna terminals for these bands. If you desire to use one feed line for both of these lower band antennas, you either
have to install a coax switch and manually switch the tuner in line, or unscrew the pl-259 connector from one antenna terminal
and install it on the other. All of this is inconvenient and defeats the purpose of an automatic tuner.
The mod i performed is extremely simple. I moved the wire going to antenna terminal #3 and moved it to terminal #2. This
directs the 80 meter rf to the same terminal as the rf for 40 meters and allows one to use the same antenna terminal for both
bands and one feed line. To perform the change, remove the top cover of the tuner, locate the two correct terminals using page
6 of the manual, unsolder the one to be move, and solder it to the correct terminal. The terminals are easy to reach.
Just be sure all connections are good.

This modification is read 912 times.

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21-10-1999

(AT-500) ICOM AT-500 Tuner Hint

Author: Dave Parlier - [e-mail]

10/12/99
The IC AT-500 Auto Tuner has four (4) antenna coax plugs on the rear for various bands.
You can solder all band wires needed to a single terminal lug and use only one (1) coax connector, if desired (per ICOM user
manual). If you prefer not to "go inside" , then two short coax pieces fed into a "T" coax connector will feed two separate
frequency ranges (e.g. 80m & 40M) into a single connection point.

Dave Parlier W2CGG
Chatham, NJ

This modification is read 822 times.

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19-07-1998

(I290) Icom I290 scan modification

The objective of the modification is to implement a delay before scanning restarts when, in SCAN-STOP mode on BUSY
frequency, the received signal disappears.

The modification will then allow a frequency to be free for a while before scanning resumes.
With this modification, it will be given a chance to a signal to come back within a few seconds before the scanning restarts.
Now multiple QSOs or poor signals won't be truncated any more because of a too much impatient scanning !

WHAT TO DO:
Very simple. On the SENSOR UNIT, just solder a jumper between:

● the unused contact of switch S3 (the one corresponding to the TIMER OFF position of the circuit commanding the SEL pin of

IC1)

● and the EMPTY signal of connector J3 (this is the extreme pin nearest S2 on the SENSOR unit)

ATTENTION, there are some errors on the electrical scheme that I possess reference A-0488 :

● The S3 switch is represented in position TIMER OFF and not ON as written. You have to reverse labels OFF and ON.

● The signals BUSY and EMPTY on connected are reversed. EMPTY (SQ1) is on the extreme left pin of S3 and BUSY is on 2nd

pin of this connector S3. In fact, the switch S2 is drawn in the BUSY position and not EMPTY.

HOW IT WORKS :
The TIMER starts when pin SEL of IC1 goes to 0V. When the TIMER is running, the scanning is halted.

The scanning also stops when the BUSY signal is low level (0V) on pin SQL of IC1.
Let us suppose that a signal is received. Then BUSY goes to 0V and scanning halts. At the same time the EMPTY signal , which is
the inverse of BUSY, goes to 5V and the TIMER remains off.

If the received signal disappears BUSY goes high and EMPTY low, then the TIMER is enabled and starts running. It also maintains
the scanning in halt mode.

If, at the end of the TIMER delay, no signal has come back then the scanning restarts.
If a signal comes back before the end of the TIMER delay then the BUSY signal returns to 0V and maintains the scanning in halt
mode. In the meantime the TIMER will run until the end of its delay without any action on the process.

The TIMER delay is chosen with the R32 potentiometer on the SENSOR UNIT. The minimum value is about 4 to 5 seconds which
is perfect for this working mode.

Small modification .... great effect !

Gabriel F6DQM @ FF6PTT.FRPA.FRA.EU

This modification is read 407 times.

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19-07-1998

(IC-02) Band expansion modification for IC-02AT

FOR SERIAL NUMBERS ABOVE 34000

BY LTC STEVE PETERS, CAP

1. Remove back from radio (5 screws) and bottom plate (4 screws).

2. Carefully remove radio chassis from front case by pulling out top of radio and lifting slightly (to remove battery contacts
from bottom case). Be extremely careful of ribbon cable and heat sink compound on power amplifier module.

3. Remove diode D2 from matrix board.

4. Add diode D4 (any small diode 1N4148; 1SS211

5. The following is a schematic of the matrix board:

ADD D4 REMOVE D2
I--+ --+-- --+-- +
V D4 ID3 I ID2 I D1
I I I I I
+ + +---+ +---+ + +

6. Install radio chassis back into front cover. Leave back off temporarily.

7. Carefully apply power to radio and enter the lowest desired frequency.

8. Adjust slug through bottom hole on VCO corr for .5 VDC at VCO test point (just below VCO shield) at lowest desired
operating frequency.

9. This completes the modification. A few words of caution: 1. The radio is not type accepted for use in the commercial band.

2. Make sure you reinstall the battery latch correctly on bottom of radio or battery will become permanently locked onto
radio. 3. Tighten screws on bottom of radio snuggly. If they loosen while battery is connected you cannot remove the
battery. (This has happened to any units and it would be prudent to periodically check these screws to assure their
tightness.)

This modification is read 1612 times.

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19-07-1998

(IC-02) Audio modification for IC-02 AND IC-04

This audio mod works on the 02 and 04AT. It increases the level of audio, as well as rolling off some of the lows. Sounds real
nice. It involves the circuit around Q105.

1. Replace C119 with a .01 uF cap (disc ceramic is fine).

2. Parallel R131 with a 1 uF cap (use a tantalum cap).

3. Parallel R132 with a .01 uF cap (disc ceramic is fine).

This is not the same mod as the one International Radio is advertising, which involves changing C117.
I tried an AB-1 Audiolaster from Engineering Consulting, and was very unhappy with the results. I am very pleased with the

audio given by this mod (much cheaper too!).

This modification is read 1146 times.

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19-07-1998

(IC-02) IC-02A Modified PLL rigs

The modification to the IC-02A to increase the receiver is fairly straight forward although a little delicate. The programming
diodes are located on the board directly behind the front panel, and are located in the corner of the board. They are little
rectangular black three leaded devices.

The proceedure to modify the radio is as follows:

1. Remove diode D2 - use a very small iron and solder wick to remove most of the solder, then lift the diode GENTLY while
heating the single tab side. After getting the first tab free, proceed to the other two tabs, lifting them one at a time. Do
NOT use a large iron or too much heat.

2. Take the diode and locate in the position labled D5. Carefully solder the diode in place.

3. Reassemble the radio except for the back.

4. Program the radio to the local weather channel (162.400 or 162.550) in the following manner: 6 2 4 0 0 or 6 2 5 5 0

NOTE:

the programming proceedure now requires that you enter the ten's of Mhz when entering a frequency.

5. Look at the back of the radio. In approximately the center of the exposed board is a metal can with two adjustments. The
top adjustment is a metal screw (actually a trimmer capacitor) while the bottom adjustment is a black slug with a small
rectangular adjusting slot

6. With the squelch open, adjust the lower black core counterclockwise approximately 1 1/4 turns until you receive the
weather station. As soon as you receive the weather, STOP turning the adjustment.

7. Replace the back on the radio and you are in business.

With this modification, the radio will tune from 140.000 Mhz to something over 162.550 without difficulty. Just remember that
you must enter the ten's of Mhz when entering a frequency. This modification does not affect the transmitter which still covers

140.000 to 151.995 Mhz.
Please note: This mod does not retune any of the RF stages of the receiver so the sensitivity is down some at the weather

frequency, however, I have no difficulty receiving it at thirty to forty miles.
I do have the ICOM service manual on the IC-02A. I purchased it from Delaware Amateur Supply at a local hamfest several

weeks ago.
According to the manual, the VCO on the PLL should cover 25 Mhz. minimum.

This modification is read 1203 times.

19-07-1998

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(IC-02) Low audio speaker mike on IC2A, 3A, 4A OR 02AT

If you own one of the IC2A, 3A, or O2AT series Hand-helds, you may be interested in reading on. I know my hearing is pretty
good, but have you ever tried to listen to the audio coming out of your speaker mike on the above ICOM's? For the most part,
it's pretty low. I may be the last guy to figure out a cure for this, but here it is anyway. On the O2AT, etc., there is a groove on
the back near the top of the rig that is just the right size to accept the HM9 speaker mike turned 90 degrees so that the mike
plug fits in that groove in the rear of the rig. Thus alllowing all the audio to be heard from the internal speaker of the rig, usually
much better than the speaker mike.

Now, in the case of the 2A series, etc., the fix is more complex. These rigs don't have that handy groove built in, so I decided a
groove had to be made to accept this configuration. I thought long and hard about a minute, before getting the "Dremel" out and
making my own slot or groove. It works well on both hand-helds I have. In fact, you can hook up an external speaker for even
more loudness in the auto. So, give it a try or see me for a demo.

This modification is read 1034 times.

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19-07-1998

(IC-02) ICOM 02/03/04 & Vox Unit

The ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supply
options.

The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using the
resistor or resistor/capacitor interfaces suggested in some manuals.

I am using the ICOM HS10-SA Vox unit to interface the ICOM 02/04 AT here.It has worked somewhat well for some time but I
was always plagued with a MINIMUM 200 msec transmit "hang " delay until I tore it apart for examination and correction.

The small " delay " pot on the front of the unit is in series with a 2.2 Megohm resistor (R-19 on the board). The adjustable pot is
also about 2 megohms as well. This combination allows a MINIMUM VOX "hang" transmit delay of 200 msec.

By identifiying the solder connections for R-19 on the back of the PC board and placing a low value resistor ( or jumper ) in

parallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISE

position. The minimum 200 msec delay has been defeated.

This modification is read 1050 times.

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19-07-1998

(IC-02) Another band expansion mods for Icom IC-02

The following method of modifying the Icom IC02 is an alternate to the IC02.MOD file. This one should give you PL out of band
without jumpering 5 VDC to the tone chip. Use 1N914 or equivelent when adding diodes.

1. On the logic matrix, remove D402 and D403.

2. Add D402, D403 and D404 with the cathode at 4 o'clock and the anode at 12 o'clock.

3. Retune the VCO to cover your desired frequency spread. My 02AT did not want to go beyond 163 MHz. I have a friend
whowas able to get his to the low 170s.

4. To jump from 140 to 150 or from 150 to 160 (or vice versa) you must "tune across" the boundry, in the same way that you
do for an unmodified 02AT. For example, key in 149.995 and then move up until you are in the 150s. You can then enter
any 150 MHz frequency (starting with the MHz).

This modification is read 1387 times.

19-07-1998

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(IC-02) For increased receive audio and improved response

Solution: Remove C117. C117 is a .22 uf capacitor. It can be located by first finding the 8 pin IC that is neart the middle of the
"Main Unit". Looking immediately above it (above pin 4) untill you see 2 round polarized capacitors. The one on the left is C117.
It can be successfully removed by just bending it back and forth untill the leads break. Be carefull to get the right one!

This modification is read 1051 times.

19-07-1998

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(IC-02) To increase the memory scan and search scan speed

Solution: Install a 100k ohm resistor across R413. To locate R413 Remove the DTMF Board that is attatched to the inside front of
the radio by removeing the two small screws. You will now have the logic unit exposed. IC401 (which is the postage stamp sized
IC near the middle of the board) is easily visible. Locate the bottom right corner of this device and continue down until you come
to the first micro chip resistor. This is R413. Carefully install a 1/8 Watt or smaller 100K ohm resist or across it.

This dramatically increases the scan speed but also raises the "BEEP" tone frequency.

This modification is read 1082 times.

19-07-1998

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(IC-02) ICOM HS-10SA VOX for IC-02AT Mods

The ICOM headset VOX model HS-10SA for the IC-O2AT can be a handy unit for mobile use but it has a serious limitation as it
comes from the box. There is no way to turn it off other than unplugging it! This means any conversation with a passenger,
cough or sneeze goes out over the air.

Fortunately there is any easy remedy. Remove the 3 screws holding on the rear cover and the single screw holding the circuit
board. Carefully lift out the board and locate R23. It is a 4.7K 1/8 W resistor located near the lower edge of the board.

One end of it connects to the white lead of the cable to the HT. The other end connects to the collector of Q7. This is the keying
circuit. In normal operation, Q7 is saturated when the VOX is active. Since the emitter of Q7 is grounded, R23 is effectively
connected from the white lead to ground, keying the HT. Carefully unsolder the end of R23 which goes to Q7 and lift this lead
out.

Drill a 1/4 inch hole in the center of the end of the case and mount a SPDT switch. The switch the author used was a C & K 7207
which is a 3 position, center off, SPDT, with one side spring return momentary and the other side latching. This allows the
momentary side to be used to key the HT manually, the latching side for the VOX operation, and the center OFF.

Now connect the center pole of the switch to the end of R23 which used to go to Q7. Connect the latching side of the switch to
the hole in the board where R23 was (Q7) and the momentary side of the switch to ground (shield of cable to HT). Now
reassemble the unit and test.

This modification is read 1015 times.

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19-07-1998

(IC-03) ICOM 02/03/04 & Vox Unit

The ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supply
options.

The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using the
resistor or resistor/capacitor interfaces suggested in some manuals.

I am using the ICOM HS10-SA Vox unit to interface the ICOM 02/04 AT here.It has worked somewhat well for some time but I
was always plagued with a MINIMUM 200 msec transmit "hang " delay until I tore it apart for examination and correction.

The small " delay " pot on the front of the unit is in series with a 2.2 Megohm resistor (R-19 on the board). The adjustable pot is
also about 2 megohms as well. This combination allows a MINIMUM VOX "hang" transmit delay of 200 msec.

By identifiying the solder connections for R-19 on the back of the PC board and placing a low value resistor ( or jumper ) in

parallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISE

position. The minimum 200 msec delay has been defeated.

This modification is read 462 times.

19-07-1998

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(IC-04) ICOM 02/03/04 & Vox Unit

The ICOM Family of Hand-Held Radios (02/03/04 AT) are well suited for packet radio given the many available power supply
options.

The big problem is getting the PTT to operate " CLEANLY " while not compromising the audio level from the TNC when using the
resistor or resistor/capacitor interfaces suggested in some manuals.

I am using the ICOM HS10-SA Vox unit to interface the ICOM 02/04 AT here.It has worked somewhat well for some time but I
was always plagued with a MINIMUM 200 msec transmit "hang " delay until I tore it apart for examination and correction.

The small " delay " pot on the front of the unit is in series with a 2.2 Megohm resistor (R-19 on the board). The adjustable pot is
also about 2 megohms as well. This combination allows a MINIMUM VOX "hang" transmit delay of 200 msec.

By identifiying the solder connections for R-19 on the back of the PC board and placing a low value resistor ( or jumper ) in

parallel....I was able to achieve a ZERO "hang" transmit delay time with the delay pot in the FULL COUNTER-CLOCKWISE

position. The minimum 200 msec delay has been defeated.

This modification is read 588 times.

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19-07-1998

(IC-04) Out of band modification for IC-04

1. On the logic matrix, remove D402.

2. Add D402, D403 and D404 with the cathode at 4 o'clock and the anode at 12 o'clock. (You may use any signal diode such
as 1N914)

3. Add D405 with the cathode at 8 o'clock and the anode at 12 o'clock.

4. If you have a newer 04AT, the VCO cover will have holes in it that allow access to the tuning coils. If you have an older
04AT you will have to cut a hole in the VCO cover using a pair of small diagonals (be careful!).

5. Retune the VCO to cover your desired frequency spread. My 04AT goes from 441 to 473 MHz, which is pretty good.

6. Any frequency may be entered directly on the keypad (starting with the 10 MHz digit).

This modification is read 673 times.

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19-07-1998

(IC-04) Audio modification for IC-02 AND IC-04

This audio mod works on the 02 and 04AT. It increases the level of audio, as well as rolling off some of the lows. Sounds real
nice. It involves the circuit around Q105.

1. Replace C119 with a .01 uF cap (disc ceramic is fine).

2. Parallel R131 with a 1 uF cap (use a tantalum cap).

3. Parallel R132 with a .01 uF cap (disc ceramic is fine).

This is not the same mod as the one International Radio is advertising, which involves changing C117.
I tried an AB-1 Audiolaster from Engineering Consulting, and was very unhappy with the results. I am very pleased with the

audio given by this mod (much cheaper too!).

This modification is read 564 times.

19-07-1998

top of page

(IC-04) Low audio speaker mike on IC2A, 3A, 4A OR 02AT

If you own one of the IC2A, 3A, or O2AT series Hand-helds, you may be interested in reading on. I know my hearing is pretty
good, but have you ever tried to listen to the audio coming out of your speaker mike on the above ICOM's? For the most part,
it's pretty low. I may be the last guy to figure out a cure for this, but here it is anyway. On the O2AT, etc., there is a groove on
the back near the top of the rig that is just the right size to accept the HM9 speaker mike turned 90 degrees so that the mike
plug fits in that groove in the rear of the rig. Thus alllowing all the audio to be heard from the internal speaker of the rig, usually
much better than the speaker mike.

Now, in the case of the 2A series, etc., the fix is more complex. These rigs don't have that handy groove built in, so I decided a
groove had to be made to accept this configuration. I thought long and hard about a minute, before getting the "Dremel" out and
making my own slot or groove. It works well on both hand-helds I have. In fact, you can hook up an external speaker for even
more loudness in the auto. So, give it a try or see me for a demo.

This modification is read 556 times.

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19-07-1998

(IC-04) TX delay may be excessive at low temperatures

Model: IC-04AT

Division: Amateur

Note: This service bulletin is meant for technical per­ sonnel with experience working on solid state com­ munications equipment. Damage caused by im­ properly installing this modification may cause
ICOM to charge for subsequent repairs to the
product. ICOM does not warrant this modification.

Bulletin #: 02988-002

Date: January 1, 1988

Subject: Transmitter delay may be excessive at low tempera­ tures (can be up to 2 or 3 seconds).

Procedure

1. Remove the front and rear covers.

2. Remove the volume and squelch knobs by pulling up on them. Push down the high/low power and lamp switch. Remove the
four screws in the metal chassis corners. Unfold the chassis.

3. Replace R262 (currently 560K) with a 2.2 Meg resistor (ICOM P/N 915-01277).

4. Reassemble the radio.

This modification is read 553 times.

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19-07-1998

(IC-04) IC-04E fuer 9k6

Hallo,
hier nun ein Gif-Bild, aus dem man die Einspeis/Abgreifpunkte für 9k6 ersehen kann.

Ausführlichere Erklärung (Um das Gehäuse
zu öffnen schraube man...) spare ich mir, da ich jedem Amateurfunker soviel Geschick zutraue..hi Das ganze funktioniert ganz
gut, allerdings sind noch keine Langzeit- erfahrungen bekannt.
Gewährleistung, welcher Form auch immer, wird natürlich nicht übernommen.

This modification is read 594 times.

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01-04-2001

(IC-1200) Expanded RF 870 - 960 MHz for ICOM IC-1200

Author: John kb2ljj

1. Remove power and antenna.

2. remove screws and open the radio.

3. Locate and CUT resistor R-52 on logic " A " unit.

4. Install NEW antenna connector to position J2 on RF board. Note: a different antenna is required for the 870-960 bands.

5. Reassemble the radio.

6. Reset the microprocessor. ( Hold down the tuning control and Turn the power ON ) or ( Insert a toothpick in hole in the
corner of the bottom cover.)

Adjustement: R-8 Low TX power and Hi TX power All the MODS are captured by Packet. KB2LJJ

73s John kb2ljj

This modification is read 353 times.

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19-07-1998

(IC-1271) VOX of an IC-271,471,1271 usable for FM

How to make the VOX of an IC-271,471,1271 usable for FM :
1'st type of "main-board" :
The only thing to be done is to add a diode such as 1n4148 or bax13 on the MAIN board on the position D74

When D74 is inserted ... the vox works in FM also.
The diode is on the shematic diagram of the Main board but is not mounted on the pcb in the factory.

73's de stefaan
ON4BY @ ON4HU
16/03/1990 18.31 h

2'nd type :
(On this board a D74 is present (near PA- and RF-YGR- Unit))
(It might be not present in the plans !)

Disconnect the cathode of D69 from it's old postition. It's new position is the cathode of D50 or D51

name ! position on main board ! (old) function !
D69 ! near "CW-DELAY". ! "FM -VOX-OFF" ! FM 8V
D50 ! near "RF-YGR-Unit" ! "USB-VOX-ON" ! USB8V
D51 ! near "RF-YGR-Unit" ! "LSB-VOX-ON" ! LSB8V

20/03/1990 16.52 h

This modification is read 572 times.

30-03-2001

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(IC-1271) RAM Card Backup Battery Replacement Instructions

Author: ICOM

In the early 1980s Icom America marketed a group of transceivers and radios that utilized the latest state-of-the-art computer
technology to enhance the operation of the radios. This technology improvement allowed hams to afford a reasonably priced high
performance transceiver which until then was only available on units costing much more. Features now available to the hams
included: higher frequency stability, better frequency resolution, digital frequency display, almost instant recall of saved
frequencies (memory channels), quick mode signal processing and built in tones and offsets for the rapidly emerging repeater
operation.

Implementation of all these features required a CPU with associated logic circuitry. In the early 80s, the most cost effective way
to implement data processing and memory functions was through a DRAM (Dynamic Random Access Memory) to control the
CPU. This DRAM was a volatile memory integrated circuit which required a lithium battery to retain its instruction set. The
following receivers and transceivers had such RAM units:

IC-271 ; IC-471 ; IC-1271 ; IC-745 ; IC-751/A ; IC-R71A

The lithium batteries in these units typically lasted about 5 to 7 years before replacement was required. This was specifically
noted in each of the Owners Manuals for the products.

This lithium battery can be replaced by the radio owner if care is used. The following is a recommended procedure to accomplish
this:

Procedure

1. Disconnect the power cable from the radio, and take the cover off.

2. Unplug the RAM board and remove it from the radio.

3. Temporarily solder a 3 Volt DC battery source across the existing battery terminals (see suggested connection points on the
circuit board pictures).

4. Unsolder the old lithium battery and replace it with a new one. (BR2325 1HC, ICOM stock number 945 03112)

5. Unsolder your temporary 3 Volt DC source.

6. Reinstall the RAM board into the radio.

Cautions

1. Do not use an AC powered 3 Volt DC source, your grounded soldering iron tip could short out the battery (+) terminal. Use
a 3 Volt battery DC source only (2 alkaline cells for example).

2. Do not solder the external DC wires directly to the lithium battery tab pads. If you do so, you will not be able unsolder the
battery without having the wires drop off.

3. If by accident you lose power to the RAM unit it must be sent to Icom America for reprogramming.

4. Be careful not to damage or bend the connector pins on the radio side while removing or reinstalling the RAM card.

Pictures

There are two versions of the ICOM RAM boards. Both are identical in operation, and they are interchangeable. The differences
are in the circuit board layouts only. Note that the black and red wires visible on these images are the suggested way of
connecting the external DC backup voltage while the battery is being replaced. The wires are not a part of the RAM card, and
should be removed when the battery replacement procedure is complete. Refer to the replacement procedure outlined above.

RAM card version A images:

RAM card version B images:

This modification can also be found at ICOM's own homepage on the following URL: "RAM Card Backup Battery Replacement

Instructions"

This modification is read 595 times.

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19-07-1998

(IC-1275) IC-1275 Freq. steps mod

Titolo: Tuning steps change for all mode Icom IC-275/475/575/1275
The IC-275/475 FM-Step selectmatrix use these diodes on the front unit: (type 1SS53) D41, D42, D43, D44, (D45), D46
Note: diode D45 is not present but solder holes exist for it on the board just between D44 e D46
installed diodes are marked with X :

(*) (*)
D41 D42 D43 D44 D45 D46 D48 Steps DB4 DB5 DB6 DB7

. . . . . . . 10.0 Hz

. . . X . . . 100.0 Hz 1 0 0 0

. X . . . . . 1.0 KHz 0 0 1 0

X . X . 5.0 KHz 1 0 1 0

. . . . X . . 10.0 KHz 0 1 0 0

. . . (*) X X . 12.5 KHz (*) 1 1 0

. . . . . . X 25.0 KHz 0 0 0 1

X . X . . . . 1.0 MHz 0 1 0 1

(*)
To set a step of 12.5 KHz in FM mode (TS button off) it is not necessary disconnect the diode D44, just insert the diode D45
(IN4148 or similar) near D44 and "voil? les jeux sont faits".
Unscrew the two lateral screws and unlock the front panel.
Remove also all the connectors of the front board and after that unscrew ALL the screws of the metallic shield covering the front
board. It seems too much complicated insert the diodes from the component side of the front board, so it is better insert D45
from the solder side.

This modification is read 537 times.

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27-10-1998

(IC-1275) Power control modification

Problem:
The power control circuit in IC-x75 is an ALC circuit. ALC circuits suffers from several drawbacks:

● slow reaction time due to time constants

● insufficient regulation due to low feed-back factor

These factors gives the problem that if the average power has been set to a low value (e.g. for driving a HPA), peak power can
still be in the order of 3-4 dB higher. This leads to either considerable side band distortion or a low average power output.

note: If you are always using your transceiver barefoot, without connecting any PA or transverter, this modification will offer no
benefit.

Solution:
The solution to these problems is to use a simple forward gain regulation without the feed back circuit of the ALC. The original

ALC is still kept for SWR protection only.
The ALC is working on gate 1 of Q13, which is a IF amplifier (9 or 10.75 MHz). The new power regulation uses gate 2 of Q13.

Therefore the two circuits can exist in parallel.
The modification should also give you a bigger dynamic range in the power regulation (lowest power < 5W on the IC-x75H).

Implementation:

● replace R87 (470k) with 100k

● cut "POCO" wire (pin 3, P1/J1, MAIN, orange) at the plug (P1)

● connect the "POCO" wire to gate 2 of Q13 (e.g. via top of R87)

● adjust R250 (SWR protection), R256 (low power level) & R259 (high power level) fully counter-clockwise. (this will give you

full SWR protection, but cancels the ALC in normal operation).

● put the front plate RF PWR in full output position (clockwise) and adjust R82 (Q13 output attenuator) until you have the

nominal output power (initially the output power will be higher because you removed the regulation, but the PA will be
saturated).

● the balance between FM, CW & SSB output can be adjusted with R137 (CW carrier level) & R105 (FM carrier level).

● other interesting adjustments: R135 (mixer balance i.e. SSB carrier suppression), R133 (TX BFO output level).

This modification is read 535 times.

27-10-1998

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(IC-1275) Restoration of pass band tuning

Problem:
ICOM has chosen to remove the PBT in the later models, and replace it with a "data level adjustment". This change removes the

possibility to profit from the PBT in case of QRM or to use the PBT as a cheap CW-filter.
Furthermore the two extra IF-mixings is done with only a minimum of filtering, making the receiver very susceptible to spurious

IF breakthrough. This is often heard as high-pitch tones or as a high IF noise level.
Solution:
The solution is to re-wire the "data level" potentiometer so that it adjusts the PBT VXO-oscillator, and to re-install FI3. FI3 is a

455kHz ceramic SSB filter and can be bought under the type number: MURATA CFJ 455 K6.
Implementation:

● remove the capacitor (C61) fitted in place of FI3

● solder in FI3

● readjust R72 for proper IF gain

● cut wire PBTV (pin 4, P1/J1, MAIN, yellow) about 5cm from the plug (P1)

● cut wire AMO2 (pin 3, P2/J18, MAIN, red) close to the plug (P2)

● cut wire AMO3 (pin 4, P2/J18, MAIN, metal baird) close to the plug (P2)

● connect PBTV wire (the end not connected to the plug) with AMO2 wire (the end not connected to the plug)

● connect AMO3 (the end not connected to the plug) to +8V e.g. by tapping (pin 1, J4, MAIN, brown).

● connect the wire stubs on the plug (AMO2 & AMO3) together is you wish to use external modulation input for PACKET etc.

● adjust the coil next to X2 (PBT VXO) for correct middle PBT setting

This modification is read 520 times.

27-10-1998

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(IC-1275) Splitting into RX- and TX paths

Problem:
This is a general transceiver problem. If you want to use the transceiver as part of a bigger setup (i.e. with external PA &

preamp or with a transverter), it is convenient to have separate access to the RX and the TX of the transceiver. Otherwise you
need two coaxial switches every time you add a new accessory. With split RX/TX paths you only need one switch - at the
antenna. Furthermore split RX/TX paths eliminates the need for a change-over sequencer.

On the other hand it is also nice to have the transceiver working normally when you are using it barefoot.

Solution:
The solution is to jump wire the RX path (between RX and the RX/TX switching) trough the rear side of the transceiver with 2

BNC connectors. In normal state these connectors are connected via a short cable. In case you need to "split up" the transceiver,
you remove the short coax cable, and you obtain direct access to the RX. The TX is still available using the common connector.

note: If you are always using your transceiver barefoot, without connecting any PA, preamp or transverter, this modification will
offer no benefit.

Remove the back cover. If you place the holes for the BNC connectors next to and aligned with the two existing DIN-connectors,
then ICOM have left enough space on the inside for the connections. You can also add other desired outputs like a phono plug for
AF OUT.

The RX cable runs between J4 on the RF YGR PCB and the PA unit.
note: In my IC-275H the PIN-diode for the FM RF gain is shared with the RX/TX switch and placed in the PA unit. This means

that the control voltage passes through the RX cable.
Therefore the breaking of the RX cable will cancel the FM RF gain function (the SSB/CW RF gain is working on the AGC and is not
affected). The solution is to install a new PIN-diode (D5) on the RF-YGR PCB. The PCB has already room for it. To avoid short­circuiting the control voltage the jumper placed in stead of C86 on the RF-YGR PCB, should be replaced by a 1nF capacitor.

This modification is read 523 times.

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27-10-1998

(IC-1275) Modification of cw pass band (BFO)

Problem:
In these transceivers ICOM has chosen to shift the CW passband up 200 Hz compared to the SSB passband. This makes it more

difficult to copy SSB signals in CW mode.

Solution:
The extra BFO coil that is added in CW-R is short-circuited, and the BFO is re-adjusted for proper CW RX/TX-tracking and for

preferred USB/CW passband.

Implementation:

● short-circuit Lcw in the BFO compartment.

For readjusting the BFO you need another transceiver (TRX2) with correct tracking.

1. Receive on TRX2 and transmit in CW. Adjust the VFO (with the RIT off !) of TRX2 until you have the desired side tone in CW
mode. (e.g. 800 Hz - can be found by beating the tone with the side tone oscillator).

2. Transmit on TRX2 and adjust Ly (CW-R) until you have the desired side tone in CW mode. (you are setting the ~800Hz
difference between CW-R & CW-T).

3. Adjust Lx (CW-T) for preferred USB/CW receive passband.

You might have to repeat the tuning once again, as there is some interaction between the adjustments (diode switching for high
impedance RF circuits are not perfect !). If you would like to adjust the LSB passband, this should be done by adjusting the
capacitor C, before adjusting the coils.

Note: The BFO coils are switched in successively to give the required offset from the LSB frequency. Therefore adjusting CW-T
also changes USB/CW-R.

Re-adjusting all of the BFO frequencies is a good idea in any case to compensate for crystal aging. If the passbands sound
different in LSB and USB it is a sure sign of mis-alignment due to crystal drift - they should be more or less the same.

This modification is read 513 times.

27-10-1998

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(IC-1275) Disabling of SBB squelch

Problem:
Squelching is nice to have in FM mode, but it doesn't really work for SSB, where you will be looking for weak signals. Therefore

you have to adjust the squelch level every time you change mode. Furthermore I enjoy using FM as a monitoring mode on the
SSB calling frequency, so changing the mode happens quite often.

Solution:
The solution is quite simple. Just cut the connection to the SSB input of the squelch circuit in some way.

Implementation:

The easiest way to break the connection is to connect the base of Q7 to ground. The base is the lead facing into the centre of the
PCB.

Date: 04-01-2002

User comment

From: Hiroki Ohashi,JI2EVL

Subject: other methode for confortable ssb SQL

R18 (33k)on Main Unit change 68k. And You set SQL position between 9 and 10 o'clock. You can operate sql open on SSB
mode, and sql able on FM mode.
It align that FM SQL position to 9 O'clock from 10 o'clock.

This modification is read 522 times.

27-10-1998

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(IC-1275) Very fast AGC

Problem:
For some modes of weak signal communication, it can be desireable to have a very fast AGC (e.g. meteor bursts with a sharp

rise and a long weak "tail"). The standard fast AGC has a time constant of about 2 secs (!), which also means that a noise pulse
can mute you for quite some time.

Note: Never use the noise blanker when receiving high speed CW (Meteor Scatter). The noise blanker mistakes the high speed
keying for noise pulses, and will seriously corrupt the signal.

Solution:
The solution is to move the "AGC fast" capacitor (C19) to replace the "AGC slow" capacitor (C20). You will loose the "AGC slow"
option, but I find "AGC fast" adequate for most signals.

Another solution is to switch out the "AGC fast" capacitor (C19) seperately, but then you will get the problem of finding an
appropiate front plate switch. I already tried to use the DATA button, but it cannot be activated in CW.
Note: a strong signal will be seriously distorted in AGC OFF mode.

Implementation:

● remove C20

● move C19 to the replace C20

This modification is read 521 times.

27-10-1998

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(IC-1275) SSB RF Gain

Problem:
The RF GAIN function is different in FM and in SSB/CW modes. In FM mode the RF GAIN controls a PIN-diode at the input of the

preamp. In SSB/CW the RF GAIN simply activates the IF AGC.
The use of the preamp input attenuator (the PIN-diode) can be useful also for SSB/CW e.g. if you have connected a mast head

preamp with excessive gain. In this case the attenuator will help you to adjust the signal levels at the mixer, and thus reduce
intermodulation and blocking.

Solution:
The solution is to remove the SSB/CW RF GAIN for SSB/CW (this function is of little use anyway), and enable the FM RF GAIN

even in SSB/CW.

Implementation:

● Cut the lead (FM8V) conneted to (pin5, J6, potmeter PCB, green) about 4 cm from the plug

● Connect the short plug end with R14 (on the potmeter PCB) by soldering it to the end that is connected to the plug (+8V)

This will enable the FM RF GAIN in SSB/CW.

● cut R30 open

This disables the SSB/CW RF GAIN, and you now have a variable input attenuation with a dynamic range of 10dB (IC275 with
MI308/1nF) to 16 dB (IC475).

Note: The IC-275 might have a shared PIN diode for FM RF GAIN and TX/RX switching. If you choose to split up the RX/TX
paths, you must install a new PIN diode (MI301 or equivalent) on the RF YGR PCB to implement this modification. See the note
under the section dealing with spliting the RX/TX paths.

This modification is read 515 times.

27-10-1998

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(IC-1275) Tuning speed

The tunning speed is set to a defaults of 100Hz, 1kHz, 5kHz or 1MHz depending on front plate setting and mode. These settings
can be manipulated by D41 - 46 at the front plate. At least a setting of 10kHz is also available.

This modification is read 510 times.

27-10-1998

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(IC-1275) Frequency range & CTCSS tones

The IC-275 have capability to cover 138 - 174 MHz and the IC-475 has capability to cover 430 - 450 MHz. Because of hardware
restrictions they might not be fully up to specifications in all of the band, but an extended range can be interesting for e.g. use
with a transverter. It seems that the IC-275 has a parallel wide band preamp, that can be switch via the WBT pin on RF-YGR
PCB.

In the European versions the transceivers are wired for 1750 Hz repeater call, and they have no CTCSS capability. The
transceivers have a built-in CTCSS encoder, so these functions can be restored.

Both of these version dependent functions can be set by the diode matrix: D20 - D24 in the logic unit. I do not know the exact
mapping, but a lot can be derived from studying the different frequency ranges and the diode matrix coding table found on the
schematic diagram.

This modification is read 527 times.

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20-04-2000

(IC-1275) IC 475H / 1275E mod for 9k6 (G3RUH) use

This is original the 9600 baud mod for the IC-475H. Yann - F1NGP [e-mail] has reported this to
me.

I've tried the MODS for 9600bds for my ICOM IC-475H . Working OK . I've tried to build the same mod on my 23cm ALL-MODE
ICOM IC-1275E as the MAIN UNIT is the same as the 475 ... ALL WORKING OK !

Thanks to Yann.

The original ICOM IC-475H 9600 baud modification.

Warning:

I'm writing this message to help out owners of Icoms 475 H to modify their transceivers for use with a G3RUH modem. I will not
take any responsability if you destroy your transceiver while doing this modification. This modification requires that you have a
minimum experience in soldering and electronics. If you feel that you cannot undertake this modification, don't even try it and
leave it up to someone else!

Reception of FSK signal:

The reception has to be taken directly off the demodulator chip. This is the chip referenced as IC6 (MC3357P) on the electronics
diagram.
Demodulator output is on pin 9 of this chip. You will have to run a SHIELDED wire from this pin to the outside of your
transceiver. I've done this by connecting it to pin 11 of J4 (AQS socket on the back). This pin is originally unused. But this is not
as easy as it sounds; you will have to unscrew both sides of the transceiver and undo a lot of parts to finally solder on a very
small plug! Be careful here.

Transmission of FSK signal:

The FSK signal is simply injected on pin 2 of the AQS socket. BUT, as you will see on the electronic diagram, this signal goes
through a variable resistor (R152) and a capacity (C142). So you might encounter two problems: not enough and/or distorted
modulation. In my case, I used a MFJ 9600 Bauds card and I had to put the level almost to the maximum on this board, while
also putting the variable resistor to the minimum! The capacity on the other hand is very very bad for the modulation of the FSK
signal as the transceiver should respond to DC! My solution: simply short circuit the capacity (C142). This is most easily done
directly on the components side of the circuit board, since it's very difficult to take it out of the transceiver.

Other signals:

You will be able to put the PTT line to pin 6 and the ground to pin 1 of the AQS socket. You will also notice that on pin 13, you
have 13.8 V available. This can be used to power the TNC for example...

I have now a much more stable 9k6 signal than before, when I still had the C142 in the line. Although, this was reportedly been
working for other people, it simply didn't for me! Maybe you can avoid short circuiting the capacity, so try it first (although I
doubt it!).

I hope this will help somebody and if you have any more questions, don't hesitate to contact me at my homeBBS: HB9VBC @
HB9IAP.SROM.CHE.EU

This modification is read 527 times.

19-07-1998

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(IC-2) Modification For IC-2AT

If you have studied the schematic diagram for this radio, you will notice that pins 15 and 16 are not indicated on the
programmable divider chip IC1 (TC9122).
By simply connecting pin 15 thru a switch to pin 1, you will be able to move the radio up in frequency by 10 MHZ.

Some of these radios were sold without covering 140-150 MHZ.
The modification for this extended coverage is described below:

1. Open up the radio and locate the FLEXIBLE BOARD, this connects the thumbwheel switches to the MAIN BOARD.

2. At the MAIN BOARD end of the FLEXIBLE BOARD, add a jumper at location C4. There should already be a jumper at location
C2.

3. At the thumbwheel switch end of the FLEXIBLE BOARD, remove the jumper which connects C3 and COM.

4. Reassemble the radio. Coverage is now 140-150 MHZ.(MARS/CAP)

Now, if you activate the switch described above, the radio will now operate in the 150-160 MHZ range, after L3 adjustment,
described below.

OPERATION and L3 ADJUSTMENT:

1. Activate switch and dial up a known active frequency.

2. Adjust L3 until PLL locks up and radio begins receiving. (you need an active frequency to tell when this happens)

3. To return to 140-150 MHZ, repeat above steps with switch off.

NOTES and DISCLAIMER

1. Drill a hole in the case of the radio so that L3 can be adjusted from outside of the radio.

2. The above information is presented for educational purposes only, and is not an endorsement of any particular practice.

3. This MOD has been in operation for 6 years with no ill effects on the radio

4. This MOD courtesy N2MOD.

This modification is read 1316 times.

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19-07-1998

(IC-2) Low audio speaker mike on IC2A, 3A, 4A OR 02AT

If you own one of the IC2A, 3A, or O2AT series Hand-helds, you may be interested in reading on. I know my hearing is pretty
good, but have you ever tried to listen to the audio coming out of your speaker mike on the above ICOM's? For the most part,
it's pretty low. I may be the last guy to figure out a cure for this, but here it is anyway. On the O2AT, etc., there is a groove on
the back near the top of the rig that is just the right size to accept the HM9 speaker mike turned 90 degrees so that the mike
plug fits in that groove in the rear of the rig. Thus alllowing all the audio to be heard from the internal speaker of the rig, usually
much better than the speaker mike.

Now, in the case of the 2A series, etc., the fix is more complex. These rigs don't have that handy groove built in, so I decided a
groove had to be made to accept this configuration. I thought long and hard about a minute, before getting the "Dremel" out and
making my own slot or groove. It works well on both hand-helds I have. In fact, you can hook up an external speaker for even
more loudness in the auto. So, give it a try or see me for a demo.

This modification is read 1012 times.

19-07-1998

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(IC-2) ICOM IC-2AT internal antenna connection problem

I routinely use a half wave ant. On my IC-2AT handheld. When collapsed, the antenna has the same gain ( loss ) as a rubber
duck antenna while giving me greater range when fully extended.

There is a certain amount of movement of the center pin of the bnc connector with the half wave antenna on the handheld.
This movement causes fatigue fracturing of the wire connecting the printed circuit board to the bnc connector.
After numerous failures, i used the braid of RG-174 coax to make the connection.
First remove the bnc from the radio and brake off the non-used ground lug.

The pin of the bnc should beplaced into the end of the braid.
A thin pice of wire is then wrapped around the braid 3-4 times, and then secured, then soldered. Reinstal the bnc and dress the

braid to the solder pad on the printed circuit board and solder. Do not heat the braid to log while soldering, as solder will be
drawn up, making it stiff and subject it to fatigue fracturing...

This modification is read 1016 times.

19-07-1998

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(IC-2) ICOM IC-2GAT ext frq for Transmit

Out-of-band transmit mod for ICOM IC-2GAT handheld 2M transceiver
(copied from packet radio; origin unknown:)
Back side of display board:

_____________________________________
| D505
| D507 D504 ___
| ___ ___ |___| |
| |___| |___| -- + -­| D506 Q506 | |
| _o_------ _o_ | hole for
| |___| | |___| | on/off-vol
| o o | o o | control
| | | |__________________
| -----|<--------- |
| add diode: 1N914 or equiv. |
| |

Connect diode between top lead of D506 and lower right lead of Q506 as shown.
Notes:

D506 may be absent. If not, remove it.
Reset CPU if needed.

A friend did this and his IC-2GAT can now transmit 138 to 178 MHz (no RF power output measurements were made). He did no
retuning, and did not have to reset the CPU. He used a tiny axial-lead glass diode, replaced its leads with wire-wrap wire, and
encased it in shrink-tube. The operation requires a super-tiny soldering iron. Observe CMOS soldering precautions: Unplug the
iron and ground the tip before touching the circuit.

Remember: Except for MARS and CAP, it is illegal to transmit outside the ham bands with non-type-approved equipment.

This modification is read 1076 times.

19-07-1998

(IC-2) IC-2AT, If transmit RF indicator notwork properly

Model: IC Micro 2AT

Division: Amateur

Note: This service bulletin is meant for technical per­ sonnel with experience working on solid state com­ munications equipment. Damage caused by im­ properly installing this modification may cause
ICOM to charge for subsequent repairs to the
product. ICOM does not warrant this modification.

Bulletin #: 8988-002

Date: March 29, 1988

Subject: If transmit RF indicator is not reading properly

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Procedure

1. Disassemble the radio to gain access to the RF Board.

2. Replace the following parts on the RF Board:

Reference Original New ICOM
Designator Value Value P/N

Q309 2SA 1162 1SS 196 912-00965
D309 1SS 211 2.2Meg 1/8W
R345 Remove this part
C349 Remove this part

3. Reassemble the radio.

This modification is read 990 times.

19-07-1998

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(IC-2) Icom IC-2GXAT open RX

>David, For the IC-2GXAT receiver opening do the following steps as listed.
>
>1. Turn off the radio
>
>2. Press and hold the " Function, Scan and Dupe keys "
>
>3. While holding those keys turn on the radio.
>
>4. WAIT until the display returns to normal then continue to hold the
> keys for about 2 seconds
> after the display has returned to normal before releasing the keys
>
>5. The receiver is now opened up and will cover 138 to 179 Mhz or so.
> It WILL NOT do aircraft AM receive nor tune into that frequnecy range.

That's an interesting note. I recently did this to my rig (Purchased last may, low serial number) and it receives from about

50MHz to something like 204MHz continuously! Including the AM aircraft band.

This modification is read 1032 times.

23-08-1998

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(IC-2000) Icom IC-2000 Extended RX/TX Mod

Here's the mod for the IC-2000H 2-meter transceiver:
Using a hex wrench, remove the front of the face plate (NOT the main radio back!!) Turning it over, you will see the PC board.

Look for 16 solder dots like this:

O O OxO x = the offending diode that is begging to be destroyed....

O O O O

O O O O

O O O O

Taking a set of needle-nosed pliers (or the equivalent) snip the "x", dust off the PC board, and reassemble the radio. Do a
complete memory/factory reset which is described on page #38 of your IC-2000 series instruction manual Here's what's involved
in the CPU reset referenced above:

1. Push [POWER] to turn power OFF.

2. While pushing [SET] and [PG/CS-MW}, turn power ON

All LCD segments appear momentarily, the initial display appears and the tranceiver's CPU is reset.
This modification should take you less than one minute to accomplish. You will find your transmit capabilities expanded to 136-

174 Mhz.
Receive will remain at 118-174Mhz.

NOTE: It is strongly recommended that you purchase the following optional units:
UT-85 Tone Squelch Unit--allows pocket beep functions and tone-squelch receive operation--a must if one is plagued by stupid

paging tower inter-mod (a violation of the harmful interference laws...)
UT-101 DTMF Unit--provides pager and code squelch functions for selective call and silent standby, etc.
These extras are available for under $100 U.S. dollars. Highly recommended!!

This modification is read 1052 times.

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19-07-1998

(IC-207) Band expansion for IC-207

Remove the 4 screws ataching the bottom cover and remove the cover. (I had to use a small screwdriver to pry on the cover.
It's made to fit tight) with face toward you and belly up look to far right of board and close to you.

Locate a row of SMT diodes 3 on top then a shift to right and a few more. The three are in a PERFECT row top to bottom! count
from the top of the row 1 2 3.

Remove the # 2 & 3 diodes. Now continue looking down from there and you will see a resistor sticking up in the air (W14). Clip
the lead off of the resistor. Reassemble the radio and preform a CPU reset by holding the Set and S.MW buttons while turning
the radio on...(page 69 of manual).

You now will have :

118-135 RX (stock)
136-174 TX & RX
320-399 RX (hmmm whats there? I've heard a local radio station DJ
at a remote location talking to the station)
400-479 TX & RX
849-950 RX

The Transmitter will work and transmit at ALL of the listed TX freqs. and the power seems to be fairly broad banded and can
handle it... I now use my mobils as Ham AND GMRS. One less piece to lug around!

Date: 12-01-2002

User comment

From: anonymous

Subject: Icom 207H RX only Expansion

This modification will open up the RX coverage on the Icom 207H, while preventing out of band TX. This is useful if you need
UHF RX coverage above and below 440mhz ham band.

Simply cut the lead on resistor W14 (refer to the photo of the radio as submitted by others) Power up the radio, you do not
need to do a reset.

New RX coverage: 320-399.995 mhz Note: Holding the band button down for a second while on this band, will change the
detector to AM mode as noted by a decimal point appearing the right of the last digit. AM is used by Military Aircraft
communications. Latest band plan is 25khz channel spacing.

Coverage for UHF-FM is now 400.000-478.995
Simple Mod, no mess. Have Fun :)

This modification is read 2917 times.

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26-07-2001

(IC-207) Band Expansion for IC-207H

Author: Mike VK2ZOC - [e-mail]

When wanting to extend band TX for the IC-207H, follow the instructions for the IC-207. The variation is that there are only 2
diodes present, not the three described.

Remove BOTH of these. Also the resistor sticking up in the air near W14 has already been clipped. Note that these diodes are the
surface mount type so be careful when removing them.

Mike VK2ZOC

Date: 01-09-2001

User comment

From:

Mike VK2ZOC

Subject:
I've received a large number of emails from the US asking how you get the 850-950MHz band.

The modifications described don't give you extra bands that you don't already have. They remove the restrictions to TX in the
140-179MHz & 400-479MHz bands on the radio. Apparently radios from the US don't have the fifth (850-950MHz) band.

Mike VK2ZOC

This modification is read 3010 times.

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28-04-2001

(IC-210) Schematic of IC-210

Schematic of the ICOM IC-210.

Size: 1867 * 1355 = 265 Kb

Part 1 of 4

Size: 1867 * 1355 = 265 Kb

Part 3 of 4

Size: 1867 * 1355 = 245 Kb

Part 2 of 4

Size: 1867 * 1355 = 255 Kb

Part 4 of 4

This modification is read 321 times.

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21-03-1999

(IC-2100) Icom IC-2100H Extended Transmit Mod

For the first time anywhere on the web, the Icom IC-2100H extended frequency transmit modification and mod instruction sheet.

The socessor to the very popular IC-2000 unit, the IC-2100H has been around for a few months now and is selling for about
$200 at most hamfests. The unit uncludes PL encode/decode, and 55 watts out at high power. But up until now the modification
insturctions have been unavailable!

Brought to you by:

Spectracom Communications, for all your commerical radio needs call 732-989-1091 or e-mail to

[e-mail]

W3EAX, Amateur Radio Association at the U of Maryland
KB3CVD, UMBC Amateur Radio Club
And amateur stations KC2AEI and W2SJW.

Please give us credit when copying these instructions!

1. Hold down the second and third front function buttons while turning the radio on. Now turn it back OFF.

2. Carefully remove the large tuning knob and remove the two hex screws that hold the faceplate on. Pull the faceplate
straight of the body without tilting it (you run the risk of bending the pin connectors behind the faceplate).

3. Turn the faceplate over and locate the main ic chip, set at a 45-degree angle. Just to the lower left and right of the IC, you
will see the main pin connectors. Under the lower right corner of the left pin connector, you should see a marking on the pc
board labeled as "D16". just below this should be the matching diode, close to the bottom edge of the board. Remove this
diode and carefully re-assemble the radio(watch those faceplate pins!!

The radio will now TX 136-174 Mhz. As far as i know, you do not have to reset the memory to make the mod work( i have 70 out­of-band memories stored, all of them worked without resetting the unit!!!!!

September 5, 1998 - KC2AEI

Thanks to Chris KB3HPF for the pics.

Date: 03-02-2002
Subject: ic-2100h mod

So D-16 is the diode to cut, or the one that looks like it?
What is the number of the one you cut?

Date: 06-03-2002
Subject: ic-2100H mod

I just performed the mod and it worked like a charm. I would however, recommend only lifting one leg of the chip in case you
screwed up and did the wrong one.

User comment

User comment

From: Jason

From:

k1phs

This modification is read 4219 times.

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20-01-2001

(IC-2100) Expand receiver for IC-2100H EUR version

Expand receiver for Ver #02. #06 and #07. (EUR version]

By key funktion:

● Switch off the radio.

● Push the [LOW/DUP] and [MONI/ANM] , while turning on power.

By diode:

● Cut the D-16 on logic board. D-16 is located at centre, and below J2 and is the only NON-SMT diode.

After either mod, you will have:

136,000 - 174.000 MHz FM

(AM and 118 to 135,995 is NOT possible with the IC-2100H)

Date: 26-12-2001

User comment

From:

kg4qlr

Subject: modification
Thank you for the info it is greatly appreciated!!!!

This modification is read 2694 times.

19-07-1998

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(IC-211) IC-211 mod

SM5BSZ - Dynamic Range of 2 m Transceivers
Part 3: Modifications to the IC211 and IC245

Published in VHF communications Nr 2 1982.

The introduction to this series of articles was given in Edition 1/82 of VHF COMMUNICATIONS.
This explained in detail why the dynamic range of transmitters must be as great as possible, and explained this with the aid of
examples. A comparison of values measured on well-known commercial 2 m transceivers showed that there was a lot to be
desired in this respect. Part 2 of this series of articles, which was published in Edition 1/82,gave a number of modifications to the
TS 700.
In the TS 700 the problems were caused by undesired AM-modulation of the carrier. In ICOM IC211 and IC245, like in most
other transceivers, the noise is caused by undesired phase- or frequency-modulation.

The measured noise sidebands of a number of IC211 and IC245 transceivers are given in Figure 1. The continuous lines show the
measured values before modification, and the dashed lines afterwards.
Transceivers A and B were measured both before and after the described modifications. In the case of transceiver C, the VCO
was replaced by a high-quality (!), home-made oscillator.
The othertransceivers: D, E, F, and G were only measured before or after the modification.

Fig. 1: Sideband noise of various transceivers IC211/lC 245. Measuring bandwidth: 3 kHz.

The VCO of the transceiver series IC211 and IC245 exhibit the usual weakness of commercially available transceivers:
The varactor diode is fed via a 47 kiloohm resistor. The output of the phase comparator is low-impedance and has a relatively
low noise component.
However, a considerable noise voltage is present at the varactor diode, which is caused by the leakage current.
This voltage has a 1 /f component, which causes a correspondingly varying voltage drop across this resistor.

The easiest solution to this problem is to feed the varactor diode from a low-impedance source, which can be easily achieved. It
is only necessary to connect an RF-choke in parallel with the 47 kiloohm resistor.
After carrying out this modification, the noise sidebands will be considerably reduced, and the main component will now come
from the phase comparator.
In order to suppress this noise, it is necessary to build-up a passive filter as shown in Figure 2, and to insert it between phase
comparator and VCO.

Fig. 2: This filter should be installed between phase comparator and VCO

The filter shown has an output impedance of approximately 1 kiloohm at 10 kHz and will completely short out the noise caused
by the leakage current.
It will also suppress the noise from the phase comparator sufficiently to ensure that it will have no effect on the noise sidebands.

The filter causes an additional phase shift in the control circuit which can lead to instability and poor lock-in characteristics.
However, this phase shift can be compensated for by realigning the trimmer potentiometer in the active loop filter so that the
control circuit locks in correctly.
There are various different versions of the IC211 and IC245 transceivers and this potentiometer is to be found in different
positions in the unit.
In order to identify the correct potentiometer, one should study the circuit extract given in Figure 3.
It is designated R28 in this circuit, and often it is found that the best lock-in characteristics are obtained with this potentiometer
adjusted to one of its limit positions.
The active filter should be soldered with short connections directly to the VCO-module, as can be seen in Figure 4.

Fig. 3: The circuit extract from ICOM shows where the potentiometer is to be found that allows the phase shift to be adjusted.

Fig. 4: This photo shows where the parts should be located

The VCO of many transceivers will have been modified already by the manufacturer. This is in the form of a RC-network of 470
ohms / 1 nanofarad, which will have been inserted into the sourcecircuit of the oscillator transistor.
These two components are accommodated on the conductor side of the PC-board, after breaking the required conductor lane.
Figure 5 shows this ICOM-modification, as well as the modification recommended by the author, in the form of a circuit diagram.

This can be seen from the measured sidebands of transceivers A, B, and E in FigUre 1. ICOM probably wanted to redUce the
oscillator power with this modification in order to reduce the RF-voltage across the varactor diode.
This in turn will reduce the leakage current through the diode, and subsequently the voltage drop across the 47 kQ resistor.
After carrying out the recommended modifications listed in this article, the ICOM-modification will no longer be required, since
the voltage source of the varactor diode will exhibit such a low-impedance for lower frequencies that the 1 /f component of the
leakage current will not be able to cause any voltage drop.

Fig. 5: This partial diagram of the VCO shows both the ICOM modification, and the modification recommended by the author The
manufacturer's modification reduces the values of the noise sidebands by approximately 5 dB when compared with the original
state.

It should be noted that two components are somewhat critical:
The 10 microfarad capacitor should have a low leakage current, since such leakage currents can have a high noise component.
The author uses tantalum electrolytics. The RF-choke should be a good VHF-type, in other words, it should have a high Q so that
it does not deteriorate the Q of the resonant circuit.
The inductance and capacitance values are not critical, since any detuning of the oscillator resonant circuit can be compensated
for by correcting the core of L1.
A choke made from one layer of enamelled copper wire wound on a 1.5 mm diameter ferrite rod of 10 mm in length has been
found to be very suitable.

The author has taken such chokes from transistorized VHF/UHF TV-tuners. A coil wound from a quarter wavelength wire (thin)
would also be suitable.

A disadvantage of the recommended modifications should also be mentioned:
The lock-in time is increased for large frequency variations. This will be noticed as a short delay between transmit and receive
when operating split frequency operation (repeater operation).

This disadvantage can be avoided by connecting a pair of IN4148 diodes across the 33 kiloohm resistor (dashed lines in Figure

2).
The author has not tested such diodes in amateur transceivers, but in a different application where fast locking was required.
Such solution worked excellently. For these diodes to work, the output impedance of the phase comparator must be much
smaller then 33 k, which is the case for IC211 / IC245.
It is wise to connect an oscilloscope to the comparator output when all modifications are done. The AC component of the output
from the phase comparator should be below 0.5 V (peak), also when a considerable audio level is present at the built-in
loudspeaker, or knocking at the transceiver to simulate mobile usage.

The RF-choke should be constructed in a mechanically stable manner, since a microphonic effect will be caused if its hot end is
vibrated by a high pressure from the built-in loudspeaker, or during mobile operation.
The slow reaction of the phase control will then lead to an unreliable lock-in characteristic.
It is therefore advisable to glue the choke with an adhesive having good RF-characteristics (low tan delta).
The adhesive should be approximately 1 mm thick. It represents the dielectric of a stray capacitance, and if it is made too thin,
the high capacitance, and high electric field strength in the dielectric will cause losses and thus increased noise sidebands.

Several dozen IC211/245 were modified according to this description in Sweden and Finland.
According to my knowledge, no problems have been encountered. The average improvement at small frequency spacings from
the carrier is approximately 15 dB. This means that the described modifications reduce the interfering noise sidebands by the
same value as would be the case when switching off a 300 W linear amplifier and operating the station, "barefoot" with only 10
W !

In the case of the IC211, an improvement of approximately the same value will be present in the receive mode.
This improvement is less pronounced in the case of the IC245 due to its simpler input circuit of the receiver.

Part 4 of this series of articles will describe improvements to the FT 221 transceiver.

This modification is read 873 times.

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19-07-1998

(IC-22) Icom IC22S Packet Modification

The Icom IC22S is a ten watt diode matrix PLL synthesized 2 meter rig manufactured in the early 1970's. In it's stock condition it
tunes 146-148 MHz in 15 KHz steps. Since I am sure there are a few of these sitting on shelves collecting dust due to the limited
tuning range, why not modify them for the perfect packet rig.

First replace the 7.68 MHz Oscillator/Divider crystal (X1) with a 5.12 MHz crystal. This will move the band to 145.00- 146.94
MHz in 10 KHz increments. The repeater offset will now be 400 KHz which should not pose a problem in simplex packet
operation. I will give the diode matrix settings for the most commonly used packet frequencies. You can formulate others as
needed using the formula N=100*(f-145)+61 and the manual. The diode positions indicated ARE WHERE DIODES ARE PRESENT.
The other positions are left empty.

145.01= D5,D4,D3,D2,D1

145.03= D6

145.05= D6,D1

145.07= D6,D2

145.09= D6,D2,D1

This modification is read 719 times.

19-07-1998

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(IC-22) IC-22S mods for 5 KHz step

I have prepared information to modify the IC22S sythesizer to allow it to have 5 KHZ steps in lieu of the original 15 KHZ steps.
This will allow the rig to go onto 145.01 MHZ for packet radio operation.

In short, the modification requires changing a crystal, making some copper path cuts, adding some jumpers, and installing a new
divide by N counter which consists of three CMOS digital integrated circuits.

If you put it on a frequency as low as 145.01 you will also need to re-tune the front end and you may need to re-tune the VCO
free running frequency. I have made the mod to my radio and am using it to up-load this file. I re-tuned the front end to
increase sensitivity back to the normal although it did work without re-tuning. I did not have to adjust the VCO.

If you would like to receive the information which consists of a schematic of new counter, old and new block diagrams and
instructions to incorporate and test the modifications, send an SASE (standard business envelope, 22 cents postage) to:

Jon Reeves, WB9CNE

12125 Trolley Rd.

Oaklandon, In 46236-3056

NOTE:
The information which will be mailed is being prepared for publication.
It is requested that the information be used only for modification of your personal radio and not be passed on without this note
or placed on any bulletin board system. I am releasing the information now to assist packet radio operators in their efforts to
move to 145.01 MHz and would appreciate consideration of this request.

This modification is read 715 times.

19-07-1998

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(IC-22) Step modification (packet radio operation)

Before doing any other modification, pins 13 and 16 of IC1 (programmable divider, TC-5080P, PLL board) should be connected
together. This allows the PLL to accept all the binary codes and then cover all the frequency range possible with the 22S. This
modification is currently done and could be already done on your rig.

STEP MODIFICATION (PACKET RADIO OPERATION):

The normal STEP between "channels" is 15 KHz. For example, you can tune 146.610, 146.625, 146.640 MHz, but not 146.620,

146.630, etc...
The step is settled by the crystal X1 (on the PLL board), located near the VCO (big metal box). The normal frequency of this
crystal is 7.680 MHz. This crystal also sets the offset (normal: 600 KHz) when using duplex mode, since the offset is made by a
logic circuit that adds 40 to the binary code applied to the programmable divider (PLL). Think about it: 40 x 15 KHz = 600 KHz!!!

The step produced by a given crystal is calculated this way:
STEP = Xtal freq.(Hz) / 512
Example: Xtal 7.680 MHz: STEP = 7 680 000 Hz / 512 = 15 000 Hz = 15 KHz.
The offset is calculated this way:

OFFSET = STEP x 40
or: OFFSET = Xtal freq. / 12.8

Example: 15 KHz x 40 = 600 KHz

7.680 MHz / 12.8 = 600 KHz

If you want to have a 10 KHz STEP, you need to change the crystal X1 for a 5.120 MHz crystal:
STEP = 5.120 MHz / 512 = 10 KHz
Doing so will make the rig operate from 144.390 to 146.950 MHz, in 10 KHz segments. However, the OFFSET will be 400 KHz

instead of 600 KHz. Repeater operation is therefore impossible, but this modification is best for PACKET RADIO operation!
Suggestion: You can use a 10.240 MHz Crystal (which is common in CB rigs and electronic stores) and divide its frequency by 2

with a divider. You can use the unused pins of IC6 (uPD4013C) as a divider. To do this connect pins 9 and 12 together, enter
your 10.240 MHz signal on pin 11 and you get a 5.12 MHz square wave on pin 13.

If you want a 5 KHz step, You need a 2.560 MHz crystal.

This modification is read 669 times.

19-07-1998

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(IC-22) Band segment modification

The normal frequency coverage of the IC-22S (with X1=7.680 MHz) is 144.390 to 148.215 MHz, a range of 3.825 MHz (Fmax ­Fmin), by 15 KHz steps. The frequency segment covered by the IC-22S is settled by Crystal X2 (near X1 on PLL board). Its
normal frequency is: 44.563 333 MHz. The lowest frequency (Binary code 00) and the highest frequency (binary code 255)
covered by the radio with a given crystal (X2) is calculated this way:

Fmin. = (Xtal freq. x 3) + 10.7 MHz
Fmax. = (Xtal freq. x 3) + 10.7 MHz + (RANGE)

RANGE = (X1 / 2) - (X1 / 512)
Example:

Fmin=(44.563 333 MHz x3) + 10.7 MHz=144.390 MHz
Fmax=(44.563 333 MHz x3) + 10.7 MHz +((7.68 MHz/2)-(7.68 MHz/512))=148.215 MHz

As I said before, the normal coverage of the IC-22S is 144.390 to 148.215 MHz (With X1=7.680 MHz). The 215 KHz Higher than

148.000 are useless and limits coverage in the low portion of the 2 meter band. Changing X2 by a 44.488 333 MHz crystal will
make the IC-22S covering from 144.165 to 147.990 MHz (15 KHz steps).

Fmin = (44.488 333 x 3) + 10.7 = 144.165 MHz
Fmax = (44.488 333 x 3) + 10.7 + ((7.68/2)-(7.68/512)) = 147.990 MHz

An interesting modification is to change X1 for a 5.120 MHz crystal, allowing a 10 KHz step, and change X2 for two appropriate
crystal, each one allowing 2 MHz coverage.

With X1=5.120 MHz, replacing X2 by a 44.923 333 MHz crystal will give the following coverage:
Fmin = (44.923 333 x 3) + 10.7 = 145.470 MHz
Fmax = (44.923 333 x 3) + 10.7 + ((5.12/2)-(5.12/512)) = 148.020 MHz
With X1=5.120 MHz, replacing X2 by a 44.250 000 MHz crystal will give the following coverage:
Fmin = (44.250 000 x 3) + 10.7 = 143.450 MHz
Fmax = (44.250 000 x 3) + 10.7 + ((5.12/2)-(5.12/512)) = 146.000 MHz
These two crystals could be installed with a switching device, to use one at a time. This allows fuull coverage of the 2 meter

amateur band (144-148 MHz), in 10 KHz segments. Local oscillator can be slightly detuned to allow operation on 5 khz steps
(146.745 MHz, example). I have not worked on it yet.

This modification is read 739 times.

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19-07-1998

(IC-22) Recieve SSB and CW on IC-22S

Would you like to convert your IC-22S to receive SSB and CW signals? If you own a shortwave receiver, or a general-coverage
HF rig, you can do it easily, for less than a dollar!

All you need to do is to take a sample of the 455 KHz IF amplifier signal in your IC-22S and apply it to your shortwave receiver,
tuned on 455 KHz in USB, LSB or CW.

Connect a 68 K ohms resistor on the collector of Q6 (455 KHz IF amplifier).
It's a 455 KHz IF amplifier, NPN 2SC945; collector is the center pin. Connect the free end of this resistor on the inner conductor
of a coaxial cable.
Connect the shield of this coaxial cable on the ground (-) of the IC-22S.
The other end of this coax is connected on the antenna connector of your shortwave receiver, with the appropriate connector.
This coax could be RG-58U or shielded speaker wire; the length is according to your convenience. The resistor is used to limit
loading of the IF amplifier.

The frequency you want to listen is selected on the IC-22S. Your SW receiver must be tuned on 455 KHz. The mode you want to
use (USB, LSB, CW) is selected on your SW receiver. This modification can NOT be done in transmission, because too many
modifications of the IC-22S are involved. You would need to change the RF amplifier because it's in class C, which doesn't work
in AM and SSB.

R149 pot: adjusts low power. Reducing R148 increases maximum low power (less than 10 Watts...) possible with R149 pot.
R73 pot (30K): adjusts TX meter readout. When this pot is connected on D10 instead of D11, the meter indicates SWR. R73

could therefore be used to calibrate FORWARD reading.
R89 pot (100K): Adjusts SWR feedback, and therefore SWR protection level.
R132 pot: adjusts Mic. Gain.
R124 & R112 pots: Adjusts Maximun deviation.
R124 pot: Adjusts symmetry of clipping of mic. amplifier.

This modification is read 726 times.

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19-07-1998

(IC-22) Modifying the IC22A for 9600 baud operation

Author: Mike Curtis

by Mike Curtis, wd6ehr and Dave Shalita, w6mik

This is one of the more difficult rigs to modify - most are even simpler!
This mod will make your IC22A into a dedicated 9600 baud packet radio. Components with * are added to the crystal board.
Remove the trimmer capacitor for the transmit crystal socket you'll be using for 9600 baud. Replace with the above circuit. The 4-

20 pF trimcap should be a good quality ceramic or other low-drift trimmer. (Sorry - Radio Shack doesn't have anything suitable.)
Connect 2 10K resistors to C-53 (both sides) and tie the other ends together. This junction is where you'll pick off your RXA.
Turn R-67 (dev control next to P-1 and P-2) completely counterclockwise. This kills signals that may get into the phase

modulator.
Using a service monitor, or oscilloscope connected to the detector of a receiver, adjust the varactor bias for the best eye pattern.
Alternate bias adjustment:
Use the k9ng's 4800 Hz "idle" tone to adjust your modulator for best linearity. Using a service monitor, or a receiver with a fairly

wide passband, adjust varactor bias for the "best" sine wave. Thanks to Brian Kantor wb6cyt for this tip.

This modification is read 685 times.

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19-07-1998

(IC-228) IC-228 mods

I have the mod info from ICOM. It is best to have the diagram in front of you when performing the mod, but for the bold ones,
here goes:

There are three PC boards in the rig. The TX and RX boards are on the top and bottom of the rig. The logic board is behind the
front panel, and the LCD display and front panel switches are mounted on it. It is the logic board which will be the object of your
surgery.

1. Remove D-19

2. Install D-7 - (Type 1SS193)
D 7 should have three terminals, but only one is used.
It looks something like this:

| C

----------­ | / |
| / |

----------­ A| |

There is no connection to the terminal on the lower right. The Cathode of a 1N914 diode Can be connected to the upper terminal,
and the Anode to the lower left. (as indicated by the C and A.

In locating the positions of D-19 and D-7, reference the lithium battery.
D-19 is at the 1 O'clock position near the edge of the board, and D-7 is at 2 O'Clock and adjacent to the battery.

Date: 25-08-1999

User comment

From:

webmaster

Subject: What did this modification.?
Please mail me if you know what this modification do.?

Best regards
Erik Hansen - OZ2AEP
webmaster
www.mods.dk

This modification is read 705 times.

19-07-1998

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(IC-229) IC-229H, and AM aviation band modification

Eons ago, I asked:

> Does anyone know what is required to make an Icom IC-229A (or IC-229H)
> receive in the aviation band (118-136 MHz or so)?
>
> For an IC-2SAT handheld, it's just a three-button-down-during-power-up
> sequence, and it does AM demodulation in that subband. Is it so simple
> with the IC-229A/H? I called the Icom info line, but they were far from
> helpful. Eventually said "yes, it does do AM demodulation in that band",
> but were very reluctant to admit that and flat out said no way they'd tell

> you how to do it. Sounded like CYA paranoia regarding type acceptance....

Quick summary:

● Yes, it does do AM demodulation. Many people are unhappy with its performance, but I was impressed. Variation in radios,

or variation in tastes, who knows....

● Yes, it requires a hardware mod. No, the procedure described in "CQ" magazine is not exactly right. Yes, it is easy to do.

● It has a wide bandwidth and is sensitive. Therefore, you may have intermod problems.

More detailed:
In the true spirit of the net, I got several responses that were just noise. Along the lines of "No, I know nothing about that radio,

but a buddy of mine got a different one once, I think maybe it was a Yaesu, but I'm not certain. It might have done AM
demodulation. Or then again maybe it didn't, now that I think about it. Well, I guess I don't know. Hope this is a big help to
you!!" Duh.

However, several were helpful, and the more useful ones are excerpted below. There was a review of the radio in "CQ" this past
year (don't have the exact date in front of me). The following change/additions need to be made to the text where it describes
how to enable aviation-band AM receive:

1. To disassemble the radio,

2. When removing the top and bottom case halves, be careful, as the speaker is connected to one!

3. Remove the three knobs by gently pulling them straight out from the panel.

4. With a spanner (or needle-nose pliers) remove the nut mounting the front panel to the microphone connector.

5. Now remove the screws holding the front panel (black plastic) to the frame, and remove that panel.

6. You will now find that there is a subassembly with a "backbone" of 0.25" machined plexiglass, held to the frame with three
machine screws. Remove those screws and gently swing that subassembly away from the frame. You now have access to
the diode that must be clipped.

Otherwise, things are done as the review says. The CQ review gave a good report of its AM aviation band performance. I would
agree with that, and suspect that at least some of the complaints were due to the original signal -- there's a ton of background
noise in a private plane. However, airliners should sound quite clear. Sensitivity, even that far away from the ham band, seems
good. Airliners at altitude up to 50-100 miles away can be heard, even with just a J-pole antenna near ground level. (assuming
you're not at the bottom of a steep valley, of course!) Sensitivity in other non-ham bands seems good as well, it has no trouble
picking up sheriff's dispatchers maybe 45 miles away.

Too much sensitivity and too much bandwidth may cause big problems with intermodulation, if you're in an RF-rich environment.
I have no idea how it would perform in, say, downtown Chicago, but I suspect you'd hear all sorts of intermod and images. There
were a couple of odd images I noticed, but nothing distractingly bad. The built-in attenuator might help.

My father is now using one, with a J-pole at 53' and an 11-element beam at 48', from relatively high ground in a rural, hilly area.
It seems to do very well for such an application, as it gives you three radios (ham, aviation, public-service scanner) in one box.
45-50W output means you can hit what you can hear, and it's sensitive enough to hear quite a bit (some some repeaters out to
100 miles are useful). At least two NOAA weather broadcasters around 162 MHz are audible.

Oh yeah, when you rotate the knob in "VFO" mode to tune up from 174 MHz, it skips to the range 340-380, and then to 870­890, before wrapping around to 118 again. Don't get excited, it doesn't receive in 340-380 or 870-890, as the VCO won't lock up
there. It does AM demod 118-134 and FM 134-174 MHz.

On to the excerpts.... For the following, only the pad pair marked as "D5" had a diode in my dad's:

> From: [e-mail] (Dugal James P.)
> Date: Tue, 10 Dec 91 13:12:42 -0600
> To: [e-mail]
> Subject: Re: IC-229A/H AM aviation band mod
> Newsgroups: rec.radio.amateur.misc
> Organization: Univ. of Southwestern La., Lafayette
>
> I retrieved this from my "archive" -- hope it helps!
> --James N5KNX
>
> Here's some info on the IC229A/H, (indirectly) from ICOM:
>
> The stock radio has RX: 136 - 174, TX: 140-150, FM only.
>
> When diode D5 (conventional, upright diode on the logic board)
> is cut, 118 - 135.995 MHz can be received in AM mode.
> [Local reports indicate the audio is acceptable but not as good as,
> for example, AM received on a PRO-2004 scanner]
>
> To expand TX to 136 - 174 MHz, locate chip diode D9. Ascertain that
> the vertical pair of pads to the right are OPEN. Short the next pair
> of vertical pads to the right [with solder, perhaps].
>
> These changes pertain only to the USA model.
>
> Here's some ASCII art to clearify:

> _________________________________________________________
> R5 R4 |
> R1 |

> R2 . .
> D1 D2

> -----------+ .. ..

> | -D3­> | -D4­> IC4 | -D5­> -----------+ -D6­> -D7- . .. _ _
> D8 D9 _ _
> O .. .
> C7
> X1 |
> ________________________________________________________|

As far as the following two, I got the impression that the IC-229H did as well at aviation band receive as my IC-2SAT.... One

thought -- since the "CQ" review described as slightly different physical construction, I wonder if there have been some slight
changes during the production run leading to improvements in AM demod performance??

This modification is read 1101 times.

19-07-1998

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(IC-229) IC-229H & 9600 bauds (Anglais)

After trying to solve this the easy way with no luck, by looking for docs already posted, a few of us have decided to bug this out.
A quick call to ICOM put us on the rite track. This non-destructive mod for the IC229h works well for 9600 baud packet. You will
need your schematic that came with your radio. However, our call to ICOM revealed some discrepancies on the schematic in the
FM detector stage, primarily the FM detector chip itself.
Earlier models had the TOKO TK10487M detector and the newer models have the MOTOROLA MC3372M. ICOM, unfortunately,
did not make this change in the schematic supplied with the radio. This document will show the connection points for both chips.
Remember to use good quality shielded cable like RG-174u, RG-178u or similar. Most of the points are going to require micro­surgery, so get out your pencil point soldering irons and magnifying glasses.

1. TXA:
On the schematic you will see a block labeled "VCO UNIT". At the bottom of this there is a four pin connector. The third pin

is labeled "MOD".
This is where you want to inject the TXA from the modem. The "VCO UNIT" in the radio is shielded by a can. Removing this
"CAN" to get to the circuits can be a tedious endeavor. So you can find this "MOD" point on the underside of the radio. It is
located beneath a flat metal shield about 1" X 2". After removing this, with the front of the radio towards you, the point can
be found in the right corner towards the front where the shield covered. There will be four solder lands rite in a row from
left to right. Trace these lands with the schematic to find the "MOD" land. Solder your TXA there. Replace the metal shield.
This is as tuff as it gets. I promise!

2. RXA:
Well this one is easier. If your radio has the TK10487M, solder RXA to pin 11 of this chip. If your radio has the MC3372M,

solder RXA to pin 9 of this chip. Either chip can be found on a board in front of the "metal VFO shield can", on the top side
of the radio. You may have to tilt the board a little, but be careful. Don't apply too much heat to the chip or you will have a
big problem. I followed the trace away from the chip and attached RXA.

3. PTT:
This can be found on the mike jack pin 5. I made this an internal connection for neatness. Neatness counts!

4. GND:
If I need to tell you where to find ground, you shouldn't be doing this mod yourself. Attach all the shields from the above

wires together outside of the radio to modem ground. Attach only one shield internal to the radio, the "CAN" is a good spot.
You don't want to cause any ground loops, do you? Protect the other two shields from shorting to anything in the radio.
This is why they make heat shrink tubing.

You may have to add 5-10mF non-polarized capacitors in series with the TXA and RXA lines. Some modems have included these
in their circuit, so check. Now you are ready to make the connections to the modem. This will have to be left up to you. There
are too many modems and tnc's out there to list all of the connections to them. But you should have the docs with your modem,
so it should be easy. Disconnect the radio from the modem if you use the radio for anything else. Well there you have it. This
works great, it is what I am presently using.

This modification is read 859 times.

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19-07-1998

(IC-229) IC-229H Fix CPU/Display board

Hello From Mike, N3KCT !
For those owners that have encountered CPU RFI from your IC-229, Here's the fix!
The problem is cured by properly grounding the CPU/Display board.
First remove the top and bottom covers. Then carefully remove the threaded mic connector which fastens the mic jack to the

front panel.
Remove All Knobs and then the four screws that hold the front panel onto the metal chassis. This exposes the clear display

housing and CPU board when you slide the front panel off.
There will be three screws that hold the display panel along with the CPU board onto the main chassis. Two are next to the mic

connector, and one is next to the channel control knob. Remove these three screws and the entire display/CPU section will come
off in one piece. You will not have to disconnect any of the wiring.

Carefully clean the ground traces that these screws go through on the back of the CPU board and tin them. They are around
each screw hole on the CPU board. When the radio is re-assembled, these traces will now properly ground out the CPU section
and cure your RFI problem.

Appearantly something happened during manufacture that caused these to be covered with that "clearcoat" stuff to prevent
them from grounding out.

This fix has been 100% effective on mine and several other radios.
The problem is NOT in the mic, it is just poor grounding of the CPU!
Any questions or comments can be sent to:

N3KCT@NR3U.#NCPA.PA.USA.NA

73 de Mike !!

P.S.
I do not assume any responsibility for this mod, so procede only at your own risk and capability.

This modification is read 917 times.

19-01-2002

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(IC-2320) Extended RX/TX

Author: Marcelo - ZZ2MWL - [e-mail]

Hello radio partner's,

Here I expose what got working in the IC2320.

1. Open the radio and remove the front

2. In her meets the logical plate and it is in her that we will work

3. Remove the diodes marked as D9 and soon below him you will see 3 small diodes, remove only the diode of center marked
with "x", doesn't remove other diodes, because in spite of him to be very similar at the IC229 doesn't forget that this is
DUAL

With this you will have an opening of:
RX: 118-174 VHF
TX: 140-150 VHF
RX: 300-399 UHF
RX: 430-440 UHF
TX: 430-440 UHF
RX: 800-950 UHF

Is not necessary reset the radio!!!

_________________________________________________________
R5 R4 |
R1 |
R2 . .
D1 D2

-----------+ .. ..

| -D3­ | -D4­ IC4 | -D5-

-----------+ -D6-

-D7- . .. _ _
D8 D9 _ _
O .. .
C7 ?x?
X1 |
________________________________________________________|

So long, 73 from Brazil

Marcelo Medrado
ZZ2MWL

This modification is read 260 times.

19-07-1998

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(IC-2330) IC2330A expanded range

I picked up a IC-2330a and found there were no mods..at least i couldn't find any, so i decided to find them myself! and this is
what i found...

I have had no problems since performing these mods, but of course i claim no responsibility if you trash your radio, and of
course it will void your warranty!

OK here we go..
on the logic board (behind the display board) are two diodes D5, and D6...

cut D5 to get 215.00 to 230.00 Mhz TX/RX
cut D6 to get 118.0 - 135.0 AM/RX

There is a solder pad on the back of the logic board which when the pads are connected together will enable 136-174 TX/RX, but
disable the tone encoder on 2meters only...
haven't spent much time on that to figure out why or how to fix that so i left then unconnected (don't need to xmit there
anyway) but if someone else can figure it out let me know! i love all mods so if anyone has any more they know of for this radio
pass them along to me as well..
Good luck and thanks for reading!! Steve KD6QPQ

This modification is read 628 times.

28-05-2000

(IC-2330) IC-2330A expanded range (another way)

Author: Takeshi Kudoh - [e-mail]

I found another way of modification for IC-2330. After the modification, we can receive;

118.000-135.995MHz AM(RX)

136.000-174.000MHz FM(RX)

144.000-146.000MHz FM(TRX)

320.000-479.000MHz FM(RX)

430.000-440.000MHz FM(TRX)

830.000-950.000MHz FM(RX)

This way might be more difficult than yours, but it is easy.

First, a switching diode should be put on the circuit board in the circle on this picture.
Second, the transceiver should be reset. To be reset, turn it on with pushing [SET]+[MW].
And turn off and turn it on again with [V/M]+[SET]+[DN]. [DN] key is located on microphone.
That's all of modifications for IC-2330.

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In addition, if you want to put an external antenna for 830-950MHz, put coaxial cable in the circle on this picture.

This mods is shown in a web page in Japan. That means it wouldn't work well coz this mod is for IC-2330 sold in Japan.

Please try to do it and let me know the result.

Regards//Takeshi Kudoh

[e-mail]

This modification is read 604 times.

19-07-1998

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(IC-2340) IC2340H att modification

From: [e-mail] (Pinchook Ronen)

This text deals with ICOM's Mobile radio IC2340H. On some of icom dual band mobile transceivers there is an RF attenuator
which attenuates the received signal by 20dB. In my opinion this is a great feature especially when you operate in cities or in
area's with lot of RF signals, repeater, etc.

The attenuator function reduce the intermodulations that appears while receiving in those areas, and let you listen more quietly
on your favorite channel, when you listen to a local repeater you can hardly feel the 20dB attenuator, but the intermodulations
almost disappear.

The problem is that the attenuator was featured on old icom mobile rigs (such as IC2340H, IC3230H), but not on the IC2340H.
The next lines will guide you how to add this feature. All you need is 2 1p2t small switch, and 2 12Kohms resistors.

VHF MODIFICATION

1. Open the upper cover of the transceiver.

2. Locate D9 on the print (left to the Power Amplifier while looking from the front of the transceiver)

3. Solder a 12K resistor to the anode of D9 as close as possible to the diode, (with no wire, the pin of the resistor should be
soldered to the pin of the diode)

4. The other side of the resistor should be wired to the small switch (the switch can be mounted on the back of the
transceiver, there's an hole in the heatsink which you can use to insert the wires to the transceiver.

5. The other side of the switch should be tied to 5V (you can find a 5V terminal at J2 pin 2, j2 & j1 located near the VCO at the
front of the print it is a 2*4pin sip connector, j2 is closer to the VCO.

UHF MODIFICATION

1. Open the lower cover of the transceiver.

2. Locate D17 on the board (this diode is wired under the board, just beside L22. there are 2 holes, I am talking about the one
located closer to the antenna)

3. Solder another 12K resistor in the same way it was done in the vhf to the anode of D17 just under the print ( the anode is
the left pin of the diode ,the pin which located closer to the power amplifier.

4. The other side of the resistor should be wired to the other small switch...

5. The other side of the switch should be tied to 5V (for example to the right pin of the regulator IC7)

Explanation
When you turn this switch on, it turns the diodes on, and attenuates the received signal.

This modification was tested, but you will do it on your own risk.

This modification is read 756 times.

20-01-2001

(IC-2340) Some mods for the IC-2340H

The diodes D12 to D20 and D10 + D8 on the logic board is the diodes that control frequencyrange and model version.

[Logic board]

-----------------------------------------------------------------------------------+

------ |
W1 |
|
|
J 7 D14 D15 D12 D13 |
+-------------------------------+ +----+ +----+ +----+ +----+ |
| | | | | | | | | | |
| | +----+ +----+ +----+ +----+ |
+-------------------------------+ |
+-----+ +----+ +----+ +----+ |
| | | | | | | | |
+-----+ +----+ +----+ +----+ |
D18 D19 D16 D17 |
|
+---------+ +--------+ |
| | | | |
+---------+ +--------+ |
D10 D8 |

-----------------------------------------------------------------------------------+

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Minirepeater:

● Remove D16 on logic board. (Not necessary on USA version)

● Set the desired QRG on each band.

● Push the [VHF MAIN] + [UHF MAIN] VFO knob and push [SET] at the same time.

The memory channel indication changes to "L" (L=Minirepeater mode)

To return to normal, push and hold [SET].

Expand RX for the EUR version:

By key funktion:

● Switch off the radio.

● Push the [V/MHz] (for VHF), and [SET] and [DN] on microphone at the same time, while turning on power.

By diode:

● Remove D17 diode on the logic board.

● Do a full reset by switching off the radio. Then while pushing [SET] + [SPCH], turn on the radio.

After either mod, you will have:

118,000 - 135,995 MHz AM
136,000 - 174,000 MHz FM
320,000 - 479,000 MHz FM
830,000 - 950,000 MHz FM (Needs extra coaxial cable to receive anything)

Expand RX for the USA version:

● Cut W1 jumper wire on logic board.

After mod, you will have:

118,000 - 135,995 MHz AM
136,000 - 174,000 MHz FM
320,000 - 479,000 MHz FM

This modification is read 766 times.

20-01-2001

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(IC-2340) IC-2340 mods

Symptom:

Any of the following: Cannot change band to UHF, no UHF volume or squelch control, no UHF tuning, or strange-sounding beep
tone.

Cure:

Rework bad soldering at J3 on display unit and replace the SW-B board with a factory-modified flex PC board.

Symptom:

No audio output from receiver.

Cure:

Remove excessive solder on the Main-A unit near the audio amp.

Symptom:

Howling if volume is turned up when using UHF.

Probable Cause:

Microphonics in VCO section. Resolder the ground spring at the UHF VCO shield. You may also add a second spring for further
improved resistance to microphones.

This modification is read 748 times.

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19-07-1998

(IC-2350) IC-2350 expand RX/TX and Crossband rep

25 Nov 1995

On logic board behind the front panel

1. Remove D9 to expand vhf rx

2. Remove d10 to expand uhf rx

3. Cut w1 jumper wire to expand tx on all bands

4. AM selectable by holding [V/MHZ] button for 2 secs

5. Crossband repeat, set desired freqs press [VHF MAIN] [UHF MAIN]and [SET] simultaniously.To deactivate press [SET] for 2
secs

There is also a remote access feature but its lengthy and I hate typing. Larry G4OXY

This modification is read 849 times.

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19-07-1998

(IC-24) Frequency expansion for IC24

1. Remove, if present (S/N < #3000 ??), D13 on the LOGIC UNIT.

2. Reset the CPU ( [func] + [a] and "power on" ).
The frequncy-range of the logic unit* is now :
75 - 195 MHz
200 - 490 MHz
740 - 960 MHz
* Because some particular sets have VCO's that won't "lock" over the total range, the frequency-range that is really
covered by the transceiver can be smaller as the mentioned ranges.

->Verry Interresting: in the "AIR-band" the receiver even switches to AM-mode !! (108 - 138 MHz).

For those who want more.....

1. Remove diode D8 (logic board);

2. Place, if not present yet, D7;

3. Place D12;

4. Remove D13;

5. Push, at the same time, [light],[B], and [#], while turning on the power (probably you need three hands for this), The
transceiver now executes a "display-test".
Release the buttons only when the display-test is ended.
The frequency-range of the logic unit* is now:
VHF: 0 - 355 MHz
UHF: 355 - 1310 MHz

This modification is read 972 times.

19-07-1998

(IC-24) Cross-band repeater operation IC-2

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1. Remove diode D14 (if there is anyhow & anywhere still one diode left on the logic board);

2. Select the desired frequency in the VHF range;

3. Select the desired frequency in the UHF range;

4. Switch the transceiver in "SPLIT"-mode ([func] + [c]);

5. Switch on the CROSS-BAND-REPEATER mode by pressing [func] + [5] + [d].

-> Switching off the REPEATER-mode?: [func] + [d]!

This modification is read 790 times.

19-07-1998

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(IC-24) Out of band modification of the ICOM IC-24AT

The Icom IC-24AT is truly a remarkable unit. Having it's genesis in the IC-R1, Icom's extremely wide band Hand Held Receiver, it
is capable of receiving a wide range of frequencies, as well as being able to transmit on short excursions, outside of the amateur
two meter and 440 MHZ. bands.

The more current models can be modified to receive out of band, by a simple software (not necessary to physically open the
transceiver) procedure as follows;

Turn the power switch off. While simultaneously holding the "light" button, the "B" button, and the "#" button, turn the radio on.
All elements of the display will light up.
Continue holding the buttons until the display goes out. It may be helpful to have a buddy give you an extra hand during this

procedure....Your unit will now receive out of band.

The older models of this transceiver, require the removal of diode D13, before performing the above procedure. D13 is on the
main logic board and is a discreet diode near the center of the board. It is the diode on the left of the two on the board when the
radio is open and held with the controls away from you.

The "stock" transceiver, was also not designed, to provide full direct keyboard entry of the operating frequency. This can also be
modified by one or both of the two procedures below;

To directly key in the 10Mhz. frequency, simultaneously hold the "light" button and the "2" button, while turning the radio on.
To directly key in the 100Mhz. frequency, simultaneously hold the "light" button and the "3" button, while turning the radio on.
The modification of the unit to enable it to transmit out of the amateur bands is a fairly simple procedure. It is however,

complicated by the fact that the construction technique used in this transceiver is "Surface Mounted Technology." If you have no
experience dealing with this technology, you may well be better advised to defer this procedure to someone who has. It is
extremely small and delicate, and is best done with specialized equipment. Also, because the unit may not be FCC type accepted
for all the frequencies on which it can then transmit, it may not be legal for you to use it, despite the fact you may be licensed to
transmit on those frequencies. This information is provided only for those who are licensed for and want to use the unit on MARS
and CAP frequencies, where there are no type acceptance restrictions. The procedure is as follows;

● Order a couple of DA204u diodes from Icom or your Icom dealer. These are a special three terminal device with two diode

in one package. They are very very small, about half the size of one of the key buttons on the touch tone pad.

● Locate and remove the diode device in position D8

● Locate the vacant position of diode D7 and attach one of the DA204u diodes at that location.

● Locate the vacant position of diode D12 and attach the other DA204u diode at that position.

● If diode D13 (procedure above) has not been removed, remove it.

The unit will now transmit out of the amateur bands.
The above modifications provided the following capabilities with my particular unit.

FREQUENCY COVERAGE

(VHF)
RECEIVE TRANSMIT

74.9 Mhz. - 127.9 Mhz. OFF

138.0 Mhz. - 168.0 MHz. 138.0 Mhz. - 159.0 Mhz.

174.1 Mhz. - 189.69 Mhz. OFF

200.0 Mhz. - 287.22 Mhz. OFF

310.0 Mhz. - 349.0 Mhz. OFF
(UHF)

355.0 Mhz. - 409.98 Mhz. OFF

412.37 Mhz. - 498.0 Mhz. 410.5 Mhz. - 470.0 Mhz.

792.85 Mhz. - 966.66 Mhz. OFF

Receive sensitivity throughout both of the Ham bands was better than .5 of a microvolt. Sensitivity in the 200 Mhz. range was a
disappointing 1 millivolt and in the 800 Mhz. band a good .7 of a microvolt. Remember, while the unit will receive on those
frequencies, it is illegal to monitor cellular telephone communications.

This modification is read 1011 times.

19-07-1998

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(IC-24) IC-24AT ext frquency

I received the following mods for 24AT out-of-band from a very reliable source (although they don't specify RX only or RX/TX),
for 75-195 MHz, 200-490 MHz, and 740-960 MHz. Rumor has it (unconfirmed) that the unit even switches to AM in the air band!

1. Remove diode D8 [see figure below]

2. Attach diode D7 [I believe this is already equipped]

3. Attach diode D12

4. Remove diode D13

5. Simultaneously hold "LIGHT", "B", and "#" keys and turn the power on. Release all keys after the display goes out (checks
all LCD segments). [This is supposed to enable the out-of-band frequencies above]

6. Simultaneously hold "LIGHT" and "2" keys and turn the power on. This enables the 10 MHz frequency digit entry.

7. Simultaneously hold "LIGHT" and "3" keys and turn the power on. This enables the 100 MHz frequency digit entry.

__________________
| |
| |
| |
| CPU |
| |
| |
| |
|________________|

o o o D7 lower left pin is
[D7] [D8] anode of one diode,
o o o lower right is cathode
of the other. Top pin
o o is common
[D12]
o D12 upper pins are cath­ odes of diodes, lower
is common anode.

__I_ __I_ See text
| | | |
D13 |__| | | D?
|/| | |
| | | |
|__| |__|
I I

WARNING: I have NOT tried the hardware mods and cannot vouch for them, so proceed at your own risk!
I am told that the newer 24AT's (believed not to have made it to the US yet) will have the hardware mods in place, so only steps

5-7 will be necessary. So, try this first. Steps 5-7 don't seem to have any effect on a 24AT without the correct hardware mods.
BTW, this has been attempted on 2 units with serial numbers around 1000 and mid-1100's, neither of which worked. :-( Like I
said, the ones with the mods aren't here yet.

There are 5 screws to remove the case (5th is on the strap hook). Keep the top panel controls with the front of the radio, and be
VERY careful pulling the back off because there are fine ribbon cables connecting the front & back. I don't think they'll take much
flexing.

Additionally, diodes D7, D8, and D12 are surface mount components. They contain 2 diodes connected to 3 pins. Diodes D7 and
D12 are different configurations. I believe D8 and D12 are different, so I wouldn't put the removed D8 in the spot for D12. Since
they are surface mount, removal of D8 may not be all that difficult for those with steady hands and a fine low power soldering
iron, but adding D12 would be a bear. I know of no reason that small discrete diodes couldn't be used in for D12. D13 is a small
but standard axial diode, and can be easily cut.

It is for this reason I have not attempted the hardware mods. Now, if the referenced posting is correct, and only D13 needs to be

cut... I'm guessing, but it could be that the rest of the diode changes are for the 10 MHz & 100 MHz digit entry (which I'd like but
could live without) or out-of-band TX, or the like.

If anyone has tried only cutting D13 and resetting? Did it work? What is your serial number? Please post to the net!
Mike Pflueger

Packet: WD8KPZ @ W1FJI
Transmit range doesn't appear to be affected unfortunately. I was at least hoping for 420-450 coverage. BTW, I tried each

amateur band from 6m to 23cm. The PLL doesn't lock up at either end. Another negative is the frequency step on 220 doesn't
allow one to hit each possible repeater slot.

73 de Gene WA1UXA

This modification is read 871 times.

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19-07-1998

(IC-24) IC-24AT Keyboard command summary

This is an attempt to document all of the known key sequences for the ICO IC24AT (144/440MHz dual band hand held). Some
key sequences may be common with the IC[2,3,4]SAT, therefore a fewkey seqences fr thoseradios re also on this list. Some ke
sequenes requre optins (such as the PL encode/decode board).

This is not designed to replace the owners manual, but to summarize the information in one place.
Note: Many controls vary depending on the current mode, i.e.: Scan up/down will search frequencies when in VFO mode, and

will scan meory channels when in Memory mode. Consult the owners guide for complete iformation.

KEY/COMBINATION = Result, action

---------------- -------------------------------------------------------------

0-9,A,B,C,D,#,* = note: when transmitting these will generate DTMF tones
0-9 = Enter frequency (can also use the VFO knob)
A = VFO mode / clear incomplete entry
B = Memory mode
C = VHF / UHF change
D = Call channel
* = Step frequency down/scan down
# = Step frequency up/scan up
MONI = Open squelch and change to input frequency (if not simplex)
while button is depressed
H/L/DTMF = Select High/Low power, or (while transmitting) send
preprogrammed DTMF codes
FUNC + 0 = Dial set
FUNC + 1 = PL enable (when option is installed)
FUNC + 2 = Code squelch [NOT for the IC24AT, IC[2,3,4]SAT option only]
FUNC + 3 = Skip memory
FUNC + 4 = Duplexoperatin
FUNC + 5 = Code [NOT for the IC24AT, IC[2,3,4]SAT option only]
FUNC + 6 = Mask freuency
FUNC + 7 = Priority mode on/off (operation dependent on current mode)
FUNC + 8 = Set mode (several different functions, press A to exit)
FUNC + 9 = Real time clock and timer functions (press PTT to exit)
FUNC + A = Memory to VFO transfer
FUNC + B = Memory Write
FUNC + C = Split operation (cross band full duplex)
FUNC + D = Lock mode / Cross Band Repeat disable
FUNC + * = Scan programmed limits (down)
FUNC + # = Scan programmed limits (up)
FUNC + 5 + D = Cross Band Repeat enable (split mode must be on!)
Diode D14 (right diode on CPU board) must be removed to
enable the use of this function)
FUNC + MONI = RX/TX light enable / disable
FUNC + H/L/DTMF = Select DTMF Autodialer memory
Func + VFO knob = Change frequency/memory channel
(according to dial set, see FUNC+0)
Func + LIGHT = Lock light on (don't time out)

H/L/DTMF + VFO knob = Change output power (4 power levels when using 13.8 vdc)

The following key combinations selects "power on modes". Start with the radio OFF, then hold down the indicated keys, and
continue to hold them while turning the power ON. Some 'modes' override others.

LIGHT + * = PTT enable
LIGHT + 0 = PTT Disabled (inhibits the transmitter, good security method)

LIGHT + 1 = 1 MHz digit set (4 digit frequency entry)
LIGHT + 2 = 10 MHz digit set (5 digit frequency entry)
LIGHT + 3 = 100 MHz digit set (6 digit frequency entry)
LIGHT + 4 = Scan pause until signal disappears
LIGHT + 5 = Scan pause for 10 seconds
LIGHT + 6 = ???? Unknown action
LIGHT + 7 = Power Save deactivated (use this for packet operation)
LIGHT + 8 = Power Save (minimum - 0.125 / 0.5 second)
LIGHT + 9 = Power Save (maximum - 0.125 / 2.0 seconds)
LIGHT + A = ???? Unknown action
LIGHT + B = ???? Unknown action
LIGHT + C = ???? Unknown action
LIGHT + D = ???? Unknown action
LIGHT + # = ???? Unknown action
LIGHT + B + # = RX Extended Range enable
This requires that diode D13 is removed (left diode on
CPU board). Note that this diode has already been removed
by ICOM at the factory on many units. Be sure to hold
these keys down until the activity display stops and is
showing a receive frequency.

FUNC + A = Reset the CPU (this will clear all the memory channels to the
factory defaults)

This modification is read 820 times.

19-07-1998

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(IC-24) IC-24AT sensitivity

Following the frequency expansion modification (as specified by Icom), a sample IC-24 was recently tested for tuning range and
input sensitivity for an S9 signal. While the sensitivity measurements should not be directly compared with the manufacturer's
specifications (usually measured reference to a signal-to-noise quieting ratio), this "quick and dirty" data should give you a good
idea of the sensitivity to a medium-strength signal.

Tuning Range Mode Band Sensitivity for S9 Signal

74 - 107.995 MHz (fm) VHF range approx 1 mV
108 - 136 MHz (am) VHF range 10 - 30 µV
138 - 240 MHz (fm) VHF range 1 µV - 1 mV (1)
250 - 302 MHz (am) VHF range 50 µV - 1 mV (2)
310 - 354.995 MHz (fm) VHF range 50 µV - 3 uV (2)

355 - 409 MHz (fm) UHF range 3 - 10 µV
417 - 490 MHz (fm) UHF range 1 µV - 100 µV (3)
805 - 955 MHz (fm) UHF range 10 - 100 µV

Notes:
(1) The sensitivity from 138 - 150 MHz was 1 uV. From 150 - 240, the sensitivity decreased almost linearly from 1 uV to 1 mV

(with input voltage plotted logarithmically).
(2) The sensitivity increased almost linearly for both these ranges (with input voltage plotted logarithmically).
(3) The sensitivity plot looked like a "U" with the bottom of the "U" corresponding to the range 440 - 450 MHz (1 uV). The

sensitivity then got worse below 440 and above 450.
(Tests courtesy of WB6GTM)

This modification is read 792 times.

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19-07-1998

(IC-24) IC-24AT enabling the burst-tone

I have the ICOM-Dualband-Handy IC24AT (Asia Version) and want to modify it to enable the 1750 Hz-tone for repeater­operation.
I searched all the PR-Mailboxes in HB9 for mods but i found nothing about enabling the burst-tone.
The Printed-Circuit-Board look like this:

+---------+
I I
I I
I micro I
I Contr. I
I I
I I
+---------+

* * * *
D5d d6d
* *

* * *
dd7 d8D
* * *

* * * *
d11 dd12
* *

o o

d13 d14

o o

In my Handy, only D5 and D6 are mounted. I measured the pins with a multimeter and found following:

-D5 is a pair of diodes were the under, center pin is the cathode of both and the upper two pins are the anodes

-D6 is only one diode where the upper left pin is the anode and the lower, center pin is the cathode. The upper right pin of D6 is
not used.

So, all I need is the info which diodes are to remove or attach and is there still more to do (like adding some resistors)?
vy 73 de HB9IQW @ HB9OS

This modification is read 766 times.

19-07-1998

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(IC-24) IC-24 auf 9600 Baud

Umbauanleitung für das Handfunkgerät IC24 auf Packet-Betrieb mit 9600Bd
Sicher sind viele Om's noch im Besitz eines Icom-Handfungerätes IC24. Obwohl das Gerät schon älter ist, habe ich nirgends eine

Umbauanleitung für 9k6 ge- funden. Anscheinend hat sich bisher niemand die Mühe gemacht, dieses Gerät umzubauen. Also bin
ich beigegangen und habe es selbst versucht, und dies gleich mit Erfolg. Für 9k6 Packet-Radio-Betrieb darf der Frequenzgang
des Signals bekanntermaßen nicht beeinflußt werden. Dies bedeutet, daß man alle Frequenzbeeinflussenden Stufen sowohl im
Sende- als auch im Empfangszweig umgehen muß. In der Praxis heißt das direkte Einspeisung des Sendesignals am Modulator
und im Empfangsfall Abgriff des empfangenen Signals am Demodulator.
Beim IC24 ist es garnicht so schwierig, wie es im ersten Moment erscheint. Es ist ganz hilfreich, wenn man die Schaltung besitzt,
es geht aber auch ohne.

Wenn das Gerät geöffnet wird, legt man die Hälfte mit der LCD-Anzeige und dem Microcontroller nach rechts. Das heißt, die
Bedienungsknöpfe für Lautstärke usw. zeigen nach oben. Nun kann man sehen, daß in der linken Gehäusehälfte unten rechts
noch Platz für eine Mini-Buchse ist. Ich habe dort einen Ausschnitt für eine schmale 4polige Flachbuchse eingesägt und diese
dann mit 2-Komponentenkleber eingesetzt. Diese Art von Buchsen dienen als Mini-Stromversorgungsbuchsen in Floppy­Laufwerken, und sind im Elektronikhandel für ca. 2DM erhältlich. Den passenden Stecker gab es gleich dabei. 4polig reicht genau
aus für Sende-NF, PTT, Masse und Empfangs-NF. Man kann natürlich auch irgendeine andere Buchse dort unterbringen, wenn
man etwas findet, was klein genug ist.

Ich wollte die eingebauten Buchsen für Mic und Lautsprecher im Originalzustand lassen, weil das Gerät weiterhin über die
vorhandenen Buchsen für 1k2-Packet oder Betrieb mit Lautsprechermikrofon nutzbar sein soll.

Wenn man sich nun die Schaltung anschaut, sieht man das IC1 TK10487M auf der DET UNIT. Hier müßte man zum 9k6 Empfang
an PIN 11 rangehen, dann wären alle Probleme gelöst. Nun ist es aber leider so, daß man nirgends an diese Stelle herankommt.
Wenn man in die linke Gehäusehälfte schaut, sieht man ein paar kleine Platinen hochkant auf die Hauptplatine gelötet stehen.
Die ganz rechte davon ist die DET UNIT. Das IC sitzt leider auf der nach innen gewandten Seite, und unglücklicherweise mit dem
PIN 11 nach unten. Da kommt man also niemals ran. Der AF-Ausgang dieser Platine ist der letzte Anschluß nach oben zu den
Potis hin. Da kommt man notfalls ran. Nur leider ist auf dem Weg von PIN 11 zu diesem Anschluß schon ein Tiefpass eingebaut,
der 9k6-RX an dieser Stelle nicht mehr möglich macht. Dieser Tiefpaß wird gebildet durch R8 (10k) und die beiden SMD-C's C28
und C29.

Glücklicherweise sitzen diese beiden Kondensatoren auf nach außen zugewandten Seite ganz am rechten Rand der Platine direkt
übereinander. Hier kann man auch mit einem Oszi an der rechten Seite der C's die empfangene NF messen. Die linke Seite der
C's geht an Masse. Wenn man nun die C's auslötet, kann man an dieser Stelle mit etwas Geschick einen Draht anlöten und zur
Buchse führen. Das hat den Nachteil, daß der NF-Frequenzgang etwas beeinflußt wird. Das macht sich so bemerkbar, daß die NF
etwas höher klingt, und höherfrequente Rauschanteile des Empfangssignals hörbar werden. Ich vermute, daß der Signal­Rauschabstand dadurch minimal schlechter wird. Aber das nehme ich in Kauf.

Ich habe also diese beiden C's ausgelötet, undzwar indem ich den Lötkölben (15 Watt mit feiner Spitze) an die rechte Seite der
C's gehalten habe und ca. 3-4 sekunden gewartet, bis die andere Seite auch genügend erwärmt war. Nun konnte ich mit einer
Lötzinn-Saugpumpe erst den oberen, dann den Unteren C von der Platine entfernen. Das ging bei mir einwandfrei, trotz kalter
Scweißausbrüche wegen der Möglichkeit, eventuell eine Leiterbahn abzuheben.
Dann nämlich hätte ich das Gerät wohl entsorgen können...hi. Wie gesagt, es ging einwandfrei und danach konnte ich an der
Stelle einen Draht anlöten.
Falls es nicht gelingt, wegen der Enge mit Lötkolben und Lötlutsche gleichzeitig da ranzukommen, muß man versuchen, die C's
soweit zu erwärmen, daß das Lötzinn weich wird, und sie dann mit einer Spitze wegschieben.
Das Ganze sollte dann ziemlich fix gemacht werden, damit die Leiterbahn auf der Platine nicht abgehoben wird.

Danach das andere Ende des Drahtes an die Buchse gelötet, und welche Freude, 9k6-Empfang ging auf Anhieb einwandfrei.Es
reicht bei mir schon eine Signalstärke von S1 - S2 auf der Balkenanzeige, um einwandfrei zu empfangen.

Das Sendesignal auf das Gerät zu geben, ist überhaupt kein Problem. Und zwar sieht man bei geöffnetem Gerät unten beim
Batterieanschluß eine Platine hochkant stehen. Das ist die MIC-Unit. Dort sind oben links zwei kleine Poti's. Vom
Batterieanschluß aus gesehen regelt das rechte davon die NF zum UHF-Modulator. Im Schaltbild sieht man, daß von dort eine
Leitung zum UHF-VFO geht. Der Schleiferanschluß zeigt nach unten. An den rechten oberen Anschluß bin ich mit dem 9k6­Sendesignal gegangen. Hier klappte es auf Anhieb.
Will man auf 2m 9k6-Packet machen, muß man entsprechend an das andere Poti gehen, mit welchem die NF zum VHF-Modulator
eingestellt wird.

Der nächste Punkt ist die PTT. Hier kann man an den Microkontroller an PIN1 gehen. Das ist linke Anschluß von der unteren
Reihe. Wem das zu heikel ist, kann die Leiterbahn verfolgen. Ein kleines Stück nach links unten in Richtung der Leiterfolie ca
5mm von der Folie entfernt geht die Leitung an einen SMD-Widerstand. Dort habe ich die PTT-Leitung angelötet. Man könnte
wohl die PTT auch auf die eingebaute MIC-Buchse geben, aber da ist schwerer ranzukommen. In die PTT-Leitung habe ich noch
einen 150kOHM-Widerstand einbauen müssen, weil der Punkt anscheinend sehr hochohmig ist. Er muß zum Senden gegen
Masse gezogen werden. Da die PTT-Schaltung im 9k6-Modem mit einem Universaltransistor geschaltet wird, und dieser nur ca.
50kOhm Kollektor-Emitter-Widerstand im unbetätigten Zustand aufweist, geht das Gerät schon davon allein auf Sendung. Diesen
Widerstand sollte man auch im Gerät selbst einbauen, damit sich an der Modemschaltung nichts ändert, und alles wie bisher
auch mit anderen Geräten benutzt werden kann.

Das war's dann. Damit klappte alles auf Anhieb einwandfrei. Es geht bei mir mit einem TX-Delay von 30 ohne Probleme. Das ist
nicht gerade wenig, aber immer noch besser, als überhaupt kein 9600Bd-Betrieb. Im Vergleich dazu kann ich diesen Parameter
bei meinem Quarzgerät auf 6 einstellen.

Viel Spaß beim Basteln, und dieses natürlich auf eigene Gefahr. Ich übernehme keinerlei Haftung für eventuelle Schäden. Ich
empfehle diesen Umbau nur Om's, die schon etwas Erfahrung im Umgang mit SMD-Geräten haben. Wenn hier etwas vermasselt
wird, ist es wohl schwer zu reparieren !

73 de Fred, DL6BAW @ DB0CL

This modification is read 746 times.

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19-07-1998

(IC-24) Tip to to function bottom for IC-24

The Icom IC-24AT (and IC-2SAT) Second Keyboard Functions are activated by pressing AND HOLDING the "FUNCTION" buttom
on the side of the transceiver WHILE pressing the keypad with the desired 2nd function. The disadvantage of this procedure is
that it requires 2 hands to activate a 2nd key function, 1 to press AND HOLD the FUNCTION button and 1 to press the keypad
with the desired 2nd key function.

The Solution:
I modified the operation of the FUNCTION button so that it only has to be pressed MOMENTERLY to activate the function mode, it

remains in the function mode for approximately 4 seconds thereafter. Any second key functions may be selected any time during
the 4 second interval the function mode remains active. The beauty of this feature is that now you can squeeze the FUNCTION
button with your thumb and then have up to 4 seconds to select the desired 2nd key function with the index finger of the same
hand!

The Mod:
Implementing this modification requires one 4.7uF 10 volt chip capacitor and one 1K Ohm chip resistor. The negative terminal of

the chip capacitor is soldered to ground. The 1K Ohm resistor is soldered directly to the positive terminal of the chip capacitor.
The other terminal of the chip resistor is soldered to the FUNCTION key PC board contact via a small length of fine wire. THATS
IT! It works great! I had mine in operation for over 1 year. I could NEVER go back to the original procedure!

This modification is read 814 times.

19-07-1998

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(IC-240) 12,5 Khz mods for IC-240

Here are mods for putting 12,5 kHz step frequency for this rig. The basic step frequency is normally 25 kHz, and the rig uses a
diode matrix board as a "memory" for 22 channels.

The modifications are useful if you have put frequencies for repeater in your chart. After upgrade, you can access to 12,5 kHz
bandplan, and the total of channels will be 2x22 = 44.

The modifications are based on 3 features, that is to say:

● PLL mods for 12,5 kHz step

● deviation adjustment for narrow FM (+/- 2,5 kHz)

● improving selectivity in IF amplifiers (455 kHz), receiving part

1) PLL mods for 12,5 kHz step
All mods are done on PLL board located on the bottom of the rig. The first thing to check is the frequency of X-tal X1. It must be

6,4 MHz. You can measure the value of frequency at pin 11 (25 kHz) and pin 12 (12,5 kHz) of IC6 (uPD4013). This part of IC is
used as divider by 2, so the reference frequency for the phase comparator IC1 (TC5081P) is 12,5 kHz. How lucky we are! You
can adjust perfectly the value of the reference frequency with C2 trimmer capacitor.

The main modification is done by changing the loop divider ratio (half part of IC6 and IC1). Depending of the programming, the
total ratio of dividing is between 128 and 288 but always with even ratio_(128, 130, 132...286, 288).
The explanation is given by the fact that the second part of IC6 (uPD4013) used as divider by 2 is in front of programmable
divider IC1 (TC5080P) which gives 64 to 128 dividing ratio. In order to access 12,5 kHz step, the total dividing ratio must cover
values such as 129, 131, 133...285, 287).

Consequently, we have to replace half part of IC6 (uPD4013) and IC1 (TC5080P) by a new and single programmable divider. For
doing this job, the MC145151 has been choosen. With this IC, we just use the programmable divider part. Practical job is done
by using a small piggy board supporting the MC145151. An IC socket is soldered instead of IC1 (TC5080P), and the small board
is plug on it. This board can be something like bicc veroboard. Do not worry about frequency problems, because the highest
value encountered is about 3,6 MHz.

If there is a 10 kohms resistor between pin 1 of IC6 (uPD4013) and pin 15 of IC1 (TC5080P), you have to desolder it. On this pin
15, you have to solder a capacitor of 220 pF to pin 3 of IC6 (uPD4013). Mount this capacitor on the copper side of the PC board.
Now the piggy board has to be wired following this chart:

MC145151 pins IC1 socket pins remarks

(1) (15) f in
(2) (9) ground

(3) (13) + 9 V
(4) - not used
(5) (9) grounded
(6) (9) grounded
(7) (9) grounded
(8) - not used
(9) - not used
(10) (10) f: out
(11) external wire N0 (see text below)
(12) (1) N1
(13) (2) N2
(14) (3) N3

(15) (4) N4
(16) (5) N5
(17) (6) N6
(18) (7) N7
(19) (8) N8
(20) (9) grounded
(21) - not used
(22) (9) grounded
(23) (9) grounded
(24) (9) grounded
(25) (9) grounded
(26) - not used
(27) (9) grounded
(28) - not used

Note that instead of pin 9 for socket IC1, you can use also pins 11 or 12.
N0 is the bit of lowest magnitude. When N0 is at zero logic level, you access to "normal" frequencies (divider ratio is even), with

25 kHz step.
When N0 is at one logic level, you access to "normal + 12,5 kHz" frequencies, (divider ratio is odd). On my rig, I use a simple
switch on the front panel of the rig. it is mounted instead the 1750 Hz pushbutton. The 1750 Hz is now remote through a
pushbutton mounted inside a microphone (pin 3 of microphone socket is free for this use).

N0 is wired through the mid point of the switch with a pull-up resistor on + 9 V. The other point of the switch is grounded.
After doing this, it requires no more adjustement. However, because of the PLL system, using a mix frequency of 131,7 MHz

(three times 43,9 MHz freq. of X-tal X2), it is better to check the exact transmit frequency. Fine adjustment is possible through
trimmer capacitor C38.

2) Deviation adjustment for narrow FM (+/- 2,5 kHz)
In order to comply with 12,5 kHz step frequency, it is necessary to adjust the deviation. It could be done with a deviation meter,

but this instrument verder, (A)fbreken, (C)verder geen pag. of (N)volgende ber. -->is not easy available. Here is an alternative
method which provides good results (checked with a deviation meter). All the adjustments are done on the main board, which is
located on the top of the rig.

● turn the R132 potentiometer (AF gain) for maximum gain,

● turn on the 1750 Hz and check the audio level at mid point of R112 potentiometer, you could read with an oscilloscope

about 3,2 V peak to peak. This value is right for +/- 5 kHz deviation. Now reduce the value to 2 V peak to peak with R132.
The resulting deviation is +/- 2,5 kHz (exactly close to +/- 3 kHz depending of audio content).

● Adjust the R132 potentiomer (AF gain) according to your voice. For the adjustment of R132, you could also use the original

setting. But, NEVER adjust the deviation potentiometer R112 once more. This complete the deviation adjustment.

3) Improving IF selectivity (455 kHz) - receiving part
For 12,5 kHz step frequency, the IF bandwidth is sometimes wide. This situation is true when you turn to low signals with a

strong nearby signal. The solution is very simple. You have to replace two 455 kHz filters in IF part of the receiver. They are
easily available from MURATA distributors. The filters are located on the main board, which is located on the top of the rig.

● replace the two IF filters CFU455 E (black plastic case) by CFU455 G,

● for matching correctly these new filters, changing the following resistors by these new values:

R17 and R18: 820 Ohms (instead of 470 ohms)
R20: 5,6 Kohms (instead of 3,3 Kohms)
R14: 470 Ohms (instead of 1 Kohms)
R15: 2 Kohms (instead of 1,5 kohms)

No more adjustment is required. Sensitivity and signal to noise ratio are equivalent to original one. Closing channels are now well
rejected.

This complete the mods done with success on my old rig. For information, I have already change the 1750 Hz PC Board by a
cristal controlled one. Drift problems belong to the past. If anyone knows upgrade mods for this reliable and rugged rig, I am
also interested. Many thanks, and hope reading any of your comments.

PS!!

Please, note that the deviation adjustment is done by decreasing AF voltage from 3,2 to 2 V peak to peak with R112 and not
R132 as mentionned.

73 de Jean-Roger / F6EGK @ LX0PAC.LUX.EU.

This modification is read 401 times.

19-07-1998

(IC-2400) ICOM 2400A mini repeater function

1. CUT D9 (MAY NOT BE REQUIRED NOT IN ALL RADIOS)

2. TURN OFF POWER

3. PUSH AND HOLD MONI, MHZ, SET BUTTONS & MIC DOWN BUTTON

4. TURN ON POWER

5. RELEASE ALL BUTTONS

ICOM 2400A repeater function cancel

1. Push and hold set button

2. Then depress MHz
NOTES:

If your rig has D9, the diode above it will expand the 440 band recive if it is cut also.

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To find d9, look at the back of the face plate inside radio on left hand side, you should see a vertical line of 7 diodes, D9 for
repeater is 2nd from the bottom and 440 expanded recieve is the 3rd one from the bottom. This is kinda hard to explain, as of
this writing there are no service manuals available, but icom will send you the mod with a photocopy of the mod if requested.

Call GARY FIBER KF7XV, ICOM TECH. CUSTOMER SERVICE REP. AT PHONE # [phone], OR FAX AT 206-454-1509.

This modification is read 767 times.

19-07-1998

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(IC-2400) IC-2400 144/430 9K6 mod

Sezione uhf

Ritenendo di fare cosa gradita a molti utilizzatori del suddetto apparato ho deciso di proporre a mezzo bollettino packet la
modifica da attuare per utilizzare detta radio a 9600 bauds.

Innanzi tutto, mi preme specificare, che la modifica molto semplice a prova di bambino dal punto di vista elettronico ma alquanto
ardua dal punto di vista meccanico vista la costruzione massiccia di tale radio che non lascia molto spazio a voli di fantasia per il
passaggio dei cavi necessari al collegamento al modem. Mettetevi quindi calmi e calcolate una buona oretta di lavoro.

Procuratevi un cavetto schermato a quattro poli piu' calza il piu' sottile possibile, poi capirete perch, quindi un buon cacciavite,
una capiente vaschetta dove mettere le numerosissime viti, un saldatore di quelli piccoli piccoli per circuiteria SMD, forbici,
stagno e bisturi!

Aprite l'apparecchio ,le UHF sono nella parte superiore, Cercate sul circuito il quarzo CR125, posizionato su una basetta ripiegata
sul centro destra della radio vicino ai cavi dei toni sub audio, sollevate con delicatezza questa basetta e noterete saldato sul lato
saldature un integrato SMD il TK10420M. Bene una volta individuato, aiutatevi con una lente se necessario, trovate il piedino 11
dello stesso, che ad ogni modo il primo a sinistra, saldate su questo pin il cavetto di Ricezione dei 430
Sullo stesso lato, pero' sulla sinistra, troverete una scatola in metallo saldateci la massa del cavetto schermato.

Per quanto riguarda la trasmissione la modifica risulta molto piu' ardua bisogna smontare il frontalino dell'apparecchio svitando le
4 viti , poi svitare il cavo ant. uhf svitare tutte le viti che fissano la scheda (attenzione che ce' da dissaldare un cavo fisso vicino
al finale tx ) ed mettere a nudo la scheda uhf.
la modifica va effettuata nella parte inferiore , armati di un sadatore sottile max 20w collegare il cavo schermato del tx sul pin 2
di ic2 che risulta un TC4S66F (lo schema elettrico ti sara' d'aiuto ).

Quando si parla di destra e sinistra si intende guardare la radio con il frontale rivolto verso di noi.
A questo punto le operazioni per la parte UHF sono finite, occorre recuperare la commutazione del PTT, che conviene prelevarla

direttamente dal bocchettone del microfono, per fare cio' occorre smontare il frontale della radio sono solo quattro viti, e quindi
armarsi di buona pazienza per cercare il punto esatto della commutazione, in quanto abbastanza arduo saldare sul bocchettone
stesso, io ho saldato un filetto volante (per ragioni di spazio) e sono quindi venuto al cavo pentapolare principale.
Adesso siete pronti per lavorare a 9600 bauds.

Un'ultima cosa non tenete molto lungo il cavo di uscita, consiglio di attenersi alle lunghezze di quelli delle antenne, e saldare al
termine di questo un bocchettone DIN pentapolare oppure un DB9, si da collegarvi poi con facilit un cavo schermato che va al
TNC.

Ho notato che l'IC2400 funziona perfettamente senza nessun problema
Spero la modifica sia stata chiara ed esaustiva, attendo eventuali suggerimenti o richieste di chiarimento, non abbiate timore nel

procedere verso i 9600 bauds non sono poi quella brutta bestia che uno pensa tutt'altro!
Buon Packet de

IK7RVX .. Raff.

This modification is read 725 times.

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19-07-1998

(IC-2410) Expansion of receive range

The following diodes are located on the Logic Unit circuit board. The Logic Unit circuit board sits behind the front panel of the
radio. To get to the board remove the top and bottom of the case. Now notice that the front section of the radio is a separate
unit from the main body of the radio. Remove the 4 screws holding the sections together but do not yet separate the sections.
Place the radio on a table so that it is right side up. Carefully start to separate the sections being careful of ribbon cables that
connect the front section of the radio to the rear. If you look at the back of the circuit board on the front section towards the
lower part of the radio, you will clearly see three glass diodes labeled D8, D9 and D10. You will know this is the right circuit
board because a lithium battery will be taped to it. These are the diodes to cut to get extended receive range as follows:

D8 320-399, 830-950 800 Mhz coverage requires new antenna input
D9 118-135
D10 400-479

This modification is read 760 times.

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19-07-1998

(IC-2410) 800 MHz antenna input

To receive 800 Mhz you need to add a new antenna input to connector J2 on the MAIN-B unit (UHF unit) which is the large circuit
board on the bottom of the radio. J2 connects to a the B-band board which is a very small daughterboard, that is connected to
the MAIN-B board. The service manual offers no description of this board but it apparently is the 800 Mhz front end.

Two parts are needed:
One 5 3/4" grey coax jumper (this is available from ICOM but it doesn't have a part number)

Either:
One OPC223 pigtail with UHF connector
or
One OPC166 pigtail with N connector

The grey coax jumper has a plug on one end that mates with J2 and bare leads on the other. The pigtail also has two bare leads
on one end. This same end also has a metal flange thats designed to screw onto the back panel of the radio after removing one
of the dummy caps on either side of the existing antenna pigtail.

Without going into too much detail, you must:
Remove the small metal cap nearest the bottom of the radio and next to the existing pigtail.
Remove the metal shield at the back section of the Main-B unit.
Solder the two pieces of coax together, shield to shield, center to center and screw this assembly on to the back panel.
Plug the grey cable into J2 and then reassemble the radio.

This modification is read 726 times.

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19-07-1998

(IC-2410) Cross-band repeat

An edited version from an ICOM info sheet)

1. Set frequencies for both UHF and VHF. If necessary, set transmit offset and tone.

2. Hold the "BAND" switch and the "SET" switch. The memory number display will flash the letter "L". This indicates the 2410
is in the "Mini Repeater" mode.

3. Transmission by PTT is possible. If PTT is operated, the band which is indicated by the flashing decimal point will be
transmitted on. This can be done even when in "Mini Repeat" mode. In other words, PTT has priority over the "Mini Repeat"
operation.

Transmitted band will be switched by the "UP" or "DN" key on the microphone. The flashing decimal point will indicate
which band will be transmitted on.

4. Mini Repeater function will remain even when power is turned off. To disable repeater function, hold the "SET" key until the
flashing "L" disappears.

Remote cross-band activation

To activate cross-band repeat remotely: after dialing "B", optional 3 digit code then "#", the command for cross-band repeat on
is "B", "D", "*".

To turn off repeat, dial "B", optional 3 digit code, then "#".

This modification is read 720 times.

19-07-1998

(IC-2410) IC-2410 Dual Band External & Mike Remote Codes

Call MR VFO CLR
1 2 3 A

VHF UHF High Acs
4 5 6 B

Vmoni Umoni Low Spch
7 8 9 C

Dwn Mute Up Ent
Please enter a blank line to continue, anything else to halt output
* 0 # D

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Other Functions

B# or B???# = External On (?=password) Further protection used Tone/Squelch
B* = External Off

DB* = CrossBand On
DB# = CrossBand Off

DC = Speech Transmit Freq.

Notes

● 4,5,7,8,0 Function not available via External Remote Control????

● C Function not available when in CrossBand Mode????

● Display debate, don't know why the original display was boycotted, but I seen both & had a choice. I preferred the original,

lovingly refer to, as stealth. Think twice, before you get the other one.????

● There are diodes to be installed for some features, like transmit in Please enter a blank line to continue, anything else to

halt output rest of UHF ham band (420-450) and extended receive..etc. Check your local authorities, regarding scanning
laws.

This modification is read 709 times.

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19-07-1998

(IC-2410) IC-2410 Modification area as follows. New and old version

For OLD version

1.
Turn on the radio wtih pressing [V/MHz] + [SET] + [DN]on microphone.
That's All!!!

X-band reperter modification
Cut diode [D2] on back side of front panel.

Press [BAND] + [SET] more than 1 sec. cancel => press [SET] more than 1 Sec.
For NEW version

1. SEE THE BACK SIDE OF FRONT PANEL.

2. YOU CAN FIND Li BATTERY.

3. CUT [W27] or [D10] & [D8]

4. Reset the radio.

After modification , you can recieve
118 - 135.995MHz AM
136 - 174MHz
320 - 479MHz
830 - 950MHz
But 830 - 950MHz , you need to add ant for this band. open the lower panel , you can find [J2] ant connector.

This modification is read 717 times.

19-07-1998

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(IC-2410) IC-2410 TX modification

Both bands
Replace the one sided D-14 on the logic board with a 1SS181 two sided diode, and short the solder tabs (position W3) which are

directly below the location for D-14.
Result:

136-174 Mhz tx
400-479 Mhz tx

This modification is read 764 times.

19-07-1998

(IC-2500) Run 9k6 with an Icom IC-2500 (70cm/23cm TRX)

Yes it's possible to run 9k6 with an Icom IC-2500 (70cm/23cm TRX).
I BELIEVE the 2m/70cm version (IC-2400) is similar to modify (Hopefully!)

Here's my little description:
RX:

Pin 1 (=MDET) on the DET SW-Unit (mainboard A)
Note:

You receive on this Pin signals of that band, witch ist selected in the main display
TX:

You can take the Signal from R73, R72 or C137
Note:

as written above

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Comment:
These TRX is accorded to my experiences relatively good qualified for 9600 Baud Packet-Radio Signals.

This modification is read 550 times.

28-03-1999

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(IC-2500) Umbau des ICOM IC-2500E auf 9600 Baud

1. RX:
NF an Punkt 1 (MDET) der DET SW-Unit auf Mainboard A abgreifen und z.B. auf Punkt 8 der Mikofonbuchse fuehren. Vorher LS­Leitung von Punkt 8 entfernen.
Es steht dann sowohl 70cm als auch 23cm vom Diskriminator zur Verfuegung. Punkt 8 der Mike-Buchse geht dann auf NFRX am
TNC. (Evtl 10 Ohm Widerstand im TNC entfernen!!)

2. TX:
Verbindungspunkt R73 (Hub 70cm),R72 (Hub 23cm) und C137 auf dem Mainboard A mit Punkt 4 ( NC ) der Mike-Buchse
verbinden! (Leicht zugaenglich nach abschrauben und umklappen des Bedienkopfs) Punkt 4 dann mit NFTX vom TNC ueber einen
10uf-Elko verbinden.
Mit einem Scope Tonrufamplitude an o.g. Verbindungspunkt messen. Dann Datensignal vom TNC auf etwa gleiche Amplitude
einstellen! Das wars auch schon!

Dies ist zwar eine Simpelloesung - lauft aber hier hervorragend!
Fragen bitte an DL2GA @ DB0AAB!
Viel Erfolg dann mit 9600!

This modification is read 523 times.

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19-07-1998

(IC-251) Modifikcation af IC-251 for 9600 baud

Digital modulation applied to top of deviation pot at the junction of R58, R60 and R61 (just below Q13 on circuit diagram).
Modulation voltage from standard G3RUH 1200 bps modem wasn't high enough but was boosted by component changes on the
modem board. A higher voltage is required from the G3RUH 9600 bps modem; output level pot set to about four fifths of
maximum and works well.

PTT connection made inside the rig to the appropriate pins on the rear panel's accessory socket - no complications here, my
TNC's PTT comes from a reed relay.

No modifications done for digital output from receiver (yet).
Have investigated modifying to provide up/down control but checks are incomplete. Suspect provision of this facility is possible

and have identified (display) DRIVER IC2 pins 3/11 as the likely place to apply it.
Once AO-21/Rudak starts with higher speeds I'll probably expedite the provision of receive output and up/down control.

This modification is read 766 times.

28-08-1999

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(IC-251) Modifications for the ICOM IC-251

Author: Martin - G1GYC - [e-mail]

1987

SSB & CW VARIABLE POWER

Place set with the controls towards you and remove lid. If necessary check FM and CW power. Connect set to known good
dummy load and power meter.Locate R13 and R14 on the small board behind the front panel RF power control. With RF power
control on max, TX on FM and adjust RH pot(R13) for 10-12watts. Turn RF power control fully down and adjust LH pot(R14) for
desired low power setting (min 200mw). Short key jack at rear of set, switch to CW, TX and adjust R129 for 10-12watts the
same as on FM. Switch off power. Locate the brown wire to the left of the Xtal filter it runs from next to R258 to near R327 its
marked with a small b on the main unit board layout diagram. Cut this wire at the front end and solder to the emmiter of Q65 or
the purple lead marked I on the main unit layout. Solder the slider of a 4.7k preset to the LH end of the resistor behind R14,then

solder a 3.3k resistor to one leg of the preset, run a wire from this resistor to the top of R272 (scrape the paint off before
attempting to solder).

Switch on. Switch to CW, TX and with front panel RF power control fully down adjust the(4.7k preset for desired low power level
(min 200mw) SSB power is the same as CW. The front panel control now affects both FM,CW & SSB power levels.

The following modification was carried out to enable the front panel power control to be used on CW/SSB as well as FM.
The modification is in two parts (1) the front panel and (2) the main circuit board.

(1) FRONT PANEL

i. Remove four retaining screws and top cover.

ii. Remove four retaining screws and bottom cover, disconnecting the speaker.

iii. If you have a Mutek front end board fitted remove it now. MAKE NOTE OF THE CONNECTIONS TO IT! ***WRITE IT

DOWN***

iv. Remove the four front panel frame screws

v. disconnect the wiriing harness and remove the front panel. NOTE WHERE ALL THE PLUGS GO! ***WRITE IT DOWN***

vi. Locate the orange wire linking the mode switch and the board behind the power control potentiometer.

vii. Desolder it from it's present position on the mode switch and move it to the common side of the switch. That completes the

front panel mod.

(2) MAIN CIRCUIT BOARD

i. Remove the internal PSU if fitted.

ii. Remove the VCO and screening plate on the underside of the main circuit board.

iii. Now turn the rig over and find the brown wire that places TX9V(FM) on to Q64/Q65. If you look at the board layout in the

manual the wire runs from sectors 3F to 4F and is marked "b".

iv. Cut this wire where it joins the board, near R327/R46.

v. Now find the purple wire marked "k" on the board layout on the edge of sectors 5F/6F, locate this point on the underside of

the PCB.
I did this by standing the rig on one side panel and shining a light upon the component side of the board. Pointing to the

wire with a pencil or radio driver and looking at the track side to see the shadows.

vi. Once you have identified the point on the trackside of the PCB desolder the wire and clear the hole that is left.

vii. Join the purple and brown wires, then solder them back into the hole from where the purple wire came from. If the brown

wire is to short replace it, as I did. I used a purple wire striped from a ribbon cable.
This now means that when the radio is switched to transmit TX9V is placed on to Q64/Q65 and not TX9V(FM) as before.

That completes the mod.

viii. Reassemble the radio in the reverse order to which you disassembled it, leaving the top cover off.

ix. The only thing to do now is to check that the rig still works ok and to reset the high and low power levels. This is done by

adjusting VR13(high) and VR14(low) with a power meter and dummy load connected to the aerial connector and if possible
a two tone audio generator feeding into the microphone socket at around 600mV should de used to set the rig up on SSB.
The power reading on the RMS power meter should be approximately half the PEP. When the desired power levels have
been set fit the top cover.

NOTES:

I found that the power control on SSB/CW tends to drop the power off rather quickly but if you use it in conjunction with the mic
gain control very low power levels are attainable (milliwatts). Since this mod was done, G8RCF Des Sayer has also completed the
same and when we last spoke said he had not experienced any problems. An ALC input is included in the multiway socket on the
back apron and if you are going to use the rig with a transverter for 6M, 4M, 70Cm, 23Cm or even HF, I suggest you look at a
method of using this input to control the drive to the external equipment and not the modified power control as it is far too easy
to forget to lower the power or to catch the control.
The afore mentioned note on ALC apart, this mod is useful to run a linear at a lower out put, e.i. I run my MML100s at 40 watts
or less as this stops breakthrough to a neighbours television set, yet alowing me to gain a higher ERP than just using the rig to
feed in to the aerial.
My thanks go to G8RCF who was the second one to modify an IC251 using the method I used to my knowledge. Hope you find

this mod of use as I have.
Any comments on how well the mod works would be apperciated to G1GYC @ GB7NWP

This modification is read 983 times.

21-04-2000

(IC-251) IC-251 Receive-repair

Author: Derk - PE4CL@PI8DAZ.#TWE.NLD.EU

Hello OM,
In case of suddenly loosing receiving of signals.

In this case you can only receive very strong nearby signals, but receiving is weak.
Also the RF-gain knob has no effect at all.

solution: The HF-amp is defect.

Replace the FET- 'Q47'
This is a dual-gate fet and the replacing type is BF960. (original 3sk40 is somekind)
or

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Going to work:
Desolder the fet q47 and replace it for a BF960.
With the front of the transceiver pointed towards you, and the components-side above, the next are valid:

G1 G2

S D

Your transceiver will now operate (tx & receive) fine again.

Good luck! Derk

This modification is read 852 times.

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19-07-1998

(IC-260) IC-260E auf 9600BD

UMBAU ICOM IC260E auf 9600BD FSK mit G3RUH-Modem (z.B.: DK9SJ-TNC2H)
Ich habe diesen 2m ALLMODE Transceiver (TX-seitig) auf 9k6 umgebaut um damit PACSAT (UO-22, KO-23) Uplink machen zu

können.
Die FM-Modulation erfolgt mit der Kapazitätsdiode D32, die den 10.75MHz Quarz- oszillator X2 / Q23 moduliert. Man muß jezt

nur das Signal vom G3RUH-Modem / TNC2H auf die ANODE von D32 geben. FERTIG. Masse kann direkt daneben an R113
angelötet werden.
Die beschriebenen Bauteile befinden sich auf der MAIN-UNIT, ziemlich direkt neben (Richtung FRONT) dem Loch für den
Lautsprecher. Man muß für den Umbau lediglich den UNTEREN Deckel des IC260 (2 Schrauben) öffnen.

Nach Messung erhält die D32 im 'Normalbetrieb' (mit Mikrofon) bei maximalem Hub genau 1Vss. Man braucht also nichtmal den
Pegel des 9k6 Modems zu verändern, weil der TNC2H auch 1Vss als Ausgangsspannung bringt.
Darüberhinaus hab ich mir mal die Beschaltung angeschaut, die sonst noch an der Anode von D32 hängt, und zusammen mit der
Ausgangsbeschaltung des 9k6 Modems durch PSPICE durchgelassen - der Frequenzgang müsste von ca. 5Hz bis über 10kHz
gehen. Also optimal. Gemessen hab ichs allerdings nicht.

Wenn das 9600Bd Modem eingesteckt und eingeschaltet ist geht natürlich die 'normale' Modulation nicht mehr, weil der
AusgangsOP des Modems alle Spannungsschwankungen, die er an seinem Ausgang kriegt über seine Rückkopplung sofort auf 0
ausregelt.

Empfangsseitig (das hab ich NICHT ausprobiert !!!!) verwendet der IC260 ein übliches FM-DEMOD IC. Den MC3357P. Das heißt,
man muß das RX-Signal nur an PIN 9 dieses IC's abgreifen und schon müsste es funktionieren.

Die PTT kann direkt an PIN 3 der Erweiterungsbuchse angeschlossen werden.
Zur Mechanik: In der Rückwand des IC260 findet sich noch die eine oder andere Möglichkeit ein Kabel durchzuführen. Ich hab

rechts hinten, über der Er- weiterungsbuchse, ein Loch gebohrt und das TX-NF Kabel da durchgeführt. In dem Eck ist sicher auch

noch Platz für ein RX-NF Kabel.
Für die NF-Signale müssen vernünftig geschirmte Leitungen geringer Kapazität verwendet werden.

Fragen bitte an DH1SAJ @ DB0RBS. MYBBS DB0SAO ist zur Zeit ohne Link.
73 de Jochen, DH1SAJ @ DB0RBS

This modification is read 429 times.

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19-07-1998

(IC-27) IC-27 mic-connector mods

For those interested in an alternate method here is what has been done by wb4fow on several other radios:
Since about 1985 most icom radios have pin 8 of the microphone connector wired to the speaker. This is convenient for the

wiring of a tnc and is usually easy to modify so that receive audio is taken from the high side of the volume control.
On the ic-27/37/47 radios, on the bottom side of the radio, since about 1985 most icom radios have pin 8 of the microphone

connector wired to the speaker. This is convenient for the wiring of a tnc and is usually easy to modify so that receive audio is
taken from the high side of the volume control.

On the IC-27/37/47 Radios, on the bottom side of the radio, just under the area of the speaker, is a two pin connector with a
green and red wire attached. The green wire is speaker audio and the red wire is +8 volts.

By cutting these wires and attaching the green wire to the high side of the volume control and atted wire to switched 12 volts.
A TNC can be wired to just the microphone connector and makes a clean installation provided the radio is dedicated to packet.
To get back to the subject of the alternate modification for the ic-3200a you can rewire pin 8 of the microphone connector to the

high side of the volume control and avoid the muting circuit but if you plan to leave the tnc wired permenantly to the radio and
also,to use the radio on voice you will need to change a resistor in the tnc so as not to load down the audio at the volume
control. The value of this resistor will have to be determined experimentaly.

If anyone requires more information or assistance with this matter feel free to call clark, wb4fow, at 305-594-4313 monday
through friday 10am to 6pm or leave a message in the wb2wpa or n4ldg pbbs's.

Good luck!

This modification is read 751 times.

19-07-1998

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(IC-27) ICOM IC-27H 2M transceiver for use with the 9k6

Here are the mods I made to my radio for use with 9600 baud modem. I hope they make sence to you...
How to modify the ICOM IC-27H 2M transceiver for use with the 9600 baud modem (for use with uosat-3)

+---------------------------------------+
¦ MAIN UNIT SIDE ¦
¦ ¦
¦ ¦
¦ +--------------------¦
¦ ¦ ¦
¦ +----------+ ¦
¦ ¦ VCO UNIT ¦ ¦
¦ ¦ x-----¦---------¦-- "x"= D4 1SV50.
¦ +----------+ ¦ Connect wire
¦ ¦ ¦ direct to cathode
¦ ¦ ¦ side of diode.
¦ ¦ ¦
¦ ¦ ¦
¦ ¦ ¦
¦ ¦ PLL UNIT ¦
+---------------------------------------+

Front of the icom ic27h. viewed from bottom.
Bring a thin single core shield audio cable through the hole on the rear of the set where the power cable comes out, there was

quite enough space on my radio. Feed this cable up the side of the radio to the front panel and along to the PLL UNIT where the

other wires come in. Take the cable over to the VCO UNIT enclosure, where there are 2 small holes. Pick the hole closest to D4,
solder the shield to the outside of the metal case and feed the inner conductor through the hole and direct solder to the cathode
of D4 1SV50, keep the lead as short as possible.

This modification is read 740 times.

19-07-1998

(IC-2700) IC-2700 RX/TX expansion

RX Expansion Modification

1. Remove Top Cover. (6 Screws)

2. Remove Bottom Cover. (6 Screws)

3. Remove Front Display. (4 Screws)

4. Locate the Logic Board.

5. Remove W1 from the logic.

6. Hold [SET], [SPCH] and turn radio on.

Expanded Frequency Range

AM Mode 118-136 MHz
FM Mode 138-174 MHz
350-470 MHz

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Tx Expansion Modification

1. Remove D16 and D17

2. Hold [FUNC], [A], [CLR] and turn the radio on.

Expanded Frequency Range

FM Mode 138-174 MHz
350-470 MHz

That's what Icom's sheet said. I didn't follow it when I modified my radio and it worked very well. Here's what I did:

1. Remove power and antenna from the rig.

2. Remove the face plate from the rig (careful with the small hookup cable that attaches to the logic board).

3. Locate the "Zero-Ohm Resistor" W1 and cut it out with a fine-tipped set of wire cutters. W1 is clearly marked on the board
and is along the top edge, just to the right of center of the logic board. In my rig, W1 looked like a 1/8 Watt resistor, solid
white in colour.

4. Using the same pair of fine-tipped cutters, remove D16 and D17. They're the first two diodes slightly below W1, going
towards the LEFT side of the rig.

5. Carefully re-attach the face plate, mic, antenna and power.

6. Press SET and SPCH together and power on the rig. Keep the buttons depressed for about 4-5 seconds as the radio goes
through a reset. ALL MEMORY INFORMATION IS LOST!!!.

7. Re-program in your memories and there you have it!

Futile Attempt at a diagram:

Front View with face plate detached.
________________________________________________________________________
| DDDDD W |
| |
| D67 |
| ____ |
| |HEAD| ___ |
| ~~~~ |MIC| |
|______________________________________________________________________|

Where D = Surface Mount Diode Package
W = Jumper W1

6 = Diode D16
7 = Diode D17
HEAD = Face Plate Connector
MIC = Mic Connector

I hope that the diagram and description are clear enough to follow.
For X-Band repeating, the only information that Icom game me was a brochure entitled "With Icom Radios, Crossband Repeating

Has Never Been Easier!" In short, the only way I've been able to find to get the 2700 to x-band repeat is to put it into remote
mode and use the appropriate DTMF code to turn it on. It works fine in this mode. I've done extensive testing and all these
functions appear to work fine:

DTMF CODE FUNCTION
========= ========
B, XXX, # Remote function ON (XXX = 3 digit password)
B* Remote Function OFF
DB* Cross Band Repeat ON
DB, XXX, # Cross Band Repeat OFF (XXX = 3 digit password)
1 Call
2 Memory
3 VFO
6 High Power
9 Low Power
DC Speech
D (+NNN) Enter (Direct entry of mem. chan. or VFO Frequency)
# Up
* Down
A Clear

That's all the information I've got to date. So far, I haven't been able to find a method of putting the rig into X-Band repeat
without using the remote control function. It'd be nice to be able to do that from the rig or mic.

Hope this information helps!
Ray Semenoff VE6RHS

Chief Engineer (and Bottle Washer)
CJSR FM
University of Alberta
Edmonton, Alberta, CANADA.

This modification is read 745 times.

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19-07-1998

(IC-2700) IC-2700 Cross Band Repeater

Removing D14 will allow use of cross band repeater and DTMF remote control functions.
Activate "hang up time" type repeater:
Push the VHF and UHF main knobs and the SET/LOCK key for more than one second.
Activate "no hang up time" type repeater:
Push the VHF and UHF main knobs and the SET/LOCK and DUP keys simultaneously for more than one second.
To return to normal mode, press SET for more than one second.

This modification is read 681 times.

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17-11-2000

(IC-2700) Enabling ICOM 2700H remote operation

Author: Paul Webster VO1HC - [e-mail]

This is further information to go along with Ray Semenoff's (VE6RHS) note on putting the IC-2700 into remote operation, either
from the front panel of the rig or from a remote transceiver.
First you must put the rig in the REMO mode, push the DTMF button one or more times until REMO is flashing to the right of the
left side channel display.

I played with this and followed the sequence given in the manual on page 63 to enter commands remotely and that to turn the
XBand rpt on, you need only put 'D' in the command part of the sequence. To turn the XBand rpt off, need only to omit the
command part of the sequence altogether.

i.e. - for XBand Rpt on B000# D B*
for XBand Rpt OFF B000# B*

Also, to enable the XBand remote from the front panel of the rig, press and hold the SET button, then immediately press and
HOLD the DUP button, and then press and HOLD both of the channel buttons until the flashing L appears on both sides of the
display.

Regards,

Paul Webster VO1HC

This modification is read 645 times.

19-07-1998

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(IC-271) PSK Transmit Audio Modification for ICOM IC275 & IC271

After reading a FUJI-OSCAR-20-PRBBS message from James, G3RUH, regarding the modifications he made to his Yaesu FT736 to
improve the PSK transmit audio, I decided to investigate the situation on my ICOM IC275H to see if the same problem existed. I
was certainly less than satisfied with the results I was getting in the first few days with FO-20 Mode JD. I was feeding the TX
audio in at the front microphone socket and results on the uplink were quite poor but my downlink copy was 100%.

The first change I made was to move the Tx audio to the rear connector, ACC1. Results improved but I was still not satisfied.
Some scoping around the Varicap diode, D40, revealed considerable distortion of the PSK audio. To prove if this was the cause of
my problem I studied the IC275 circuit to see how I could feed the TX audio in as close to the Varicap modulator diode, D40, as
possible.

In the IC275H there are several Audio feeds to D40, including 3 via Q33, and in my unit one of these, the feed from the Tone
Squelch is unused. P46 normally plugs into the Tone Sq card but as this option is not installed it is left unterminated inside the
rug. I also found that Pin 1 on ACC1 was unused so a shielded wire from P46, pins TSTN and GND to ACC1, Pins 1 and 2 would
give easy access from outside the rig to D40 and NOT alter any of the existing functions of the IC275H.

The installation of the wiring is not as easy as it sounds however:
(1) You have to find a way to connect P46. I stripped a small amount of insulation from the wires just behind the plug housing

and soldered the extension wire there.
(2) To gain access to ACC1 you must remove the PLL PCB that it is mounted on. With the board removed I soldered the

extension wire to the underside of the board taking care not to short out any surrounding tracks. The whole exercise took about
30 minutes.

You will probably need more audio level from you PSK modem (see changes recommended by G3RUH in his FT-736 discussion).
You can then use the pot, F151, in the IC275H to set the TX modulation level.

Results from making this change have been outstanding with many less retries on the uplink than previously. The waveform
being applied to the Varicap diode is now identical to the output from the modem.
Performance via LUSAT and PACSAT digipeaters have been equally pleasing. EXTRA hint: Use DWAIT=0 RESPTIME=0 and start
TXDELAY=100 ms and reduce to as low as possible for your radio - I use 30 ms.

A similar change could be performed on the ICOM IC271 by wiring to J12 on the Main Board. J12 is normally unused in
Australian IC271's.

Since the above article referred to G3RUH's FT-736 discussion, I sent a message to James Miller G3RUH on FO20 and asked him
to repost it on the bird. I had lost the copy I downloaded since I did not anticipate any need for it.

Jack - the notes about mods to the FT736R were specific to that machine, and won't be relevant to the IC735.

1. What you need to do is work out a way to belt the varactor directly. Then inject a square wave (1200 hz will do) and
measure the deviation that results.

2. You can do this measurement with either a proper deviation instrument or more likely with a monitor RX, by looking at the
output from it's discriminator.

3. You can calibrate the monitor RX quite easily, Tune in a steady unmodulated carrier and note the discriminator DC output
voltage Change the RX frequency by 1 Khz (knob on the RX front) and note the change in DC voltage. That gives you the
monitor RX sensitivity in volts per Khz.

4. Now return to the TX, and adjust that driving square wave to give you approx +/- 3 kHz, you want to see about 6x volts
peak to peak square wave on the monitor. (Somewhere between 4x and 6x will do, no more.)

5. Now return to the modem and juggle about with the TXAudio output components to achieve this level of drive signal, and
look at the monitor RX too.

6. When you have done this, which should take you all of 30 minutes, you should be in business. If you can't get square
waves TX to produce squarish waves out of the monitor RX, then the varactor dept. must be suspect, and so on.

All is fairly logical. Hope useful. Let me know the results.
73 de James G3RUH @ GB7SPV 1990 Mar 28
Since I am not going to be able to try the mods until I return from a vacation I won't be able to give you an answer as to

whether they work or not. But it is my opinion they will. What is happening is that between the mic connector and the varactor
the digital signal is being badly distorted and the bird does not respond to the digital signal. This would not make much
difference on voice but on a digital signal it makes all the difference in the world.

Please feel free to contact me further if I can be of any further help.
Best regards Jack W9FMW
Note:

From Bill K7RIE
ICOM has not tried this mod nor have we verified this problem.

This modification is read 731 times.

19-07-1998

(IC-271) VOX of an IC-271,471,1271 usable for FM

How to make the VOX of an IC-271,471,1271 usable for FM :
1'st type of 'main-board' :
The only thing to be done is to add a diode such as 1n4148 or bax13 on the MAIN board on the position D74

When D74 is inserted ... the vox works in FM also.
The diode is on the shematic diagram of the Main board but is not mounted on the pcb in the factory.

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73's de stefaan
ON4BY @ ON4HU
16/03/1990 18.31 h

2'nd type :
(On this board a D74 is present (near PA- and RF-YGR- Unit))
(It might be not present in the plans !)

Disconnect the cathode of D69 from it's old postition. It's new position is the cathode of D50 or D51

name ! position on main board ! (old) function !
D69 ! near 'CW-DELAY'. ! 'FM -VOX-OFF' ! FM 8V
D50 ! near 'RF-YGR-Unit' ! 'USB-VOX-ON' ! USB8V
D51 ! near 'RF-YGR-Unit' ! 'LSB-VOX-ON' ! LSB8V

20/03/1990

This modification is read 685 times.

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19-07-1998

(IC-271) IC-271 / 471 fuer 9k6

es kommen doch noch anfragen wie man die 271/471/(1271?) geraete von icom fuer 9600bd umbaut.
hier nochmal allgemein:

fuer den empfang geht man an den pin 9 des ics MC3357 auf dem main-board. fuer die rx seite wars das schon.
fuer tx verfolgt man den weg vom evtl. vorhandenen tone-unit zum main-board. dort sollte die leitung ueber einen widerstand

an eine varicap-diode gehen.
das ist auch der punkt an dem man das modem anschliessen muss.
es ist sehr ratsam direkt an die diode eine ferritperle mit einer windung anzuloeten, und dann erst auf das g3ruh modem zu
gehen.
(gleichniss "pferde vor der apotheke" HI) das wars auch schon.
diese allgemeine umbauanleitung kann fuer die 271er und 471er geraete (a/e/h) benutzt werden. danach haben einige andere
oms auch ihre geraete umgebaut.
(ihr solltet erstmal meine englische anleitung lesen HI)

hier jetzt speziell fuer den 471h.
fuer den empfang braucht man nur eine 2pol. stecker(weibl) den man auf den j-14 (der bei mir unbenutzt war), auf dem main­unit, aufsteckt.
fuer den sendezweig geht man mit dem signal, auch auf dem main-unit, am besten an die kapazitaetsdiode d4. und zwar an den
knotenpunkt r271-c18-d4-c17. die zuleitung sollte mit einer ferritperle abgeblockt sein.

ich hoffe mit diesem schaltungsvorschlag konnte ich jemandem helfen.
vy 73 de detlef dd1eg
p.s. dieses geraet benutze ich auch um via uosat-d qrv zu sein.

This modification is read 676 times.

19-07-1998

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(IC-271) IC-271 sounds raspy in SSB/CW

05-08-1998

Hello dear OM,
thanks for reading this bulletin.
I have an Icom IC-271 since several years. Recently the sound in SSB or in CW sometimes becomes raspy, both in TX as well as
in RX. The problem is intermittent and also the 'raspyness' varies.

I already found some hints at the Icom America website, where they describe a similar problem. They advise to replace
electrolytic capacitor C2 and replace 2 plastic trimmer caps by ceramic ones. I tried this, but it did not cure the problem.

Is there anyone out there who has had this problem and knows the solution? Please send me a reply or send an email to
[e-mail]
Thanks in advance,
73 de Allard PE1NWL
Amsterdam, Netherlands

This modification is read 733 times.

30-03-2001

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(IC-271) RAM Card Backup Battery Replacement Instructions

Author: ICOM

In the early 1980s Icom America marketed a group of transceivers and radios that utilized the latest state-of-the-art computer
technology to enhance the operation of the radios. This technology improvement allowed hams to afford a reasonably priced high
performance transceiver which until then was only available on units costing much more. Features now available to the hams
included: higher frequency stability, better frequency resolution, digital frequency display, almost instant recall of saved
frequencies (memory channels), quick mode signal processing and built in tones and offsets for the rapidly emerging repeater
operation.

Implementation of all these features required a CPU with associated logic circuitry. In the early 80s, the most cost effective way

to implement data processing and memory functions was through a DRAM (Dynamic Random Access Memory) to control the
CPU. This DRAM was a volatile memory integrated circuit which required a lithium battery to retain its instruction set. The
following receivers and transceivers had such RAM units:

IC-271 ; IC-471 ; IC-1271 ; IC-745 ; IC-751/A ; IC-R71A

The lithium batteries in these units typically lasted about 5 to 7 years before replacement was required. This was specifically
noted in each of the Owners Manuals for the products.

This lithium battery can be replaced by the radio owner if care is used. The following is a recommended procedure to accomplish
this:

Procedure

1. Disconnect the power cable from the radio, and take the cover off.

2. Unplug the RAM board and remove it from the radio.

3. Temporarily solder a 3 Volt DC battery source across the existing battery terminals (see suggested connection points on the
circuit board pictures).

4. Unsolder the old lithium battery and replace it with a new one. (BR2325 1HC, ICOM stock number 945 03112)

5. Unsolder your temporary 3 Volt DC source.

6. Reinstall the RAM board into the radio.

Cautions

1. Do not use an AC powered 3 Volt DC source, your grounded soldering iron tip could short out the battery (+) terminal. Use
a 3 Volt battery DC source only (2 alkaline cells for example).

2. Do not solder the external DC wires directly to the lithium battery tab pads. If you do so, you will not be able unsolder the
battery without having the wires drop off.

3. If by accident you lose power to the RAM unit it must be sent to Icom America for reprogramming.

4. Be careful not to damage or bend the connector pins on the radio side while removing or reinstalling the RAM card.

Pictures

There are two versions of the ICOM RAM boards. Both are identical in operation, and they are interchangeable. The differences
are in the circuit board layouts only. Note that the black and red wires visible on these images are the suggested way of
connecting the external DC backup voltage while the battery is being replaced. The wires are not a part of the RAM card, and
should be removed when the battery replacement procedure is complete. Refer to the replacement procedure outlined above.

RAM card version A images:

RAM card version B images:

This modification can also be found at ICOM's own homepage on the following URL: "RAM Card Backup Battery Replacement

Instructions"

This modification is read 729 times.

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03-02-2000

(IC-2710) Some modification for IC-2710

Maximum supported frequency range:

● VHF, 118-135.995 MHZ RX, 136-174 MHZ TX & RX

● UHF, 320-399.995 MHz RX, 400-479 MHz TX & RX

● UHF, 849-869 MHZ & 894-950 MHz RX

See product literature for frequency limits from factory. Please note, these are the "tunable" frequency ranges only. The
receivers are optimized over 20-30 MHz ranges which have been centered around the ham bands at the factory. Performance
outaide the ranges defined in the product specification is not guaranteed.

AM/FM mode selection (118-135.995 MHz or 320-399.995 MHz RX only:

● Select an appropriate frequency (left side display only)

● Push and hold the left side MONI(SQL) switch for about ONE second to toggle AM mode ON or OFF.

● The symbol "<" appears to the right of the frequency when AM mode is enabled

Frequency range modification:

● Remove Power and Antenna Leads

● remove the bottom cover of the radio

(See section 16, Page 65 of instruction manual).

● Viewing the bottom of the radio, orient the chassis with the fan to the right (front of radio to the left)

● refer to the drawing and locate the identified components on the main board in the lower left of the radio

To ennable receive on all supported frequencies:

● Cut jumper "W-18"

To enable only some RX frequencies:

● Remove "D-134" to enable receive on 300 & 800 MHz frequencies, or

● Remove "D-132" to enable receive only 300 MHz frequencies

To enable extended transmit ranges:

● For extended VHF TX range, remove "D-135"

● For entended UHF TX range, remove "D-136"

This modification is read 1166 times.

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12-11-2000

(IC-2710) Crossband Repeater Operation for the IC-2710

Author: Kevin - [e-mail]

Cross Band Repeater Mode:

● First, verify D-139 is not present (for non USA Versions only)

To ENTER Cross Band Mode:

● Set the desired frquency, tone, & offset on both bands

● Press [VHF} and [UHF] main knobs and the [SET L] key at the same time (An "L" will appear on the display)

● For zero hang time, also press the [LOW] key with the above three key command.

To EXIT Cross Band Mode:

● Press [SET] to exit Cross Band Mode

Remote Operation (UT-49 DTMF Decoder Unit Required for Remote Operation)

1. Set the sub band frequency to receive a control signal (DTMF code).

● The optional tone squelch function can be used for the sub band to increase remote control reliability.

Password Setup

2. Program a 3-digit password into the sub band's code channel 5, if desired: (default is 000)

a. Push the desired band's tuning dial.

*Each band has separate code channels.

b. Push [DTMF] 2 times to turn the pager function ON.

* "P" appears in place of the 100MHz digit.

c. Push {(VOL)SET] to select the code channel setting display.

d. Rotate the selected band's tuning dial to select the desired code channel, 0-5.

* Code channel P cannot be used for programming.

e. Push [(SQL)MONI] or [(VOL)SET] to select the digit to be programmed.

f. Rotate the selected band's tuning dial to set the digit.
g. Repeat e and f until the last digit is programmed.
h. Push [DTMF] to set the code channel for "receive inhibit" or "receive accept."

* When "receive inhibit" is set, "SKIP" APPEARS.
* Code channel 0 cannot be set as "receive inhibit."

i. Push the selected band's tuning dial to exit the setting display

Remote Operation Continued (UT-49 DTMF Decoder Unit Required for Remote Operation)

3. Select the main band by pushing a tuning dial, then set the desired frequency for operation.

4. Push [DTMF] one or more times unil "REMO" appears to select standby for the remote control.

5. Set the operating frequency of the controller transceiver equal to the sub band frequency of the the IC-2710H.
* Make sure a tone frequency is set when using the optional tone squelch function with the IC-2710H.
* The external DTMF remote does not accept a control signal on the main band frequency.

6. From the controller transceiver, transmit the DTMF code as follows:

ENTER REMOTE MODE "REMO": B+XXX (password)+#

X-BAND ON: B+XXX(password)+#+DB*

X-BAND OFF: B+XXX(password)+#+B*

EXIT REMOTE MODE: B*

This modification is read 1061 times.

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19-07-1998

(IC-275) PSK Transmit Audio Modification for ICOM IC275 & IC271

From AMSAT-Australia Newsletter #59 (Graham Ratcliff, VK5AGR)
After reading a FUJI-OSCAR-20-PRBBS message from James, G3RUH, regarding the modifications he made to his Yaesu FT736 to

improve the PSK transmit audio, I decided to investigate the situation on my ICOM IC275H to see if the same problem existed. I
was certainly less than satisfied with the results I was getting in the first few days with FO-20 Mode JD. I was feeding the TX
audio in at the front microphone socket and results on the uplink were quite poor but my downlink copy was 100%.

The first change I made was to move the Tx audio to the rear connector, ACC1. Results improved but I was still not satisfied.
Some scoping around the Varicap diode, D40, revealed considerable distortion of the PSK audio. To prove if this was the cause of
my problem I studied the IC275 circuit to see how I could feed the TX audio in as close to the Varicap modulator diode, D40, as
possible.

In the IC275H there are several Audio feeds to D40, including 3 via Q33, and in my unit one of these, the feed from the Tone
Squelch is unused. P46 normally plugs into the Tone Sq card but as this option is not installed it is left unterminated inside the
rug. I also found that Pin 1 on ACC1 was unused so a shielded wire from P46, pins TSTN and GND to ACC1, Pins 1 and 2 would
give easy access from outside the rig to D40 and NOT alter any of the existing functions of the IC275H.

The installation of the wiring is not as easy as it sounds however:
(1) You have to find a way to connect P46. I stripped a small amount of insulation from the wires just behind the plug housing

and soldered the extension wire there.
(2) To gain access to ACC1 you must remove the PLL PCB that it is mounted on. With the board removed I soldered the

extension wire to the underside of the board taking care not to short out any surrounding tracks. The whole exercise took about
30 minutes.

You will probably need more audio level from you PSK modem (see changes recommended by G3RUH in his FT-736 discussion).
You can then use the pot, F151, in the IC275H to set the TX modulation level.

Results from making this change have been outstanding with many less retries on the uplink than previously. The waveform
being applied to the Varicap diode is now identical to the output from the modem.
Performance via LUSAT and PACSAT digipeaters have been equally pleasing. EXTRA hint: Use DWAIT=0 RESPTIME=0 and start
TXDELAY=100 ms and reduce to as low as possible for your radio - I use 30 ms.

A similar change could be performed on the ICOM IC271 by wiring to J12 on the Main Board. J12 is normally unused in
Australian IC271's.

Since the above article referred to G3RUH's FT-736 discussion, I sent a message to James Miller G3RUH on FO20 and asked him
to repost it on the bird. I had lost the copy I downloaded since I did not anticipate any need for it.

Jack - the notes about mods to the FT736R were specific to that machine, and won't be relevant to the IC735.

1. What you need to do is work out a way to belt the varactor directly. Then inject a square wave (1200 hz will do) and
measure the deviation that results.

2. You can do this measurement with either a proper deviation instrument or more likely with a monitor RX, by looking at the
output from it's discriminator.

3. You can calibrate the monitor RX quite easily, Tune in a steady unmodulated carrier and note the discriminator DC output
voltage Change the RX frequency by 1 Khz (knob on the RX front) and note the change in DC voltage. That gives you the
monitor RX sensitivity in volts per Khz.

4. Now return to the TX, and adjust that driving square wave to give you approx +/- 3 kHz, you want to see about 6x volts
peak to peak square wave on the monitor. (Somewhere between 4x and 6x will do, no more.)

5. Now return to the modem and juggle about with the TXAudio output components to achieve this level of drive signal, and
look at the monitor RX too.

6. When you have done this, which should take you all of 30 minutes, you should be in business. If you can't get square
waves TX to produce squarish waves out of the monitor RX, then the varactor dept. must be suspect, and so on.

All is fairly logical. Hope useful. Let me know the results.
73 de James G3RUH @ GB7SPV 1990 Mar 28
Since I am not going to be able to try the mods until I return from a vacation I won't be able to give you an answer as to

whether they work or not. But it is my opinion they will. What is happening is that between the mic connector and the varactor
the digital signal is being badly distorted and the bird does not respond to the digital signal. This would not make much
difference on voice but on a digital signal it makes all the difference in the world.

Please feel free to contact me further if I can be of any further help.
Best regards Jack W9FMW

Note:
From Bill K7RIE
ICOM has not tried this mod nor have we verified this problem.

This modification is read 724 times.

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19-07-1998

(IC-275) IC-275 Freq. steps mod.

Titolo: Tuning steps change for all mode Icom IC-275/475/575/1275
The IC-275/475 FM-Step selectmatrix use these diodes on the front unit: (type 1SS53) D41, D42, D43, D44, (D45), D46
Note: diode D45 is not present but solder holes exist for it on the board just between D44 e D46
installed diodes are marked with X :

(*) (*)
D41 D42 D43 D44 D45 D46 D48 Steps DB4 DB5 DB6 DB7

. . . . . . . 10.0 Hz

. . . X . . . 100.0 Hz 1 0 0 0

. X . . . . . 1.0 KHz 0 0 1 0

X . X . 5.0 KHz 1 0 1 0

. . . . X . . 10.0 KHz 0 1 0 0

. . . (*) X X . 12.5 KHz (*) 1 1 0

. . . . . . X 25.0 KHz 0 0 0 1

X . X . . . . 1.0 MHz 0 1 0 1

(*)
To set a step of 12.5 KHz in FM mode (TS button off) it is not necessary disconnect the diode D44, just insert the diode D45
(IN4148 or similar) near D44 and "voil? les jeux sont faits".
Unscrew the two lateral screws and unlock the front panel.
Remove also all the connectors of the front board and after that unscrew ALL the screws of the metallic shield covering the front
board. It seems too much complicated insert the diodes from the component side of the front board, so it is better insert D45
from the solder side.

This modification is read 812 times.

19-07-1998

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(IC-275) Band Expand for ICOM IC-275E/H and IC-275A/H

To expand RX range delete D 44
To expand TX range delete D 27 install D 43
Range 138-174 MHz TX not in full range PLL lockout

This modification is read 952 times.

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19-07-1998

(IC-275) IC amplifier oscillates

Note: This service bulletin is meant for technical per­ sonnel with experience working on solid state com­ munications equipment. Damage caused by im­ properly installing this modification may cause
ICOM to charge for subsequent repairs to the
product. ICOM does not warrant this modification.

Bulletin #: 588-001

Subject: If the IC amplifier oscillates when the noise
blanker is turned on and the FL-83 CW narrow fil­ ter is installed

Procedure

1. Remove the covers to gain access to the main circuit board.

2. Remove R354 (22K) from the main circuit board and replace it with a 10K (ICOM P/N 915-01113) resistor.

3. Re-install the main circuit board and replace the covers on the radio.

This modification is read 702 times.

19-07-1998

(IC-275) Prevent PLL unlock at high ambient temperature

1. Change the following parts on the PLL board

Original New
Part Value Value

C101 12 pf 50V CH 6 pf 50V CH
R137 35D 45 SN (ICOM P/N 915-04229)
R133 22K 15K
C191 3 pf 50V 6 pf 50V

2. The thermister should be installed in series with R133. Unsolder one end of R133 and solder R137 in series with it.

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This modification is read 676 times.

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19-07-1998

(IC-275) Improve voice synthesizer and side tone audio

1. Remove C214 (.47 uf capacitor) from the main board.

2. Install a .1 mf 16V barrier layer capacitor in series with a 2.2 K 1/8W resistor from the emitter of Q58 and the base of Q59
on the foil side of the board.

This modification is read 662 times.

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19-07-1998

(IC-275) Prevention of PLL unlock at 174 MHz

1. Remove and replace the following components on the PLL Board

Original New
Part Value Value

R130 120 Ohm 270 Ohm
R131 47 Ohm 18 Ohm
R132 120 Ohm 270 Ohm
C42 60 pf 50V 30 pf 50V
C47 43 pf 50V 62 pf 50V

This modification is read 701 times.

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19-07-1998

(IC-275) Improve the stability of the center meter

Replace C81 on the main board (currently 120pf 50 CH type capacitor) with a 120 pf 50V SH temperature coefficient capacitor
(ICOM P/N 918-05960).

This modification is read 685 times.

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19-07-1998

(IC-275) Noise coming from speaker during transmit with audio turned up

Replace R125 (currently a 47K resistor) on the main board with a 10K resistor.

This modification is read 674 times.

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19-07-1998

(IC-275) Eliminate possible spurious emission when thermal switch has turned on during TX

May 1, 1989

Procedure

1. Remove top and bottom covers.

2. Remove PA section from radio.

3. Remove shield from power amplifier.

4. Replace R7 (originally 10K 1/4W) resistor with a 1K 1/4 watt resistor (ICOM part number 915-01165).

5. Replace R8 (originally 10K 1/4W) resistor with a 1K 1/4 watt resistor (ICOM part number 915-01165).

6. Replace the shield on the PA section.

7. Replace the PA section in the radio.

8. Replace the top and bottom covers.

This modification is read 671 times.

27-10-1998

(IC-275) Frequency range & CTCSS tones

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The IC-275 have capability to cover 138 - 174 MHz and the IC-475 has capability to cover 430 - 450 MHz. Because of hardware
restrictions they might not be fully up to specifications in all of the band, but an extended range can be interesting for e.g. use
with a transverter. It seems that the IC-275 has a parallel wide band preamp, that can be switch via the WBT pin on RF-YGR
PCB.

In the European versions the transceivers are wired for 1750 Hz repeater call, and they have no CTCSS capability. The
transceivers have a built-in CTCSS encoder, so these functions can be restored.

Both of these version dependent functions can be set by the diode matrix: D20 - D24 in the logic unit. I do not know the exact
mapping, but a lot can be derived from studying the different frequency ranges and the diode matrix coding table found on the
schematic diagram.

This modification is read 742 times.

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27-10-1998

(IC-275) Power control modification

Problem:
The power control circuit in IC-x75 is an ALC circuit. ALC circuits suffers from several drawbacks:

● slow reaction time due to time constants

● insufficient regulation due to low feed-back factor

These factors gives the problem that if the average power has been set to a low value (e.g. for driving a HPA), peak power can
still be in the order of 3-4 dB higher. This leads to either considerable side band distortion or a low average power output.

note: If you are always using your transceiver barefoot, without connecting any PA or transverter, this modification will offer no
benefit.

Solution:
The solution to these problems is to use a simple forward gain regulation without the feed back circuit of the ALC. The original

ALC is still kept for SWR protection only.
The ALC is working on gate 1 of Q13, which is a IF amplifier (9 or 10.75 MHz). The new power regulation uses gate 2 of Q13.

Therefore the two circuits can exist in parallel.
The modification should also give you a bigger dynamic range in the power regulation (lowest power < 5W on the IC-x75H).

Implementation:

● replace R87 (470k) with 100k

● cut "POCO" wire (pin 3, P1/J1, MAIN, orange) at the plug (P1)

● connect the "POCO" wire to gate 2 of Q13 (e.g. via top of R87)

● adjust R250 (SWR protection), R256 (low power level) & R259 (high power level) fully counter-clockwise. (this will give you

full SWR protection, but cancels the ALC in normal operation).

● put the front plate RF PWR in full output position (clockwise) and adjust R82 (Q13 output attenuator) until you have the

nominal output power (initially the output power will be higher because you removed the regulation, but the PA will be
saturated).

● the balance between FM, CW & SSB output can be adjusted with R137 (CW carrier level) & R105 (FM carrier level).

● other interesting adjustments: R135 (mixer balance i.e. SSB carrier suppression), R133 (TX BFO output level).

This modification is read 757 times.

27-10-1998

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(IC-275) Restoration of pass band tuning

Problem:
ICOM has chosen to remove the PBT in the later models, and replace it with a "data level adjustment". This change removes the

possibility to profit from the PBT in case of QRM or to use the PBT as a cheap CW-filter.
Furthermore the two extra IF-mixings is done with only a minimum of filtering, making the receiver very susceptible to spurious

IF breakthrough. This is often heard as high-pitch tones or as a high IF noise level.
Solution:
The solution is to re-wire the "data level" potentiometer so that it adjusts the PBT VXO-oscillator, and to re-install FI3. FI3 is a

455kHz ceramic SSB filter and can be bought under the type number: MURATA CFJ 455 K6.
Implementation:

● remove the capacitor (C61) fitted in place of FI3

● solder in FI3

● readjust R72 for proper IF gain

● cut wire PBTV (pin 4, P1/J1, MAIN, yellow) about 5cm from the plug (P1)

● cut wire AMO2 (pin 3, P2/J18, MAIN, red) close to the plug (P2)

● cut wire AMO3 (pin 4, P2/J18, MAIN, metal baird) close to the plug (P2)

● connect PBTV wire (the end not connected to the plug) with AMO2 wire (the end not connected to the plug)

● connect AMO3 (the end not connected to the plug) to +8V e.g. by tapping (pin 1, J4, MAIN, brown).

● connect the wire stubs on the plug (AMO2 & AMO3) together is you wish to use external modulation input for PACKET etc.

● adjust the coil next to X2 (PBT VXO) for correct middle PBT setting

This modification is read 707 times.

27-10-1998

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(IC-275) Modification of cw pass band (BFO)

Problem:
In these transceivers ICOM has chosen to shift the CW passband up 200 Hz compared to the SSB passband. This makes it more

difficult to copy SSB signals in CW mode.

Solution:
The extra BFO coil that is added in CW-R is short-circuited, and the BFO is re-adjusted for proper CW RX/TX-tracking and for

preferred USB/CW passband.

Implementation:

● short-circuit Lcw in the BFO compartment.

For readjusting the BFO you need another transceiver (TRX2) with correct tracking.

1. Receive on TRX2 and transmit in CW. Adjust the VFO (with the RIT off !) of TRX2 until you have the desired side tone in CW
mode. (e.g. 800 Hz - can be found by beating the tone with the side tone oscillator).

2. Transmit on TRX2 and adjust Ly (CW-R) until you have the desired side tone in CW mode. (you are setting the ~800Hz
difference between CW-R & CW-T).

3. Adjust Lx (CW-T) for preferred USB/CW receive passband.

You might have to repeat the tuning once again, as there is some interaction between the adjustments (diode switching for high
impedance RF circuits are not perfect !). If you would like to adjust the LSB passband, this should be done by adjusting the
capacitor C, before adjusting the coils.

Note: The BFO coils are switched in successively to give the required offset from the LSB frequency. Therefore adjusting CW-T
also changes USB/CW-R.

Re-adjusting all of the BFO frequencies is a good idea in any case to compensate for crystal aging. If the passbands sound
different in LSB and USB it is a sure sign of mis-alignment due to crystal drift - they should be more or less the same.

Disabling of SBB squelch

Problem:
Squelching is nice to have in FM mode, but it doesn't really work for SSB, where you will be looking for weak signals. Therefore

you have to adjust the squelch level every time you change mode. Furthermore I enjoy using FM as a monitoring mode on the
SSB calling frequency, so changing the mode happens quite often.

Solution:
The solution is quite simple. Just cut the connection to the SSB input of the squelch circuit in some way.

Implementation:
The easiest way to break the connection is to connect the base of Q7 to ground. The base is the lead facing into the centre of the

PCB.

This modification is read 667 times.

27-10-1998

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(IC-275) Disabling of SBB squelch

Problem:
Squelching is nice to have in FM mode, but it doesn't really work for SSB, where you will be looking for weak signals. Therefore

you have to adjust the squelch level every time you change mode. Furthermore I enjoy using FM as a monitoring mode on the
SSB calling frequency, so changing the mode happens quite often.

Solution:
The solution is quite simple. Just cut the connection to the SSB input of the squelch circuit in some way.

Implementation:
The easiest way to break the connection is to connect the base of Q7 to ground. The base is the lead facing into the centre of the

PCB.

This modification is read 660 times.

27-10-1998

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(IC-275) Very fast AGC

Problem:
For some modes of weak signal communication, it can be desireable to have a very fast AGC (e.g. meteor bursts with a sharp

rise and a long weak "tail"). The standard fast AGC has a time constant of about 2 secs (!), which also means that a noise pulse
can mute you for quite some time.

Note: Never use the noise blanker when receiving high speed CW (Meteor Scatter). The noise blanker mistakes the high speed
keying for noise pulses, and will seriously corrupt the signal.

Solution:
The solution is to move the "AGC fast" capacitor (C19) to replace the "AGC slow" capacitor (C20). You will loose the "AGC slow"
option, but I find "AGC fast" adequate for most signals.

Another solution is to switch out the "AGC fast" capacitor (C19) seperately, but then you will get the problem of finding an
appropiate front plate switch. I already tried to use the DATA button, but it cannot be activated in CW.

Note: a strong signal will be seriously distorted in AGC OFF mode.

Implementation:

● remove C20

● move C19 to the replace C20

This modification is read 671 times.

27-10-1998

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(IC-275) SSB RF Gain

Problem:
The RF GAIN function is different in FM and in SSB/CW modes. In FM mode the RF GAIN controls a PIN-diode at the input of the

preamp. In SSB/CW the RF GAIN simply activates the IF AGC.
The use of the preamp input attenuator (the PIN-diode) can be useful also for SSB/CW e.g. if you have connected a mast head

preamp with excessive gain. In this case the attenuator will help you to adjust the signal levels at the mixer, and thus reduce
intermodulation and blocking.

Solution:
The solution is to remove the SSB/CW RF GAIN for SSB/CW (this function is of little use anyway), and enable the FM RF GAIN

even in SSB/CW.

Implementation:

● Cut the lead (FM8V) conneted to (pin5, J6, potmeter PCB, green) about 4 cm from the plug

● Connect the short plug end with R14 (on the potmeter PCB) by soldering it to the end that is connected to the plug (+8V)

This will enable the FM RF GAIN in SSB/CW.

● cut R30 open

This disables the SSB/CW RF GAIN, and you now have a variable input attenuation with a dynamic range of 10dB (IC275 with
MI308/1nF) to 16 dB (IC475).

Note: The IC-275 might have a shared PIN diode for FM RF GAIN and TX/RX switching. If you choose to split up the RX/TX
paths, you must install a new PIN diode (MI301 or equivalent) on the RF YGR PCB to implement this modification. See the note
under the section dealing with spliting the RX/TX paths.

This modification is read 702 times.

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27-10-1998

(IC-275) Tuning speed

The tunning speed is set to a defaults of 100Hz, 1kHz, 5kHz or 1MHz depending on front plate setting and mode. These settings
can be manipulated by D41 - 46 at the front plate. At least a setting of 10kHz is also available.

This modification is read 679 times.

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29-10-1998

(IC-275) Splitting into RX- and TX paths

Problem:
This is a general transceiver problem. If you want to use the transceiver as part of a bigger setup (i.e. with external PA &

preamp or with a transverter), it is convenient to have separate access to the RX and the TX of the transceiver. Otherwise you
need two coaxial switches every time you add a new accessory. With split RX/TX paths you only need one switch - at the
antenna. Furthermore split RX/TX paths eliminates the need for a change-over sequencer.

On the other hand it is also nice to have the transceiver working normally when you are using it barefoot.

Solution:
The solution is to jump wire the RX path (between RX and the RX/TX switching) trough the rear side of the transceiver with 2

BNC connectors. In normal state these connectors are connected via a short cable. In case you need to "split up" the transceiver,
you remove the short coax cable, and you obtain direct access to the RX. The TX is still available using the common connector.

note: If you are always using your transceiver barefoot, without connecting any PA, preamp or transverter, this modification will
offer no benefit.

Remove the back cover. If you place the holes for the BNC connectors next to and aligned with the two existing DIN-connectors,
then ICOM have left enough space on the inside for the connections. You can also add other desired outputs like a phono plug for
AF OUT.

The RX cable runs between J4 on the RF YGR PCB and the PA unit.
note: In my IC-275H the PIN-diode for the FM RF gain is shared with the RX/TX switch and placed in the PA unit. This means

that the control voltage passes through the RX cable.
Therefore the breaking of the RX cable will cancel the FM RF gain function (the SSB/CW RF gain is working on the AGC and is not
affected). The solution is to install a new PIN-diode (D5) on the RF-YGR PCB. The PCB has already room for it. To avoid short­circuiting the control voltage the jumper placed in stead of C86 on the RF-YGR PCB, should be replaced by a 1nF capacitor.

This modification is read 691 times.

19-07-1998

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(IC-28) ICOM IC-28A AND IC-28H ext frq

To make the IC-28 transmit 138-174 MHz, cut D21 (no retuning required). D21 is a tiny glass diode standing on-end near the
center of the upper circuit board, accessible by removing the top cover. The IC-28 is the only convertible ham rig I know that
covers the 170-MHz federal government (including national park) frequencies.
[source: W9MKV]

Date: 16-01-2002

User comment

From:

Giovanni Luce, N8IWK

Subject: no cut 28-H mod
The 28-H can be modified by removing a wire from a connector that connects to d21. Simply trace the circuit from d21 to the

connector and pull the wire out by pressing the small metal tab on the connector and wrap it in electrical tape.
The radio then can easily be "unmodified" by simple plugging the wire back into the connector.
Unsure of pin# or connector number as I modified one over 10 years ago, and didn't bother to note pin or connector number.

This modification is read 1294 times.

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19-07-1998

(IC-28) The long, noisy squelch-tail of the Icom IC-28

The long, noisy squelch-tail of the Icom IC-28 (A or H model) 2-meter transceiver can be shortened by replacing C110 (4.7 uf)
with a smaller value (0.1 to 0.47 uf). (I can't remember the source of this information.)

I put a 0.33 uf in my IC-28H; it's a very worthwhile modification.
The capacitor is on the bottom board (the one with the lithium battery), just southeast of IC4 as you face the front of the upside-

down radio. The only difficult part is finding the right p-c pads to desolder on the back of the board.
To remove the board: Remove bottom plate, unplug speaker. Unplug coaxial antenna connector (gray wire). Other connectors

may remain in place. Remove 5 mounting screws, one in each corner and one near center. Tilt the board out of the radio. The
button in the upper left corner is CPU reset; you may have to reprogram the memories if it is pressed. Remember that, although
the radio is off, parts of the circuit are live so be sure not to short any part of the board during the modification.

This modification is read 1031 times.

05-06-1999

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(IC-2800) Icom IC-2800h Extended RX Mod

Before beginning, I naturally accept NO liability if someone screws up this mod! It is direct from Icom America, and worked well
for me!

After mod Frequency Range:

118.0 to 135.995(AM/FM)/ 136.00 to 174.00 MHz

320.0 to 399.995(AM/FM)/ 400.00 to 530.00 MHz

Steps:

1. Remove cover (one bolt on cover).

2. Look at the main board. Locate the main processor, under a RF shield.
Just to the right of it, among all of the diodes, you should see a vertical jumper marked W13.

3. Cut the jumper (do it on top to allow for reconstruction later if you want).

4. Reassemble to radio, and try it out!

Please email any additional mods for this rig to:

[e-mail] . Enjoy!!!!

Additional info.

In some European models RX is not extended even W13 is removed. To Extend VHF and UHF rx do the following trick:

Press and hold 4th buttons from top (both, left and right side of the display) while turning the radio on.

This modification is read 2749 times.

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05-06-1999

(IC-2800) Icom IC-2800 Extended RX/TX Mod

Date: 16-07-2000

User comment

From:

José A. Marrero

Subject: 2 more diodes installed
Some versions comming with the diodes D59 and D60 installed and it´s necessary to cut it for free RX/TX ( plus the 4 diodes

indicated for you )

Date: 30-12-2001

User comment

From:

Roy Rodgers

Subject: Cloning software
After performing this modification, the cloning software will not be compatible with the radio.

I recommend that if you plan on programming via the cloning software, before the mod clone the radio, and then perform the
mod.

I found out by calling icom, the mod turns the radio into the japanese version, and the software for that version is not
available.

This modification is read 3237 times.

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17-07-1999

(IC-2800) Icom IC-2800 Extended RX/TX Mod, Australian model

Hi all you lucky IC-2800H Owners, I have owned mine for 4 months now and have just performed the expand RX/TX mods and it
works very well indeed.
PLEASE NOTE: THE J.PEG PICTURES ATTACHED TO THIS FILE SHOW THE AUSTRALIAN MODEL RADIO, there are two diodes less
in the AUS MODEL than what is shown in the radio that is already circulating on the Internet.
Remove the large single screw that holds the only cover on, be careful when lifting this cover off with a small bladed screwdriver
because it is held quite tight with spring loaded contacts down both sides, once this is done turn radio so fan end is facing toward
you and locate CPU under tin shield at fan end and link W13 is to the right of CPU.
The two J.PEG PICTURES should be easy to follow and you can zoom and print them using PAINTSHOP PRO or COMPUPIC.

My radio will now RX 118 - 175
320 - 530
800 - 999
TX 136 - 175
400 - 479

118 - 136 is AM RX ONLY

I have not check its RX or POWER SPECS since I performed the mods but from the reports that I have had it would seem that it
works very well.
Now after the mods are finished you have to reset the CPU in a different way to that described in the instruction manual, with
the radio OFF hold down the left and right BOTTOM or fourth menu buttons and turn the radio on, it should now be reset,
expanded and ready to be programmed because all memory information will be erased.
I take no responsibility for these modifications if you stuff up but if you use a good quality soldering station and are careful it is

not a hard mod to do,..........but my next project could be a different story I also own a new IC-Q7E HANDHELD and I am going

to have a go at modifying it as well, if that is successful also I will post that on the NET and WW PACKET with pictures.

For those who maybe interested I use a SONY MAVICA FD71 digital camera .This information has been supplied by
David Spicer, VK7ZDJ
5a Helen Street,
ULVERSTONE, 7315.

Tasmania, Australia. email: [e-mail]

This modification is read 2191 times.

23-08-1999

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(IC-2800) IC-2800/HM98 tx-audio mod

From: PA3HGT@ON6AR.#AN.BEL.EU

When you own a ICOM 2800H with the HM98 mike , use this nice trx in the mobile like i do, receive sometimes complains about
the hollow modulation and pick up too many backgroundnoise ? Then maybe this is the solution too eliminate this problem.
Solder a capacitor between 10 - 47 nf paralell on the mic-element.
If you opened the HM98-mike , you can see that the audio cannot applied properly to the mike-element .
To change that , you've too drill a small hole of 1mm so that the audio is applied into the center of the mic-element.

This modification is read 2312 times.

31-10-1999

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(IC-2800) sensitivity ICOM IC-2800H

Here are some sensitivitymeasurements for the Icom IC2800H results are uV/10 db sinad.

136 Mc : 0.144 uV 400 Mc : 0.174 uV
140 Mc : 0.167 uV 405 Mc : 0.163 uV
144 Mc : 0.14 uV 410 Mc : 0.144 uV
145 Mc : 0.133 uV 415 Mc : 0.137 uV
146 Mc : 0.132 uV 420 Mc : 0.133 uV
147 Mc : 0.11 uV 425 Mc : 0.11 uV
148 Mc : 0.109 uV 430 Mc : 0.109 uV
150 Mc : 0.114 uV 431 Mc : 0.11 uV
155 Mc : 0.11 uV 432 Mc : 0.107 uV
160 Mc : 0.138 uV 433 Mc : 0.109 uV
165 Mc : 0.115 uV 434 Mc : 0.111 uV
170 Mc : 0.108 uV 435 Mc : 0.112 uV
174 Mc : 0.108 uV 436 Mc : 0.111 uV
437 Mc : 0.111 uV

----------------- 438 Mc : 0.108 uV
Fm narrow mode 439 Mc : 0.111 uV
used on 2mtrs 440 Mc : 0.133 uV
only on Europe & 441 Mc : 0.103 uV
Italy versions ! 442 Mc : 0.106 uV
144 Mc : 0.088 uV 443 Mc : 0.095 uV
145 Mc : 0.087 uV 444 Mc : 0.11 uV
146 Mc : 0.087 uV 445 Mc : 0.106 uV
147 Mc : 0.085 uV 446 Mc : 0.104 uV
148 Mc : 0.085 uV 447 Mc : 0.107 uV
448 Mc : 0.104 uV
449 Mc : 0.105 uV
450 Mc : 0.107 uV
455 Mc : 0.141 uV
460 Mc : 0.199 uV
465 Mc : 0.167 uV
470 Mc : 0.153 uV
475 Mc : 0.139 uV
480 Mc : 0.151 uV
485 Mc : 0.162 uV
490 Mc : 0.167 uV
495 Mc : 0.168 uV
500 Mc : 0.18 uV
505 Mc : 0.175 uV
510 Mc : 0.199 uV
515 Mc : 0.225 uV
520 Mc : 0.282 uV
525 Mc : 0.352 uV
530 Mc : 0.485 uV

This modification is read 2314 times.

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02-04-2000

(IC-2800) IC-2800H cross band mode operation

Author: Colin G1IVG - [e-mail]

Step #1:

Prior to the cross band mode, set the squelch delay to short or the audio for the first 3 seconds will be chopped off in your next
transmission. (Use the set-up menu shown in the manual).

Step #2:

To start the cross band mode, set the VHF and UHF frequencies you like to link together for cross band operation, (program the
splits, PL tone, etc. all in advance)

Step #3: (Main Step)

Press and hold "CHG/L" button while holding both VHF and UHF "MAIN" buttons simultaneously for few seconds until the blinking
key icon appears.

Step #4: (This is an optional step)

Set hang up time to ZERO on cross band repeat mode by pressing and holding "CHG/L" button while holding UHF "MAIN" and
bottom menu key at VHF side for few seconds. The Key lock indicator will blink, and the unit is ready to operate. (This is a direct
translation form the Japanese manual. You may omit this step or experiment with it.)

Step #5:

To disable the cross band, repeat the step #3 above until the blinking KEY icon disappears.

This modification is read 2638 times.

27-01-2001

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(IC-2800) DTMF options card

Author: 73 de SM0XKO Peter

If you have ICOM IC-2800 + options DTMF card ( CT-91 ) (in sweden UT-49) you can make changes from other radios through
DTMF tones.

First!
Push [DTMF] twice on the radio and it´s light (REMO) in the display.

To make changes press

Open = B code # default code = 000

1 = Call channel
2 = Memory
3 = VFO

6 = High transmit power
9 = Low transmit power

* = step down
# = step up

A = Escape
D = Clear only in mode 2 or 3. After that you can enter memory channel number or VFO Mhz

DB* = Log out / Cross band repeater ON
B* = Log out / Cross band repeater OFF

Good luck! / 73 de SM0XKO Peter

This modification is read 2160 times.

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20-10-2001

(IC-2800) Screen saver Turn OFF option for IC-2800

Author: Chuck Lynn - [e-mail]

When the unit is turned off, simultaneously depress the "CHANG/L" key and the "POWER" key. Both located on the bottom
corners of the control head.

Sceen saver mode will be suspended.

To reactivate sceen saver mode repeat the above step.

73
KG4FKU
Chuck

This modification is read 2132 times.

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13-01-2002

(IC-2800) Cross Band Repeat for IC-2800

Author: KC5VCF - [e-mail]

To cross band repeat with the IC2800

Hold down simutanisuly CHG/L and both MAIN/EDIT buttons.

This modification is read 1221 times.

17-02-2002

(IC-2800) Enable crossband function for IC-2800

Author: - [e-mail]

Unsolder or cut D 60 (near W 13)

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Press "Main UHF,Main VHF,Chg/L"

For 2 seconds, crossband will be enabled...

This modification is read 649 times.

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19-07-1998

(IC-281) Crossband repeat

To enable crossband repeat press and hold the BAND key and the SET key for about a second, a flashing L will appear in the
lower right. To turn off hold the SET key.
Unfortunately code squelch does not seem to work when crossband repeat is enabled. Don't know about tone squelch.

This modification is read 877 times.

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19-07-1998

(IC-281) Extended Receive for IC-281

To enable extended receive a jumper has to be removed. To enable extended transmit a diode has to be removed. I have only
tested the extended receive which gives you from 118-174.995 and 320-479.995.

Open the case by removing all the screws on the top, bottom and left/right sides and separating the top and bottom covers from
the chassis.

Next remove the plastic front panel that covers the logic circuit board by removing the two top and two bottom screws that
attach it to the chassis.

Next remove the front panel logic board by taking out the four front screws that attach it to the chassis.
Position the logic board so that the side normally near the chassis is on top and a round flat battery attached via leads is visible

with the connector near the bottom and the cut out at the bottom right.
Below the battery on the lower right there are a number of diodes, most likely surfaced mounted. Look just to the left of the

diodes, there will be a very small surface mount jumper at the bottom (-#WW#- on diagram below). There is no silk screen on
the board to identify it (on mine at least) but the part itself may have a zero printed on it for zero ohms. Removing this jumper
will give you extended receive capability.

Diagram (very bad but hopefully you get the idea)

R O U N D
B A T T E R Y

! ! ! ! !
! # # # # -#D#­ D D D D -#D#- -#D#
# # # # ! -#D#- -#D#-

-#WW#- ! ! ! ! -#D#- -***-

This modification is read 932 times.

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19-07-1998

(IC-281) Extended Transmit for IC-281

By removing one of the diodes in the area mentioned above extended transmit is purported to be possible. I have not verified
this since I don't need this capability but it is supposed to significantly extend the transmit capability in the VHF band.

To enable extended transmit remove the diode that is most near the right hand bottom part of the board as indicated in the
diagram above with -***-.

Reassemble and reset CPU per instruction manual.
Note:When you reset the CPU you loose all memory and have too re-program all.

This modification is read 899 times.

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19-07-1998

(IC-2AT) Coverage IC-2AT 140-150 MHz

If you have studied the schematic diagram for this radio, you will notice that pins 15 and 16 are not indicated on the
programmable divider chip IC1 (TC9122).
By simply connecting pin 15 thru a switch to pin 1, you will be able to move the radio up in frequency by 10 MHZ.

Some of these radios were sold without covering 140-150 MHZ.
The modification for this extended coverage is described below:

1. Open up the radio and locate the FLEXIBLE BOARD, this connects the thumbwheel switches to the MAIN BOARD.

2. At the MAIN BOARD end of the FLEXIBLE BOARD, add a jumper at location C4. There should already be a jumper at location
C2.

3. At the thumbwheel switch end of the FLEXIBLE BOARD, remove the jumper which connects C3 and COM.

4. Reassemble the radio. Coverage is now 140-150 MHZ.(MARS/CAP)

Now, if you activate the switch described above, the radio will now operate in the 150-160 MHZ range, after L3 adjustment,
described below.

This modification is read 1054 times.

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19-07-1998

(IC-2AT) Operation and L3 ADJUSTMENT

1. Activate switch and dial up a known active frequency.

2. Adjust L3 until PLL locks up and radio begins receiving.
(you need an active frequency to tell when this happens)

3. To return to 140-150 MHZ, repeat above steps with switch off.

Notes and disclaimer

1. Drill a hole in the case of the radio so that L3 can be adjusted from outside of the radio.

2. The above information is presented for educational purposes only, and is not an endorsement of any particular practice.

3. This MOD has been in operation for 6 years with no ill effects on the radio

4. This MOD courtesy N2MOD.

This modification is read 885 times.

19-07-1998

(IC-2GAT) Out-of-band transmit mod for IC-2GAT handheld 2M transceiver

Back side of display board:
_____________________________________
I D505
I D507 D504 ___
I ___ ___ I___I I
I I___I I___I -- + -­I D506 Q506 . . I I
I _o_------ _o_ J I hole for
I I___I I I___I . I on/off-vol
I o o I o o I control
I I I I__________________
I -----K---------- I
I add diode: 1N914 or equiv. I
I I

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Connect diode between top lead of D506 and lower right lead of Q506 as shown.
A surface mount diode may be added right of Q506 at J. note that the .___. are the same trace, while above the J is the center

pole.o

. Note that this diode is 1906-0336, "-" at bottom, both "+" at top.
___|___
^ ^
| |
. .

Notes:
D506 may be absent. If not, remove it.
Reset CPU if needed.

A friend did this and his IC-2GAT can now transmit 138 to 178 MHz (no RF power output measurements were made). He did no
retuning, and did not have to reset the CPU. He used a tiny axial-lead glass diode, replaced its leads with wire-wrap wire, and

encased it in shrink-tube. The operation requires a super-tiny soldering iron. Observe CMOS soldering precautions: Unplug the
iron and ground the tip before touching the circuit.

The 2GAT mod is really...
Remove D 504 which is orginally a 1SS196 and replace it with a 1SS184 which is a dual diode. The service manual componet
symbol shows the dual diode but lists the 196.

This modification is read 982 times.

19-07-1998

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(IC-2GAT) Step mods for IC-2GAT

To RESET the CPU (and wipe out memory), hold the LIGHT button AND the FUNCTION button while CPU is on, then turn it off,
wait a second, and turn it back on. Continue holding the buttons while all the LCD segments display until "46.01" shows (about 1­2 seconds). This puts the radio into 5/10/15/20/25 khz step mode. Its starts in 15 khz steps and other steps in the list may be
chosen. I wish 30 khz were in the list.

The instructions for the IC-2GE are similar except that you hold down LIGHT and the WR button on top right next to the power
switch. The IC-2GAT also performs this same reset, and also enters the 12.5/25 khz step mode. The step starts at 25 khz. When
it is set to 12.5 (the only other choice until you reset the CPU the first way) you can dial up frequencies like 146.0125 which
shows like "46.0125" where the "25" are BOTH smaller digits. The "5" never shows in the "American mode". The display goes to
"46.01" in the "American mode" and to "46.00" in the European mode.

Another curiosity is that when I RESET my CPU, I did so while it was tuned to 162.55 (weather). When I turned the power back
on, EVERY segment was displayed, but the radio was actually receiving 162.55 anyway. Then when the reset finally took effect,
the display went to "46.01" and the weather signal was lost. I also notice that sometimes, the "U" for synthesizer unlock (in the
10's position of the memory number) shows up just at the moment the "46.01" or "46.00" does, then ends in a second. I guess
the sythesizer is being reset as well.

This modification is read 834 times.

19-07-1998

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(IC-2GAT) IC-2GAT to packet

For those of you who are trying to interface something to a rig which has a single two-conductor plug for both microphone input
and push-to-talk connections, such as many of the handheld rigs including the Icom IC-2AT and IC-02AT, here are three circuits
that may be useful to you:

::: Electret condenser microphone to radio:
Radio Shack #270-092 mic element?

MIC--------------+--------------------O------------> Mic/PTT on radio
| | |
| | | <-- Shield
+------///----+ |
| (20-30K) / <-- PTT |
| / switch |
+--------------------+ +-----------+------------> Ground on radio

::: Dynamic microphone to radio:

MIC +-----------------------O----------> Mic/PTT on radio
COIL C |
C |
C / | <-- Shield
| / |
+-----------+ +-------+----------> Ground on radio

::: High-level input (such as from tape recorder, RTTY AFSK generator,
or Packet TNC output) to radio:

HIGH LEVEL OUTPUT: RADIO INPUT:
(0.47 uf)
Audio to transmitter -------||-------+----O------> Mic/PTT on radio
(25K) | |
Push-to-talk -------///------------+ | <-- Shield

|
Ground -----------------------------------+------> Ground on radio

I made a big mistake in the previously-posted schematic of the connection between an Icom IC-2A, 2AT, or 02AT and a packet
radio TNC, RTTY afsk unit, or another microphone. The resistor and capacitor were backwards. The correct schematic follows:

Audio
from TNC* PTT Ground
| | |

--- / |
(C1) --- (R1) |
| / |
| | |
Icom HT | | |
mic input------+-------------+ |
|
ground--------------------------------+

C1 - 0.47 uf capacitor
R1 - 25K resistor

* TNC or RTTY afsk or another microphone or whatever you are interfacing to your Icom HT.

This modification is read 780 times.

19-07-1998

(IC-2GAT) ICOM IC-A20 alkaline headset-adapter lost-in-the-soup

[e-mail] (Sir Matthew G. Dralle)

> > ...I paid $449 + sales tax for a new IC-A20, $26 for the ICOM
> >alkaline battery pack, and $50 (arrgghhh) for the headset adapter
> >(Sigtronics, with a yoke mounted PTT switch). If you can find
> >the aviation-standard connectors, it would be easy to fabricate
> >a headset adaptor and save a few dollars...

> Be careful - There is a LOT more to the ICOM PTT switch than meets the eye.
> There is no easy way to match up an external mic and the ICOM with out the
> PTT unit from ICOM. A couple of jacks and a switch or two isn't gonna do it.
> Icom uses a wierd wiring scheem in the mic jack so that if you were to plug
> a mic into the Icom directly, you would have to use the PTT *ON* the radio. I

.....[ stuff deleted some where in here ]

> can't remember the exact wiring now, but without extensive modification and
> an additional relay *ADDED* to the PTT cicuit from Icom, you won't be able to
> use your standard PTT that you got with your headphones. I hate to be a
> downer, but those are the facts...
>
> Matt Dralle
> Serious RV-4 Builder...
> [e-mail]

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Hi, I have been reading this news group for about 5 years now but this is my first post. Sorry if anything gets screwed up with
the post.

First, I would like to say thanks to all the knowledgable people who have shared their experiences ( the list of names is to long ).
Please keep up the GOOD work !!

As to the ICOM question of PPTs.
I have just finished installing an ICOM in my RANS S-10 with PTTs on the throttle with a Sigtronics intercom.
This is how I made every thing play together. Sorry for the poor graphics.
ICOM mic plug tip to one side of a normally open push button switch. Other side of switch to middle ring of a standard mic jack.

Carry the shield straight from the mic plug sleve to the standard mic jack sleve. Now you can plug either a headset mic or the
mic plug from the Sigtronic intercom into it.

___T___

push button
switch ^ ^
| |
____________________| |_____________________________
| |___
C IIIII V
| n. c. --^ _]
|_____________________________________________________|
mic plug shield standard mic jack
for ICOM

OR
ICOM mic plug tip to the middle ring of a standard mic jack. Carry the shield straight from the mic plug sleve to the standard mic

jack sleve. Now you can put a DC PPT in the standard mic jack and then put either a headset mic or the mic plug from the
Sigtronic intercom into the PPT mic jack. NOTE that if you plug a mic or the intercom mic plug into this it will key the ICOM.

______________________________________
| |___
C IIIII V
| n. c. --^ _]
|_____________________________________|
mic plug standard mic jack
for ICOM

Standard aircraft radios use the tip to shield to key the transmitter, the ICOM does NOT use this method.
David Clock PPT switch switches BOTH the mic lead AND the tx key lead, I think some others do as well.
Jim Needham N201S

-----------------------------------------------------------------------­When I wanted to do this, I started out by making two simple straight through adapters, one for the mic and one for the phone.

Then I measured all combinations trying to figure out how ICOM did thier trick. I accidently shorted the mic tip to shield and the
tx LCD lit. I also pluged a mic from a headset and noticed that the tx keyed, and having another radio on the bench, heard the
feedback.

ICOM mic jack, only 2 conductor
tip to shield, about 4 or 5 volts
phone jack
rx, audio from tip to shield
tx, same DC as above from tip to shield

My installation does work. In the air, on the ground, upside down B-{)### I have also talked to someone else in my plane from
another ICOM and it sonded good to me.

Hope you have the same good luck that I have had. Stay out of the trees.
Jim Needham N201S

This modification is read 804 times.

27-03-2000

(IC-2GXAT) The ICOM 2GXAT HARDWARE MOD

1. Open the radio by following the manuals instructions.

2. On the half with the display and tone keys find the big chip (logic chip)

3. To the right of it there are some small parts that look like this:

|--------|
| Logic | XX XX
| Chip | x
| |D14----> x XX
| | x x
|--------| XX XX XX<-D13

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4. Remove both d13 (rx) and d14 (tx) and close the radio back up!

5. Reset the CPU and you're done!

6. If you mess up your radio I take NO RESPONSIBILITY. You do this at your own risk.

If anything you'll break the back light as most people do... But to help not do this the transistor d14 DOES NOT LOOK LIKE
d13!!!

This modification is read 757 times.

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06-03-2002

(IC-2GXAT) Software mod, to open IC-2GXAT

Author: - [e-mail]

This is a software mod to open up the receiver for the IC-2GXAT.

(YOU DO NOT NEED TO EVEN TAKE THE RADIO APART!)

1. Turn off the radio.

2. Press and hold the, F KEY, Scan and Dup keys.

3. While holding all 3 keys turn on the radio, continue to hold the keys for about 3 seconds WAITING until the display returns
to normal before releasing the keys.

I did this to my HT and it receives from 50Mhz – 204Mhz.

This modification is read 188 times.

19-07-1998

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(IC-2IA) IC-2Ia mic mods

Hello folks...I bought an ic-2Ia last week for use by my xyl kb8czl. I chose this particular ht for its simplicity of operation (after
initial setup).

However, it didn't take long before we began receiving poor xmit audio reports. It was described as "muffled and constricted ­like talking thru a garden hose".
As it turns out the design engineers at icom left no provision to get the melodious tones of your voice to the microphone except
to go thru the plastic case.

After i noticed this problem, i returned the radio to my dealer and tried several others. They all sounded the same. Then the
salesman called icom service-they admitted they knew of the problem and recommended a hole be drilled in front of the mic.

Heres how to do it - proceed carefully-

1. Shut off radio

2. Remove battery pack

3. Remove 4 phillips head screws from rear of case

4. Carefully pull off front of case

5. Gently remove mic element from rubber holder

6. Unscrew 4 phillips head screws retaining speaker

7. Support case on soft surface

8. Drill hole thru center of mic rubber from inside - i used 5/64 inch (2mm) drill

9. Reassemble in reverse order

10. Marvel at fb audio

11. Thats it, folks...Hope you like your new ht as much as we do...73, ART-K8CIT..

This modification is read 584 times.

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19-07-1998

(IC-2IA) IC-2IA lousey xmit audio fix

From: K8CIT@N8NNN.#SEMI.MI.USA.NA

Hello folks...i bought an IC-2IA last week for use by my xyl KB8CZL. I chose this particular ht for its simplicity of operation (after
initial setup). However, it didn't take long before we began receiving poor xmit audio reports.
It was described as "muffled and constricted - like talking thru a garden hose"

As it turns out the design engineers at icom left no provision to get the melodious tones of your voice to the microphone except
to go thru the plastic case.

After i noticed this problem, i returned the radio to my dealer and tried several others. They all sounded the same. Then the
salesman called icom service-they admitted they knew of the problem and recommended a hole be drilled in front of the mic.

Heres how to do it - proceed carefully-

1. Shut off radio

2. Remove battery pack

3. Remove 4 phillips head screws from rear of case

4. Carefully pull off front of case

5. Gently remove mic element from rubber holder

6. Unscrew 4 phillips head screws retaining speaker

7. Support case on soft surface

8. Drill hole thru center of mic rubber from inside - i used 5/64 inch (2mm) drill

9. Reassemble in reverse order

10. Marvel at FB audio

This modification is read 560 times.

05-10-2000

(IC-2IA) IC-2IA mod.

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Author: D.C. - [e-mail]

This quick mod to open the RX only with aircraft it also tune much more but not as good like 220mhz..

Same mod as the ic-2sat hold all buttons but (S) and turn on that's it!

I had tried it and showed Icom and the local dealer who tested it.. they where amazed!!
See ya & 73s, D C

This modification is read 591 times.

19-07-1998

(IC-2SAT) IC-2SAT out-of-band transmit mod

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● Remove the back cover as per instuctions on page 34 of your manual.

● o

------------­ : / :
: / :

------------­ o o

● as indicated by the drawing one diode has to be added to complete the modification

● Beside the lower right corner of the Main IC, there are 3 chip resistors. Just to the right of the resistors, you can see 3 silk

screened dots surrounded by a portion of a rectangle where a factory diode package would have been. The new diode
(1N914 or whatever you care to use) is placed with the cathode (band) to the top dot and anode to the lower left dot.

● This completes the mod. The HT will now transmit throughout the 150-160 MHz range.

I have completed this mod and on my 2SAT and it and it works well. The components are very small and the soldering has to be
precise, BE CAREFUL!!!

This modification is read 1129 times.

19-07-1998

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(IC-2SAT) Icom IC-2SAT enhancements

A friend of mine in Germany mailed me a *very* intriguing photocopy of a letter he received from someone who works for Icom­Europe. It's an internal ICOM memo with details on how to do all sorts of nifty tricks with the IC-2SE (which may nicely translate
to IC-2SAT tricks).

I have attempted to exactly duplicate the memo below, mangled spelling, unclear passages, and all. I don't have an IC-2SAT
service manual yet, and so I'm not qualified to say if this is all really applicable or not. And, the German at the closing is a
mystery. I typed "fu:r" to indicate "fr". Anyone with more details, please let us know!

Bob Cromwell KC9RG
[e-mail]

ps:
For the people asking "what was your original diode matrix, that appears at the end. There was some thought that the matrix
programming changed after the first few (hundred? thousand?) models. This is from the schematic that came with mine, with
serial number in the 9500's.

pps:

Before you ask "where's part 1", that was the article titled "Icom IC-2SAT", where I gave results of signal generator testing....

ICOM (Europe) GmbH
Himmelgeister Strasse 100
4000 Du:sseldorf 1
F. R. Germany
Phone: 0211 / 34 60 47
Fax: 0211 / 33 36 39
Telex: 8588082 ICOM D
To: Icom Dealer
Dusseldorf, 14.4.89

I C O M S E R V I C E I N F O R M A T I O N I C - 2 S E

Push Key + switch on Requested Mode Remark
LIGHT + MON CPU RESET Clear all Memories
LIGHT + FUNC FULL DISPLAY Display Func Test

---------------------------------------------------------------------------­LIGHT + V/M SIMPLE MODE Info on Equipment
LIGHT + C (SCAN) MULTI-FUNCTION MODE Details in Handb.

---------------------------------------------------------------------------­LIGHT + FUNC + V/M RECEIVER MODE (All Band) All Band - no Tx

----------------------------------------------------------------------------

1. Start SIMPLE MODE TRANSCEIVER MODE/ Tx only HAM-Band/

2. Light + FUNC + C multi-function mode Rx see list below

---------------------------------------------------------------------------­Extent Transmitter Install Diode AD (D6) Tx: 139-163 MHz (FM)

Manual AM/FM Mode Change all Bands: Rx Band Ranges:

1. Change to RECEIVER MODE (not receive mode) 75 - 106 MHz (FM)

2. FUNC + PTT (working in RECEIVER MODE) 108 - 130 MHz (AM)
138 - 169 MHz (FM)
Note: (+) 174 - 192 MHz (FM)

1. keep pushing each key at same time, 204 - 243 MHz (FM)

2. switch on equipment, 250 - 291 MHz (FM)

3. hold (about 4sec.) until "SET" appear, 310 - 370 MHz (FM)

4. release keys and requested mode appear;

Easily tunning step change (5 - 50 KHz):

1. push and hold FUNC key for 2sec.

2. rotate TUNING CONTROL.

3. Push FUNC to return to previous mode.

Frequency ranges are appoximately and not garantied. Receiver sensitivity garantied only in HAM-Band (144 - 146 MHz).
In RECEIVER Mode equipment running exclusively as a Receiver, cannot transmit at all.
Achtung:

nur fu:r den Fachha:ndler zum Zwecke des Service bestimmt. Es mu:ssen die Bestimmungen des Fernmelde-Anlagengesetz
heachtet werden.

This modification is read 1063 times.

19-07-1998

(IC-2SAT) IC-2SA/E Frequency range expantion

● Remove any diode position on D6

● Install diode DA (code No. 1750000160) position D6

After this modification frequency lock range will be expand typicaly :

RX (MHz) : 108 - 140 (AM) , 138-169 (FM) , 310-370 (FM) ,
TX (MHz) : 139 - 163 (FM) ,

------------------------------------------------­ | |
| |
| |
| |
| R R |
| 3 3 |
| 9 8 |
| o |
| R R R ### <--- |
| 4 4 4 ### |
| 1 2 3 o o R |
| 6 |
| ___________ 1 |
| / |
| / |
| | SP1 | |
| | | |
| | | |
| / |
| \___________/ |
| |

-------------------------------------------------

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Yeah, the above is crude, just meant to give the relative locations of the mysterious diode, SP1, R38, R39, R41, R42, R43, and
R61. The 3-terminal box with an arrow drawn to it (the arrow is in the original image) looks like the below. A diode is connected
from the lower left tab to the upper tab.

___
| |

-------------------­ | / |
| --- |
| /_ |
| ____| |
| / |
| | |

-------------------­ | | | |

--- ---

diode matrix programming
To simplify/fool-proof this, if the schematic has:
(X) --->|--- (Y)

I'll say "from X to Y". From the "IC-2SAT IC-2SET SCHEMATIC DIAGRAM":

Japan Version D6: DA115 from KEYI2 to KEYS2
Europe Version D5: DA115 from KEYI0 to KEYS3
D6: DA115 from KEYI2 to KEYS2
Italy Version D5: DAN202U from KEYI1 to KEYS3 and
from KEYI0 to KEYS3
D6: DA114 from KEYI0 to KEYS2
U.S.A. Version D4: DA115 from KEYI2 to KEYS3
D9: ISS254 from KEYI1 to KEYS2
Australia Version D5: DA114 from KEYI1 to KEYS3
D6: DA115 from KEYI2 to KEYS2
Asia Version D4: DA115 from KEYI2 to KEYS3

Now, can anyone use this to figure out the Icom-Europe memo???

Bob KC9RG

[e-mail]

This modification is read 1054 times.

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19-07-1998

(IC-2SAT) Icom IC-2SAT unpublished Specificatons

I have access to some test equipment at work and did some studies on this little marvel of a transceiver. Here are some of my
studies I have found so far:

12 dB SINAD Receiver Sensitivity:

Frequency: µV dBm

80.00 MHz 217 -60

90.00 MHz 64 -70

100.0 MHz 18 -82

110.0 MHz 2 -101

140.0 MHz .185 -122

150.0 MHz .16 -123

160.0 MHz .3 -117

170.0 MHz .9 -108

180.0 MHz 17 -82

190.0 MHz 74 -74

191.61MHz --- vfo goes unlocked ---

210.0 MHz 590 -50

220.0 MHz 590 -50

230.0 MHz 2000 -40

250.0 MHz 173 -62

260.0 MHz 340 -56

270.0 MHz 27 -78

280.0 MHz 4 -94

290.0 MHz .7 -110

300.0 MHz .38 -115

310.0 MHz .5 -113

320.0 MHz .275 -118

330.0 MHz .23 -120

340.0 MHz .23 -120

350.0 MHz .32 -117

360.0 MHz .4 -115

365.0 MHz .72 -110

-------------------------------vfo goes unlocked-------------------

Transmit Power: Voltage input at Coaxial plug on top of radio versus Power output

15.0V 5.3W

14.0V 5.2W