Vertex Standard VX-420 User Manual
UHF FM Transceiver
VX-410/-420 series
Service Manual
©2004 VERTEX STANDARD CO., LTD. EC050U90A
VERTEX STANDARD CO., LTD.
4-8-8 Nakameguro, Meguro-Ku, Tokyo 153-8644, Japan
VERTEX STANDARD
US Headquarters
10900 Walker Street, Cypress, CA 90630, U.S.A.
YAESU EUROPE B.V.
P.O. Box 75525, 1118 ZN Schiphol, The Netherlands
YAESU UK LTD.
Unit 12, Sun Valley Business Park, Winnall Close
Winchester, Hampshire, SO23 0LB, U.K.
VERTEX STANDARD HK LTD.
Unit 5, 20/F., Seaview Centre, 139-141 Hoi Bun Road,
Kwun Tong, Kowloon, Hong Kong
VX-410 series VX-420 series
Introduction
This manual provides technical information necessary for servicing the VX-410/-420 series FM Transceiver.
Servicing this equipment requires expertise in handling surface-mount chip components. Attempts by non-qualified
persons to service this equipment may result in permanent damage not covered by the warranty, and may be illegal in
some countries.
Two PCB layout diagrams are provided for each double-sided circuit board in the transceiver. Each side of is referred
to by the type of the majority of components installed on that side (“leaded” or “chip-only”). In most cases one side has
only chip components, and the other has either a mixture of both chip and leaded components (trimmers, coils, electrolytic
capacitors, ICs, etc.), or leaded components only.
While we believe the technical information in this manual to be correct, VERTEX STANDARD assumes no liability
for damage that may occur as a result of typographical or other errors that may be present. Your cooperation in pointing
out any inconsistencies in the technical information would be appreciated.
Contents
Operating Manual Reprint ................................... 2
Cloning...............................................................................
Specifications .......................................................... 8
Exploded View & Miscellaneous Parts .............. 9
Block Diagram .......................................................11
Circuit Description ..............................................13
Alignment .............................................................. 15
7
Board Unit (
MAIN Unit ............................................................... 19
DUMMY Unit .......................................................... 34
Optional Units (
FVP-25 Encryption / DTMF Pager Unit .............. 35
VTP-50 VX-Trunk Unit .......................................... 37
DVS-5 Voice Storage Unit ..................................... 39
Schematics, Layouts & Parts
Schematics, Layouts & Parts
)
)
Operating Manual Reprint
Controls & Connectors Before You Begin
LED Indicator
Glows Green Monitor on (
Blinking Green Busy Channel (or SQL off)
Glows Red Transmitting
Blinking Red Battery Voltage is low
Yellow Receiving a Selective Call
Antenna
Push To Talk
(
PTT) Switch
Microphone
Side 1 Switch
Side 2 Switch
LCD (VX-420 series)
or Side 1, 2 switch is activated : VX-410 series only
CH (Channel) Selector
VOL/PWR Knob
MIC/SP Jack
(
External Mic/Earphone
Speaker
16 KEY (VX-420 series)
Battery Pack Latch
Display Icons & Indicators (VX-420 Only)
: “Scan” is activated
: “Priority Scan” is activated
“Call” indicator
Receiver Monitor
)
Battery Pack Installation and Removal
Ì To install the battery, hold the transceiver with your
left hand, so your palm is over the speaker and your
thumb is on the top of the belt clip. Insert the battery
pack into the battery compartment on the back of the
radio while tilting the Belt Clip outward, then close
the Battery Pack Latch until it locks in place with a
“Click.”
)
Tilt the Belt Clip
Insert the Battery Pack
Close the Battery Pack Latch
Ì To remove the battery, turn the radio off and remove
any protective cases. Open the Battery Pack latch on
the bottom of the radio, then slide the battery downward and out from the radio while holding the Belt
Clip.
Caution!
Do not attempt to open any of the rechargeable NiCd packs, as they could explode if accidentally shortcircuited.
“Dual Watch” is activated
“Encryption” is enabled
8 Character Alpha-numeric Display
Low Transmit Power Mode “ON”
“Talk-Around” is enabled
“Voice Message” received
Group “A”
Group “B”
Priority Channel
Low Battery Indication
Ì As the battery discharges during use, the voltage gradu-
ally becomes lower. When the battery voltage becomes
to low, substitute a freshly charged battery and recharge
the depleted pack. The TX/BUSY indicator on the top
of the radio will blink red when the battery voltage is
low.
Ì Avoid recharging Ni-Cd batteries often with little use
between charges, as this can degrade the charge capacity. We recommend that you carry an extra, fullycharged pack with you so the operational battery may
be used until depletion (this “deep cycling” technique
promotes better long-term battery capacity).
2
Operation
Operating Manual Reprint
Preliminary Steps
Ì Install a charged battery pack onto the transceiver, as
described previously.
Ì Screw the supplied antenna onto the Antenna jack.
Never attempt to operate this transceiver without an
antenna connected.
Ì If you have a Speaker/Microphone, we recommend that
it not be connected until you are familiar with the ba-
sic operation of the VX-410/-420.
Operation Quick Start
Ì Turn the top panel’s VOL/
PWR knob clockwise to turn
on the radio on.
Ì Turn the top panel’s CH selec-
tor knob to choose the desired
operating channel.
Ì Rotate the VOL/PWR knob to
set the volume level. If no sig-
nal is present, press and hold
in the Soft key assigned to
“MONITOR” for more than 1
seconds; background noise will
now be heard, and you may use this to set the VOL/
PWR knob for the desired audio level.
Ì Press and hold in the Soft key
assigned to “MONITOR” for
more than 1 seconds (or press
the MONITOR key twice) to
quiet the noise and resume normal (quiet) monitoring.
Ì To transmit, monitor the chan-
nel and make sure it is clear.
THIS IS AN FCC REQUIRMENT!
Ì To transmit, press and hold in
the PTT switch. Speak into the
microphone area of the front
panel grille (lower left-hand
corner) in a normal voice level. To return to the Receive mode, release the PTT switch.
Ì If a Speaker/Microphone is available, remove the plas-
tic cap and its two mounting screws from the right side
of the transceiver, then insert the plug from the Speaker/
Microphone into the MIC/SP jack; secure the plug using the screws supplied with the Speaker/Microphone.
Hold the speaker grille up next to your ear while receiving. To transmit, press the PTT switch on the
Speaker/Microphone, just as you would on the main
transceiver’s body.
Note:Save the original plastic cap and its mounting
screws. They should be re-installed when not using the Speaker/Microphone.
Accessories & Options
FNB-64 7.2 V 700 mAh Ni-Cd Battery
FNB-V57 7.2 V 1100 mAh Ni-Cd Battery
FNB-V57IS Intrinsically-Safe 7.2 V 1100 mAh Ni-Cd Battery
FNB-V67LI 7.4 V 1600 mAh Lithium-Ion Battery
FBA-25 Alkaline Battery Case
NC-77C 220-240 VAC Overnight Desktop Charger
NC-77U 230 VAC Overnight Desktop Charger
VAC-800 Desktop Rapid Charger (for FNB-64/-V57/-V57IS)
VAC-810 Desktop Rapid Charger (for FNB-V67LI)
VAC-6800 6-unit Multi Charger
MH-45
MH-37
VC-25 VOX Headset
VCM-1 Mobile Mounting Bracket (for VAC-800/-810)
CT-42 PC Programming Cable
CT-27 Radio to Radio Programming Cable
CE64 Programming Software
VTP-50 VX-Trunk Unit
FVP-25 Encryption/DTMF pager Unit
FVP-35 Encryption Unit (Rolling code voice scrambler)
DVS-5 Voice Storage Unit
MDC1200 Digital ANI encoder Unit
B4B
A4B
Speaker/Microphone
Earpiece Microphone
3
Operating Manual Reprint
Key Function
The VX-420 series provides programmable [A], [B],
[C]
, and [D] function keys, and both the
and
series provide programmable and
switchs. These “Soft” keys functions can be customized
(set to other functions), via programming by your VER-
TEX STANDARD dealer, to meet your communications/
network requirements. Some features may require the purchase and installation of optional internal accessories. The
possible Soft key programming features are illustrated
below, and their functions are explained in the next chapter. For further details, contact your VERTEX STAN-
DARD dealer.
For future reference, check the box next to each func-
tion that has been assigned to the Soft key on your particular radio, and keep it handy.
Function
Monitor / / / / / /
Squelch Off / / / / / /
Low Power / / / / / /
Lock //// / /
Lamp //// / /
Channel Up //// / /
Channel Down //// / /
Scan / / / / / /
Follow-Me Scan / / / / / /
Dual Watch / / / / / /
Talkaround / / / / / /
Add/Del //// / /
Reset / / / / / /
Speed Dial / / / / / /
Tx Save Off / / / / / /
Call 1 / / / / / /
Call 2 / / / / / /
Call 3 / / / / / /
Code Select //// / /
Code Up //// / /
Code Down //// / /
Emergency
Group / / / / / /
ACC 1 / / / / / /
ACC 2 / / / / / /
Play / / / / / /
Record / / / / / /
Encryption / / / / / /
Soft Key (Press / Press and Hold)
[A][B][C][D]
–
–
–
/
/
–
/
Side 1 Side 2
–
/
4
/
series
–
/
Description of Operating Functions
Monitor
Press (or Press and hold) the assigned Soft key
momentarily to disable the Tone squelch.
Squelch Off
Press (or Press and hold) the assigned Soft key to
disable the Noise and Tone squelch. Again press (or
Press and hold) the assigned Soft key to resume
normal (quiet) Noise and Tone squelch action.
Low Power
Press (or Press and hold) the assigned Soft key to
set the radio’s transmitter to the “Low Power” mode,
thus extending battery life. Press (or Press and hold)
the assigned Soft key again to return to “High Power” operation when in difficult terrain.
When the radio’s transmitter is set to “Low Pow-
er” mode, the “Low” icon will be indcated on the
display.
Lock
Press (or Press and hold) the assigned Soft key to
lock the Soft keys (except Lock key); thus, the [A],
[B], [C], and [D] keys can be disabled to prevent radio settings from being disturbed.
Lamp
Press (or Press and hold) the assigned Soft key to
illuminate the LCD for five seconds.
Channel Up
Press (or Press and hold) the assigned Soft key to
switch to a higher operating channel number.
Channel Down
Press (or Press and hold) the assigned Soft key to
switch to a lower operating channel number.
Scan
The Scanning feature is used to monitor multiple
channels programmed into the transceiver. While
scanning, the radio will check each channel for the
presence of a signal, and will stop on a channel if a
signal is present.
Ì To activate scanning:
Press (or Press and hold) the assigned Soft key.
The scanner will search the channels, looking for active ones; it will pause each time it finds a channel on
which someone is speaking.
Ì To stop scanning:
Press (or Press and hold) the assigned Soft key.
Operation will revert to the channel to which the CH
knob is set.
Operating Manual Reprint
Description of Operating Functions
Follow-Me Scan
“Follow-Me” Scan feature checks a User-assigned
Priority Channel regularly as you scan the other
channels. Thus, if only Channels 1, 3, and 5 (of the 8
available channels) are designated for “Scanning,”
the user may nonetheless assign Channel as the
“User-assigned” Priority Channel via the “FollowMe” feature.
Press the assigned Soft key to activate “Follow-
Me” scanning, then turn the CH selector knob to the
channel which you want to designate as the “UserAssigned Priority Channel”. When the scanner stops
on an “active” channel, the User-assigned Priority
Channel will automatically be checked every few
seconds
.
Dual Watch
The Dual Watch feature is similar to the Scan feature, except that only two channels are monitored:
the current operating channel, and the “Priority”
channel.
Ì To activate Dual Watch:
Press (or Press and hold) the assigned Soft key.
The scanner will search the two channels; it will pause
each time it finds a channel on which someone is speak-
ing.
Ì To stop Dual Watch:
Press (or Press and hold) the assigned Soft key.
Operation will revert to the channel to which the CH
knob is set.
Talk Around
Press (or Press and hold) the assigned Soft key to
activate the Talk Around feature when you are operating on duplex channel systems (separate receive
and transmit frequencies, utilizing a “repeater” station). The Talk Around feature allows you to bypass
the repeater station and talk directly to a station that
is nearby. This feature has no effect when you are
operating on “Simplex” channels, where the receive
and transmit frequencies are already the same.
When the “TA” function is activated, the “
will be indcated on the display.
Note that your dealer may have made provision
for “Talk Around” channels by programming “repeater” and “Talk Around” frequencies on two adjacent channels. If so, the key may be used for one of
the other Pre-Programmed Functions
.
” icon
Add/Del
The Add/Del feature allows the user to arrange a
custom Scan.
Press (or Press and hold) the assigned Soft key to
delete/restore the current channel to/from your scanning list.
When you delete a current channel, “-SKIP-” will
appear on the LCD for one second after pressing the
Soft key. When you restore a current channel, “-STOP-
” will appear on the LCD for one second after press-
ing the Soft key
.
Speed Dial
Your Dealer may have pre-programmed Auto-
Dial telephone number memories into your radio.
To dial a number, just press (or Press and hold)
the Dealer-assigned Soft key for Speed Dialing. The
DTMF tones sent during the dialing sequence will
be heard in the speaker
.
TX Save Off
Press (or Press and hold) the assigned Soft key to
disable the Transmit Battery Saver, if you are operating in a location where high power is almost always needed.
The Transmit Battery Saver helps extend battery
life by reducing transmit power when a very strong
signal from an apparently nearby station is being
received. Under some circumstances, though, your
hand-held radio may not be heard well at the other
end of the communication path, and high power may
be necessary at all times
.
Call 1, 2, 3/Reset
When the 2-tone or 5-Tone selective calling unit
is installed, press (or Press and hold) the assigned
Soft key to silence the receiver and reset for another
call, when a communication is finished
.
Code Select
Press (or Press and hold) the assigned Soft key to
enable the changing the 5-Tone Paging code which
is recalled by the “Call 1” key
.
Code Up, Down
Press (or Press and hold) the assigned Soft key to
switch to a higher (or lower) paging code number
for the 5-Tone Paging System
.
5
Operating Manual Reprint
Description of Operating Functions
Emergency
The VX-410/-420 series includes an “Emergency”
feature, which may be useful, if you have someone
monitoring on the same frequency as your transceiver’s channel. For further details contact your VER-
TEX STANDARD dealer
Group
Press (or Press and hold) the assigned Soft key to
select a “A” or “B” group of channels.
Once the desired Group is reached, rotate the CH
knob to select the desired channel within the select-
ed Group
.
ACC 1, 2
When the optional unit is installed, these functions are various uses.
For further details, contact your VERTEX STAN-
DARD dealer
.
REC/PLAY (Voice Storage: Option)
This function, which requires the optional Voice
Storage Unit, Allows you to record and play back
incoming receiver audio.
Recording:
Press (or Press and hold) the assigned Soft key to
toggle the recording feature “on” and “off.” If the
incoming signal is being heard through the speaker
when the recording feature is set to “on,” the received
audio will be recorded. The last 2 minutes of incoming audio will be stored on a first-in, first-out basis.
Playback:
Press (or Press and hold) the assigned Soft key to
start playback. During playback, pressing then “#”
key lets you jump forward 8 seconds, while pressing the “” key lets you go back 8 seconds. To stop
playback before the stored message is complete,
press (or Press and hold) the assigned Soft key
.
.
ARTS (Auto Rande Transpond System : VX-420 only)
This system is designed to inform you when you
and another ARTS-equipped station are within communication range.
During ARTS operation, your radio automatical-
ly transmits for about 1 second every 55 seconds in
an attempt to shake hands with the other station.
If you have out of range for more than two minutes, your radio senses that no signal has been receives, a ringing beeper will sound, and “IN RANGE”
will appear on the LCD. If you subsequently move
back into range, as soon as the other station transmits, your beeper will sound and “OUT RANGE” will
appear on the LCD.
DTMF Paging System (VX-420 only)
This system allows paging and selective calling,
using DTMF tone sequences.
When your radio is paged by a station bearing a
tone sequence which matches yours, your radio’s
squelch will open and the alert will sound. The threedigit code of the station which paged you will be
displayed on your radio’s LCD.
Encryption
When the Voice Scrambler feature is enabled,
pressing the assigned Soft key of the “Encryption”
toggles the Scrambler “on” and “off.”
6
Cloning
The VX-410/-420 series includes a convenient Cloning feature, which allows the programming data from one transceiver to be transferred to another VX-410/-420 series. Here is the procedure for Cloning one radio's data to another.
1. Turn both transceivers off.
2. Remove the plastic cap and its two mounting screws
from the MIC/SP jack on the right side of the transceiver. Do this for both transceivers.
3. Connect the optional CT-27 cloning cable between the
MIC/SP jacks of the two transceivers.
4. Press and hold in the PTT and Soft key assigned to
“MONITOR” while turning the transceiver on. Do this
for both transceivers (the order of the switch-on does
not matter). “CLONE” will appear on the displays (for
the VX-420 series) of both transceivers when Clone
mode is successfully activated in this step; in the case
of the VX-410 series, no change will be observed at
this point.
5. On the Destination transceiver, press the Soft key assigned to “MONITOR”. “LOADING” will appear on the
LCD (for VX-420 series; for VX-410 series, the TX/
BUSY indicator on the top of the radio will glow
Green).
6. Press the PTT switch on the source transceiver; “SEND-
ING” will appear on the Source transceiver (for VX420 series; for VX-410 series, the TX/BUSY indica-
tor on the top of the radio will glow Red), and the data
will be transferred.
7. If there is a problem during the cloning process, “ER-
ROR” will appear on the LCD (for VX-420 series; for
VX-410 series, the TX/BUSY indicator on the top of
the radio will blink Red); check your cable connections and battery voltage, and try again.
8. If the data transfer is successful, the display will return
to “CLONE” (for VX-420 series; for VX-410 series,
the TX/BUSY indicator on the top of the radio will
turn off). Turn both transceivers off and disconnect the
CT-27 cable. You can then turn the transceivers back
on, and begin normal operation.
9. Replace the plastic cap and its two mounting screws.
Optional Cloning Cable CT-27
7
Specifications
GENERAL Specifications
Frequency Range: 450 - 490 MHz (D)
Number of Channels: 32 channels
Channel Spacing: 12.5 / 25 kHz
PLL Steps 5 / 6.25 kHz
Power Supply voltage: 7.5 VDC ± 10%
Operating Temperature Range: –22°F to +140°F (–30°C to +60°C)
Frequency Stability: ±2.5 ppm
Dimensions (WHD): 2.3" (W) x 4.3" (H) x 1.2" (D) (58 x 108 x 29 mm)
Weight (approx.): 0.78 lb. (350 g) w/FNB-V57, Antenna and Belt clip
RECEIVER Specifications (Measurements made per EIA standard TIA/EIA-603)
Sensitivity
EIA 12 dB SINAD : 0.25 µV
Adjacent channel selectivity: 70 dB (25 kHz) / 60 dB (12.5 kHz)
Intermodulation: 70 dB (25 kHz) / 65 dB (12.5 kHz)
Spurious and Image Rejection: 70 dB
Hum & Noise 45 dB
Audio output: 500 mW @4 Ohms, 10% THD
TRANSMITTER Specifications (Measurements made per EIA standard TIA/EIA-603)
Power output: 5.0 / 1.0 W
Modulation: 16K0F3E, 11K0F3E
Conducted Spurious Emissions: 70 dB Below Carrier
FM Hum & Noise: 45 dB (25 kHz) / 40 dB (12.5 kHz)
Audio distortion (@ 1 kHz): < 5 %
Measurements per EIA standards unless noted above. Specifications subject to change without notice or obligation.
8
RA0585700
WINDOW ASSY (VX-420U)
(W/ DOUBLE FACE TAPE)
RA0173500
CAP
R6147510
RING NUT (x 2 pcs)
RA0546100
KNOB ASSY (CH)
RA0546400
VOLUME KNOB
RA0210600
RUBBER PACKING
RA0545600
CR SPONGE RUBBER (VX-420U)
RA0546600
LCD HOLDER (VX-420U)
G6090156
LCD (VX-420U)
RA0546700
LIGHT GUIDE (VX-420U)
RA0546900
REFLECTOR SHEET (VX-420U)
(x 2 pcs)
Exploded View & Miscellaneous Parts
RA0545100 (Lot. 1~)
RA054510B (Lot. 2~)
FRONT CASE ASSY
(W/ LIGHT GUIDE,NAME PLATE,SP NET,SPEAKER,PACKING PAD,
PTT KNOB,SHEET(MIC),CR SPONGE RUBBER,WINDOW ASSY)
RA0545700 (Lot. 1~)
RA054570B (Lot. 2~)
FRONT CASE ASSY
(W/ LIGHT GUIDE,NAME PLATE,SP NET,SPEAKER,
PACKING PAD,PTT KNOB,SHEET(MIC))
RA0545400
PTT KNOB
RA0546500
RUBBER KNOB
(VX-420U)
RA0546800
INTER CONNECTOR
(VX-420U)
MAIN Unit
M3290039
MIC (W/ HOLDER RUBBER)
RA0584800
SHEET
CAUTION
correct incorrect
RA010700A
TERMINAL PLATE (+)
RA010340B
TERMINAL HOLDER
RA0351600
TERMINAL PLATE (-)
RA0337900
GROUND PLATE
BATTERY PACK
CP7806001
BELT CLIP ASSY
NAME PLATE
RA0546000
RUBBER PACKING
RA0123500
LATCH NAIL B
RA0545900
REAR CASE ASSY
(w/SMA CONNECTOR,
TERMINAL PLATE (-),
PAN HEAD SCREW M2X3NI)
RA0376900
SHEET
DUMMY Unit
RA0376900
SHEET
REF. VXSTD P/N Description Qty.
U44104002 TAPTITE SCREW M2X4NI 7
U44104002
(VX-420U)
TAPTITE SCREW M2X4NI 2
U20206007 BINDING HEAD SCREW M2.6X6B 2
U24110002 TAPTITE SCREW M2X10NI 2
U02206007 SEMS SCREW SM2.6X6B 2
U00103002 PAN HEAD SCREW M2X3NI 1
U9900158 TAPTITE SCREW 2X4NI 1
SUPPLIED ACCESSORIES
VXSTD P/N Description Qty.
Q3000142 RUBBER DUCK ANTENNA ATU-6D 1
Non-designated parts are available only as part of a designated
assembly.
9
Note:
10
Block Diagram
11
Note:
12
Circuit Description
Receive Signal Path
Incoming RF from the antenna jack is delivered to the
RF Unit and passes through a low-pass filter consisting of
coils L1001, L1002, and L1003, capacitors C1001, C1002,
C1021, C1022, C1023, C1024, C1025, C1026, and C1027,
and antenna switching diode D1004 (RLS135).
Signals within the frequency range of the transceiver
enter a varactor-tuned band-pass filter consisting of coils
L1012 and L1015, capacitors C1058, C1059, C1085,
C1118, and C1119, and diodes D1007, D1008, D1009,
and D1010 (all HVD350B), then are amplified by Q1019
(2SC5006) and enter a varactor-tuned band-pass filter
consisting of coils L1019, L1020, and L1025, capacitors
C1122, C1150, C1151, C1152, C1153, C1154, C1155,
C1156, C1177, C1178, C1179, C1180, and C1181, and
diodes D1012, D1013, and D1016 (all HVD350B), before application to the first mixer, Q1029 (3SK320).
Buffered output from the VCO is amplified by Q1026
(2SC5005) to provide a pure first local signal between
399.15 and 439.15 MHz for injection to the first mixer
Q1029. The 50.85 MHz first mixer product then passes
through monolithic crystal filter XF1001 (MFT50.85PT,
5.5 kHz BW) to strip away unwanted mixer products, and
is then amplified by Q1041 (2SC4215Y).
The amplified first IF signal is applied to FM IF sub-
system IC Q1048 (TA31136FN), which contains the sec-
ond mixer, second local oscillator, limited amplifier, noise
amplifier, and RSSI amplifier.
The second local signal is produced from the PLL ref-
erence/second local oscillator of X1002 (TCXO
TTS05VS-M1 16.80 MHz). The 16.80 MHz reference
signal is tripled by Q1048, capacitor C1251, and coil
L1042, and the resulting the 50.4 MHz second local signal is then delivered to the mixer section of Q1048 which
produces the 450 kHz second IF when mixed with the
first IF signal.
The second IF then passes through the ceramic filter
CF1001 (ELFC450G on “Narrow” channels) or CF1002
(ELFY450E on “Wide” and “Narrow” channels) to strip
away all but the desired signal, and is then applied to the
limiter amplifier in Q1048, which removes amplitude
variations in the 450 kHz IF, before detection of the speech
by the ceramic discriminator CD1001 (ECDA450C24).
Squelch Control
The squelch circuitry consists of a noise amplifier,
band-pass filter, and noise detector within Q1048
(TA31136FN).
When no carrier is received, noise at the output of the
detector stage in Q1048 is amplified and band-pass filtered by the noise amplifier section of Q1048 and the network between pins 7 and 8, and then is rectified by detection circuit in Q1048.
The resulting DC squelch control voltage is passed to
pin 19 of the microprocessor Q1047 (LC87F74C8A). If
no carrier is received, this signal causes pin 19 of Q1047
to go high and pin 30 to go high. Pin 35 signals Q1006
(2SC4154E) to disable the supply voltage to the audio
amplifier Q1005, while pin 30 holds the green (Busy) half
of the LED off, when pin 35 is high and pin 30 is high.
Thus, the microprocessor blocks output from the audio amplifier, and silences the receiver, while no signal is
being received (and during transmission, as well).
When a carrier appears at the discriminator, noise is
removed from the output, causing pin 19 of Q1047 to go
low and the microprocessor to activate the “Busy” LED
via Q1047.
The microprocessor then checks for CTCSS or CDCSS
code squelch information, if enabled. If not transmitting
and CTCSS or CDCSS is not activated, or if the received
tone or code matches that programmed, audio is allowed
to pass through the audio amplifier Q1005 (NJM2070M)
to the loudspeaker by the enabling of the supply voltage
to it via Q1048.
Transmit Signal Path
Speech input from the microphone MC1001 passes
through the audio amplifier Q1021 (AK2342B) to Q1015
(M62364FP) which adjusts the microphone gain. The adjusted audio is applied to the compander Q1010
(LA8630M) which compresses the speech signal according to a control command from the microprocessor Q1047
(LC87F74C8A).
The compressed speech signal passes through the
dummy unit and pre-emphasis circuit to Q1021, which
contains the low-pass filter, Voice Scrambler selector, and
high-pass filter.
The output from Q1021 is applied to the AF mute gate
Q1055 (2SK3541), then returns to Q1021, which contains the limiter amplifier, splatter filter and audio amplifier.
The filtered audio signal is applied to Q1015
(M62364FP) which is adjusts the audio level, then is applied to varactor diode D1017 (HVD350B), which frequency modulates the VCO Q1033 (2SK508). A portion
of the audio signal from Q1015 is applied to TCXO X1002
(TTS05VS).
The processed audio may then be mixed with a CTCSS
tone generated by Q1047 (LC87F74C8A) for frequency
modulation of the PLL carrier (up to ±5 kHz from the
unmodulated carrier) at the transmitting frequency.
If a CDCSS code is enabled for transmission, the code
is generated by microprocessor Q1047 and delivered to
X1002 (TCXO TTS05VS) for CDCSS modulating.
The modulated signal from the VCO Q1033 (2SK508-
K52) is buffered by Q1026 (2SC5005). The low-level
transmit signal then passes through the T/R switching di-
13
Loading...