DUAL BAND TRANSCEIVER
S-15120XZ-C1
March 2015
INTRODUCTION CAUTION
This service manual describes the latest technical informa-
tion for the IC-2730A and IC-2730E
DUAL BAND TRANSCEIVER, at
the time of publication.
MODEL VERSION
TPE-01 #04 25 W/15 W/5 W
IC-2730A
IC-2730E
USA-01 #05
KOR-01 #06
EXP-01 #09
EUR-01 #02
ITR-01 #03
CHN-01 #10
VERSION
NUMBER
TX POWER
50 W/15 W/5 W
NEVER connect the transceiver to an AC outlet or to a DC
power supply that uses more than the specifi ed voltage. This
will ruin the transceiver.
DO NOT expose the transceiver to rain, snow or liquids.
DO NOT reverse the polarities of the power supply when con-
necting the transceiver.
DO NOT apply an RF signal of more than 20 dBm (100 mW)
to the antenna connector. This could damage the transceiv-
er’s front-end.
To upgrade quality, any electrical or mechanical parts
and internal circuits are subject to change without notice
or obligation.
(IC-2730A)
ORDERING PARTS
Be sure to include the following four points when ordering
replacement parts:
1. 10-digit Icom part number
2. Component name
3. Equipment model name and unit name
4. Quantity required
1. Make sure that the problem is internal before dis-assem-
bling the transceiver.
2. DO NOT open the transceiver until the transceiver is dis-
connected from its power source.
3. DO NOT force any of the variable components. Turn them
slowly and smoothly.
4. DO NOT short any circuits or electronic parts. An insulated
REPAIR NOTES
tuning tool MUST be used for all adjustments.
<ORDER EXAMPLE>
1110003491 S.IC TA31136FNG IC-2730A MAIN UNIT 5 pieces
8820001210 Screw 2438 screw IC-2730E Top cover 10 pieces
5. DO NOT keep power ON for a long time when the trans-
ceiver is defective.
6. DO NOT transmit power into a Standard Signal Generator
or a Sweep Generator, otherwise the RF power may dam-
Addresses are provided on the inside back cover for your
convenience.
age them.
7. ALWAYS connect a 50 dB to 60 dB attenuator between the
transceiver and a Deviation Meter or Spectrum Analyzer,
when using such test equipment.
8. READ the instructions of the test equipment thoroughly
before connecting it to the transceiver.
Icom, Icom Inc. and the Icom logo are registered trademarks of Icom Incorporated (Japan) in Japan, the United States, the
United Kingdom, Germany, France, Spain, Russia, Australia, New Zealand, and/or other countries.
TABLE OF CONTENTS
SECTION 1 SPECIFICATIONS
SECTION 2 INSIDE VIEWS
SECTION 3 DISASSEMBLY INSTRUCTION
SECTION 4 CIRCUIT DESCRIPITON
4-1 RECEIVER CIRCUITS ...................................................................................... 4-1
4-2 TRANSMIT CIRCUITS ...................................................................................... 4-5
4-3 FREQUENCY SYNTHESIZER CIRCUITS ....................................................... 4-7
4-4 VOLTAGE BLOCK DIAGRAM ........................................................................... 4-8
SECTION 5 ADJUSTMENT PROCEDURES
5-1 PREPARATION ................................................................................................. 5-1
5-2 FREQUENCY ADJUSTMENT .......................................................................... 5-3
5-3 TRANSMIT ADJUSTMENT ............................................................................... 5-3
5-4 RECEIVE ADJUSTMENT ................................................................................. 5-5
SECTION 6 PARTS LIST
SECTION 7 MECHANICAL PARTS
SECTION 8 BOARD LAYOUTS
SECTION 9 BLOCK DIAGRAM
SECTION 10 VOLTAGE DIAGRAM
SECTION 1. SPECIFICATIONS
DGeneral
• Frequency coverage:
EUR
ITR
TPE RX, TX 144–146 MHz, 430–432 MHz
USA
KOR RX, TX 144–146 MHz, 430–440 MHz
EXP,
CHN
*1 Guaranteed only 144–146 MHz *2 Guaranteed only 430–440 MHz *3 Not guaranteed *4 Guaranteed only 144–148 MHz *5 Guaranteed only 430–450 MHz
RX 118–174 MHz*
TX 144–146 MHz, 430–440 MHz
RX 118–136.99166 MHz*
TX 144–146 MHz, 430–434 MHz, 435–438 MHz
RX 118–174 MHz*
TX 144–148 MHz, 430–450 MHz*
RX 118–174 MHz*
TX 137–174 MHz*4, 400–470 MHz*
• Mode: F2D/F3E (FM/FM-N),
• Number of memory channels: 1000 channels
• Number of program scan channels: 25 channels
• Number of call channels: 2 channels
• Scan types: Full, Band, Program, Priority, Memory channel, Bank, Skip and Tone scans
• Antenna connector: SO-239
• Antenna impedance: 50 ø
• Usable temperature range: –10˚C to +60˚C, +14˚F to +140˚F
• Frequency stability: ±2.5 ppm (−10˚C to +60˚C, +14˚F to +140˚F)
• Frequency resolution: 5 kHz, 6.25 kHz, 8.33 kHz, 10 kHz, 12.5 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 50 kHz
The 8.33 kHz step is not selectable, depending on the operating band or mode.
• Power supply: 13.8 V DC ±15% (negative ground)
• Current drain:
Transmit
Maximum current drain: 10.5 A at 25 W (TPE version)
Receive
Standby: 1.2 A
Maximum audio: 1.8 A
• Dimensions (projections not included):
Main unit: 150(W) 40(H) 151(D) mm, 5.9(W) 1.6(H) 5.9(D) inches
Controller:
• Weight (approximately):
Main unit: 1.2 kg, 2.6 lb
Controller: 140 g, 4.9 oz
1
, 375–550 MHz*
3
, 144–146 MHz, 430–434 MHz, 435–438 MHz
4
, 375–550 MHz*
4
, 375–550 MHz*
2
5
5
2
2
A3E (AM/AM-N) RX only
(2 edge frequencies in each channel)
150(W) 50(H) 27.2(D) mm,
13.0 A at 50 W (Other versions)
5.9(W) 2(H) 1.1(D) inches
D
Transmitter
• Modulation system: Variable reactance frequency modulation
• Type of emission: F2D, F3E
• Maximum deviation:
FM: ±5.0 kHz
FM-N: ±2.5 kHz
• Input impedance (Mic): 600 ø
• Spurious emission: –60 dBc
• Output power: High 25 W, Mid 15 W, Low 5 W (TPE version)
High 50 W, Mid 15 W, Low 5 W (Other versions)
1-1
D
Receiver
• Receive system: Double superheterodyne system
• IF frequencies:
Left band 1st IF 38.85 MHz
2nd IF 450 kHz
Right band 1st IF 46.35 MHz
2nd IF 450 kHz
• Sensitivity (except spurious points):
Amateur bands
FM/FM-N (12 dB SINAD)
0.18 µV
Except Amateur bands
FM/FM-N (12 dB SINAD)
0.32 µV (137.000–159.995 MHz)
0.56 µV (160.000–174.000 MHz)
0.56 µV (375.000–399.995 MHz)
0.32 µV (400.000–499.995 MHz)
0.56 µV (500.000–550.000 MHz)
AM (10 dB S/N)
1 µV (118.000–136.99166 MHz)
• Squelch sensitivity: 0.13 µV (Threshold)
• Selectivity:
FM 60 dB
FM-N 55 dB
• Spurious and image rejection ratio:
60 dB
55 dB (Left band UHF)
• AF output power: 2.0 W (at 10% distortion into an 8 ø load)
• Output impedance (Speaker): 8 ø
1-2
SECTION 2. INSIDE VIEWS
• CONTROL UNIT
+3.3 V REGULATOR
(IC6)
CPU
(IC1)
LCD DRIVER
(IC2)
RESET IC
(IC5)
+3.3 V REGULATOR
(IC7)
CLONING DATA LINE BUFFER
(IC102)
2-1
CLONING DATA LINE BUFFER
(IC312)
AND LOGIC GATE IC
(IC108)
AF SW
(IC109)
ELECTRONIC VOLUME IC
(IC110)
+3.3 V REGULATOR
(IC314)
+5 V REGULATOR
(IC319)
AF LINE MUTE SW
(IC111)
D/A CONVERTER
(IC1)
1ST IF FILTER (Right band)
(FI105)
• MAIN UNIT
(TOP VIEW)
RESET IC
(IC308)
EEPROM
(IC301)
NOISE AMP (Left band)
(IC123)
NOISE AMP (Right band)
(IC122)
MIC MUTE SW/MIC GAIN SW
(IC100)
VOX AMP/IDC AMP/AF LPF
(IC112)
AF LPF/AF BUFFER
(IC103)
D/A CONVERTER
(IC102)
MODULATION MUTE SW
(IC205)
IF IC (Left band)
(IC121)
EXPANDER
(IC316)
EXPANDER
(IC315)
EXPANDER
(IC317)
MIC AMP
(IC101)
IF IC (Right band)
(IC120)
1ST IF FILTER (Right band)
(FI104)
2-2
• MAIN UNIT
(BOTTOM VIEW)
DISCRIMINATOR (Right band)
(X101)
2ND IF FILTER (Right band)
(FI101)
2ND IF FILTER (Right band)
(FI100)
TX POWER AMP (UHF band)
(IC4)
TX POWER AMP
(VHF band)
(IC3)
+3.3 V REGULATOR
(IC311)
CURRENT DETECTOR IC
(IC310)
+8 V REGULATOR
(IC321)
+8 V REGULATOR
(IC325)
+8 V REGULATOR
(IC313)
PLL IC (Right band)
(IC206)
REFERENCE FREQUENCY
OSCILLATOR (Right band)
(X201)
DISCRIMINATOR (Left band)
(X102)
2ND IF FILTER (Left band)
(FI103)
2ND IF FILTER (Left band)
(FI102)
PLL IC (Left band)
(IC201)
REFERENCE FREQUENCY
OSCILLATOR (Left band)
(X200)
AF LINE SW
(IC119)
AF MUTE SW
(IC104)
CPU
(IC300)
+3.3 V REGULATOR
(IC306)
AF POWER AMP
(IC105)
AF POWER AMP
(IC106)
VOLTAGE DETECTOR IC
(IC324)
VOLTAGE DETECTOR IC
(IC320)
CLOCK OSCILLATOR
(X300)
2-3
SECTION 3. DISASSEMBLY INSTRUCTION
1. Removing the CONTROL UNIT
1) Remove all knobs from the controller.
Controller
2) Remove four screws from the rear panel.
3) Separate the rear panel from the front panel as-
sembly.
Front panel assembly
Rear panel
4) Remove the CONTROL UNIT from the front panel.
Front panel
2. Removing the MAIN UNIT
1) Remove eight screws from the top cover.
2) Remove the top cover from the chassis.
Top cover
Screws ×8
CHASSIS
3) Disconnect the speaker cable from the MAIN UNIT.
4) Remove the clip from the chassis.
Speaker
SPEAKER
CABLE
CONTROL UNIT
Clip
CHASSIS
5) Remove seven screws from the bottom cover.
Bottom cover
Screws×7
3-1
CHASSIS
(Continued on the next page.)
6) Unsolder three points at the antenna connector.
7) Disconnect the cooling fan cable.
UNSOLDER
Solder
remover
COOLING FAN
CABLE
8) Remove total of 17 screws from the MAIN UNIT.
Screws ×17
9) Remove the MAIN UNIT from the chassis.
MAIN UNIT
CHASSIS
3-2
SECTION 4. CIRCUIT DESCRIPTION
4-1 RECEIVE CIRCUITS
RF CIRCUITS
The received signal from the antenna connector passed
through the LPF (L90, L94, L96, C409, C418 and C428). The
fi ltered signal is applied to either the VHF or UHF band’s RF
circuit.
VHF BAND (118–174 MHz)
The received VHF band signal from the LPF (L90, L94, L96,
C409, C418 and C428) is passed through the LPF (L79, L83,
L87, C378, C386 and C394) and TX/RX SW (D66, D69 to
D71 and D77), and applied to the PRE-AMP (Q24).
• Left band
The amplifi ed signal is passed through the attenuator (D34)
and tuned BPF (D28, D88, L31, L34, C119, C127, C128 and
C135), and applied to the RF AMP (Q20). The amplifi ed sig-
nal is passed through the tuned BPF (D20, D87, L10, L18,
C60, C71, C74, C79 and C86), and then applied to the 1st
mixer (Q145).
• Right band
The amplifi ed signal is passed through the attenuator (D33)
and tuned BPF (D27, D85, L23, L32, L33, C116, C125, C126
and C132), and applied to RF AMP (Q19). The amplifi ed sig-
nal is passed through the tuned BPF (D19, D86, L9, L17,
C57, C69, C70, C77 and C84), and then applied to the 1st
mixer (Q143).
RF CIRCUITS
UHF TX circuit
VHF TX circuit
Left band
(VHF)
Right band
(VHF)
Left band
(UHF)
Right band
(UHF)
BPF
BPF
BPF
BPF
400-470MHz
137-174MHz
RF
AMP
RF
AMP
RF
AMP
RF
AMP
BPF
BPF
BPF
BPF
D68,D73,
D84,D75
TX/RX
SW
D66,D69
D70,D71,D77
TX/RX
SW
D34D28,D88Q20D20,D87
ATT
D33D27,D85Q19D19,D86
ATT
ANTENNA
HPF
AMP
Q24
RF
LIMITER
Q23
RF
AMP
118-550MHz
LPF
D79D81
LIMITER
375-550MHz
118-174MHz
LPF
118-174MHz
D32D22,D24,D26,D30Q18D12,D16,D91,D92
375-550MHz
ATT
D31D21,D23,D25,D29Q17D11,D15,D89,D90
ATT
UHF BAND (375–550 MHz)
The received UHF band signal from the LPF (L90, L94, L96,
C409, C418 and C428) is passed through the HPF (L84, L88,
C392, C395 and C429), TX/RX SW (D68, D73, D75, D84,
L86, L92, C387, C396 and C413), and applied to the PRE-
AMP (Q23).
• Left band
The amplifi ed signal is passed through the attenuator (D32)
and tuned BPF (D22, D24, D26, D30, L21, L28 and L101),
and applied to the RF AMP (Q18). The amplifi ed signal is
passed through the tuned BPF (D12, D16, D91, D92, L4,
L12, L16, L102, C33, C65 and C67), and then applied to the
1st mixer (Q146).
• Right band
The amplifi ed signal is passed through the attenuator (D31)
and tuned BPF (D21, D23, D25, D29, L22, L27 and L99), and
applied to the RF AMP (Q17). The amplifi ed signal is passed
through the tuned BPF (D11, D15, D89, D90, L3, L11, L15,
L100, C32, C63 and C66), and then applied to the 1st mixer
(Q144).
4-1
1ST IF CIRCUITS
VHF BAND
• Left band
The received signal from the RF circuit and 1st LO signal are
applied to the 1st IF mixer (Q145) and mixed, resulting in the
38.85 MHz 1st IF signal.
The 1st IF signal is applied to the 1st IF fi lter (FI105), through
the band SW (D121).
2ND IF CIRCUITS
• Left band
IC121 is an IF IC, which contains the 2nd mixer, limiter AMP,
noise AMP, quadrature detector, AM detector, AGC controller,
signal strength detector, and so on.
The 1st IF signal from the 1st IF AMP (Q138) and 38.4 MHz
2nd LO signal are mixed, resulting in the 450 kHz 2nd IF sig-
nal.
• Right band
The received signal from the RF circuit and 1st LO signal are
applied to the 1st IF mixer (Q143) and mixed, resulting in the
46.35 MHz 1st IF signal.
The 1st IF signal is applied to the 1st IF fi lter (FI104), through
the band SW (D119).
UHF BAND
• Left band
The received signal from the RF circuit and 1st LO signal are
applied to the 1st IF mixer (Q146) and mixed, resulting in the
38.85 MHz 1st IF signal.
The 1st IF fi lter is applied to the 1st IF fi lter (FI105), through
the band SW (D122).
• Right band
The received signal from the RF circuit and 1st LO signal are
applied to the 1st IF mixer (Q144) and mixed, resulting in the
46.35 MHz 1st IF signal.
The 1st IF signal is applied to the 1st IF fi lter (FI104), through
the band SW (D120).
The 2nd IF signal is output from pin 3, and passed through
the ceramic fi lter (FI102: For FM-N or FI103: For FM), and
then applied to IC121 from pins 5 and 7.
• Right band
IC120 is an IF IC, which contains the 2nd mixer, limiter AMP,
noise AMP, quadrature detector, AM detector, AGC controller,
signal strength detector, and so on.
The 1st IF signal from the 1st IF AMP (Q137) and 45.9 MHz
2nd LO signal are mixed, resulting in the 450 kHz 2nd IF sig-
nal.
The 2nd IF signal is output from pin 3, and passed through
the ceramic fi lter (FI100: For FM-N or FI101: For FM), and
then applied to IC120 from pins 5 and 7.
FM DEMODULATION CIRCUITS
• Left band
The 2nd IF signal applied pin 7 is amplifi ed by the limiter AMP,
and then demodulated by the quadrature detector with the
ceramic resonator (X102).
The demodulated AF signal is output from pin 11, and then ap-
plied to the AF circuit, through the AF SW (IC119, pins 8, 9).
The fi ltered signal is amplifi ed by the IF AMP (Q137), and ap-
plied to the IF IC (IC120, pin 20).
1ST IF CIRCUITS
Left band 1st LO (VHF)
Left band VHF RF circuit
Q145
Right band 1st LO (UHF)
Right band VHF RF circuit
Q143
Left band 1st LO (UHF)
Left band UHF RF circuit
Q146
Right band 1st LO (UHF)
Right band UHF RF circuit
Q144
Left band
2nd IF circuit
Right band
2nd IF circuit
FI105
Q138
IF
XTAL
AMP
BPF
38.85MHz
Left band 1st IF circuit
Q137
FI104
IF
XTAL
AMP
BPF
46.35MHz
Right band 1st IF circuit
D121,D122
RX
SW
D119,D120
RX
SW
• Right band
The 2nd IF signal applied pin 7 is amplifi ed by the limiter AMP,
and then demodulated by the quadrature detector with the
ceramic resonator (X101).
The demodulated AF signal is output from pin 11, and then ap-
plied to the AF circuit, through the AF SW (IC119, pins 1, 2).
4-2
AM DETECTOR CIRCUITS
• Left band
The 2nd IF signal applied from pin 5 is amplifi ed by the IF
AMP, and then demodulated by the amplitude detector in the
IF IC (IC121).
The demodulated AF signal is output from pin 14, and
then applied to the AF circuits, through the AF SW (IC119,
pins 11, 10).
2ND IF AND DEMODULATOR CIRCUITS (Left band)
X200
Q200
38.4MHz
X3
Left band
AF circuit
IC119
DET OUT
SELECT
AM
FM
D107,D108,D111,D112
12.8MHz
IF IC
WIDE/NARROW
X102
IC121
Left band
1st IF circuit
In the AM mode, the AGC circuit in the IF IC automatically
adjusts the gain of RF AMPs (Q18 and Q20) and 1st IF AMP
(Q138), to keep the signal level constant.
The demodulated AF signal is applied to the RX AF circuit.
• Right band
The 2nd IF signal applied from pin 5 is amplifi ed by the IF
AMP, and then demodulated by the amplitude detector in the
IF IC (IC120).
The demodulated AF signal is output from pin 14, and then
applied to the AF circuits, through the AF SW (IC119, pins
4, 3).
In the AM mode, the AGC circuit in the IF IC automatically
adjusts the gain of RF AMPs (Q17 and Q19) and 1st IF AMP
(Q137), to keep the signal level constant.
The demodulated AF signal is applied to the RX AF circuit.
CERAMIC
CERAMIC
BPF
FI102 FI103
BPF
LIF
2ND IF AND DEMODULATOR CIRCUITS (Right band)
X201
Q220
45.9MHz
X3
Right band
AF circuit
DET OUT
SELECT
AM
FM
CERAMIC
FI100 FI101
IF IC
WIDE/NARROW
D105,D106,D109,D110
CERAMIC
BPF
BPF
15.3MHz
X101
IC120IC119
Right band
1st IF circuit
RIF
4-3
RX AF CIRCUITS
• Left band
The demodulated AF signal from the AF SW (IC119) is
passed through the AF mute SW (IC111, pins 4, 3) and AF fi l-
ter (Q113), and then applied to the volume IC (IC110, pin 4),
which adjusts the AF signal in level.
The level-adjusted AF signal from the volume IC (IC110,
pin 11) is passed through the AF SW (IC109, pins 2, 1), which
selects the AF signal from Left and Right bands.
When output from [EXTERNAL SPEAKER JACK1]
The output signal from the AF SW (IC109) is passed through
the AF MUTE SW (Q104 and Q105), and applied to the AF
AMP (IC105, pin 1).
The amplifi ed AF signal is applied to the internal speaker
(CHASSIS: SP1) or an external speaker, through [EXTER-
NAL SPEAKER JACK1] (J101).
• Right band
The demodulated AF signal from the AF SW (IC119) is
passed through the AF mute SW (IC111, pins 8, 9) and AF
fi lter (Q112), and then applied to the volume IC (IC110, pin 3),
which adjusts the AF signal in level.
The level-adjusted AF signal from the volume IC (IC110,
pin 12) is passed through the AF SW (IC109, pins 3, 4), which
selects the AF signal from Left and Right bands.
• RX AF CIRCUITS
J101
SP1
J102
IC105 Q104 Q105
AF
SP
AMP
MUTE
IC106
AF
AMP
Optional module
Q106
MUTE
BTAF
MUTE
SP
SP
IC109
AFSW
IC107
BUFF
When output from [EXTERNAL SPEAKER JACK2]
The output signal from the AF SW (IC109) is passed through
the AF MUTE SW (Q106), and applied to the AF AMP (IC106,
pin 1).
The amplifi ed AF signal is applied to [EXTERNAL SPEAKER
JACK2] (J102).
TX AF circuit
IC110 IC111
ELEC.
IC103
AF
FIL
Q113,Q140
AF
FIL
Modulation circuit
IC103
BUFF
IC103
BUFF
DETMUTE
L_RMUTE R_RMUTE
2nd IF circuit (Left band )
2nd IF circuit (Right band )
LPF
RPT
IC104
RPT
SW
Q112,Q139
VR
4-4
4-2 TRANSMIT CIRCUITS
TX AF CIRCUIT (CONTROL AND MAIN UNITS)
When the microphone is connected to the controller:
The AF signal from the microphone is applied to the MIC
AMP (CONTROL UNIT: IC102, pin 2), through [MIC] (CON-
TROL UNIT: J101). The amplifi ed MIC signal is applied to the
MIC line SW (MAIN UNIT: IC100, pin 1) on the MAIN UNIT,
through the control cable.
MODULATION CIRCUITS (MAIN UNIT)
The modulation signal from the TX AF circuit is applied to the
VCO as the frequency modulation signal.
VHF BAND
The modulation signal is applied to the VHF VCO (Q211,
D203, D204, D206, D228 and D342).
When the microphone is directly connected to the MAIN UNIT:
The AF signal from the microphone is applied to the MIC
AMP (MAIN UNIT: IC101, pin 5), through [MIC] (MAIN UNIT:
J100).
The amplifi ed MIC signal is passed through the MIC line
SW (MAIN UNIT: IC100, pins 11, 10), MIC gain SW (MAIN
UNIT: Q151 and Q152), MIC mute SW (MAIN UNIT: IC100,
pins 9, 8) and the HPF (MAIN UNIT: R774, C861 and C862),
and then adjusted in amplitude by the IDC AMP (MAIN UNIT:
IC112, pins 3, 1), and passed through the splatter fi lter (MAIN
UNIT: IC112, pins 13, 14) and LPF (MAIN UNIT: IC103,
pins 6, 7), and then applied to the D/A converter (MAIN UNIT:
IC102, pin 13).
The level-adjusted MIC signal is passed through the modula-
tion mute SW (MAIN UNIT: VHF band IC205, pins 2, 1/UHF
band IC205, pins 3, 4), and then applied to the modulation
circuit as the modulation signal.
TX AF CIRCUIT
From the
optional
IC307
unit
BTMIC
BUFF
J100
1
2
3
4
5
6
MIC
7
8
CONTROL UNIT
IC101
MIC
AMP
IC100
MIC
SW
Q151/Q152
MIC
MIC
GAIN
MUTE
SW
SW
J6
1
2
3
4
5
6
IC112IC100 IC112
HPF
IDC
Left band RX signal
Right band RX signal
Splatter
IC103 IC102
LPF
LPF
IC104
RPT
RPT
SW
MAIN UNIT
D/A
The modulated VCO output signal is amplifi ed by the buffer
(Q215), passed through the LO SW (D208), amplifi ed by the
LO AMP (Q240), and then applied to the TX AMP circuit as
the TX signal, through another LO SW (D50).
UHF BAND
The modulation signal is applied to the UHF VCO (Q232,
D223, D224, D227, D229 and D236).
The modulated VCO output signal is amplifi ed by the buffer
(Q235), and then applied to the TX AMP circuit as the TX
signal.
MODULATION CIRCUITS
Q232
D236
D223
VCOMOD
IC205
MOD
MUTE
D224
D227
D229
Q211
D342
D203
D204
D206
D228
LVCO
Q215
BUFF
L_VHF
Q235
BUFF
R_UHF
Q240
LO
AMP
UHF TX CIRCUIT
D50
TX/RX
SW
VHF TX CIRCUIT
IC102
MIC
AMP
MICU/D
EXTMIC
MICE
MICIN
J101
8V
1
2
3
PTT
4
5
MIC
GND
[MIC]
6
7
8
4-5
TX AMP CIRCUITS (MAIN UNIT)
VHF BAND
The TX signal from the VHF band modulation circuit is passed
through the LPF (L50, L51, C215, C220 and C225) and ATT
(R146, R147 and R151), and then sequentially amplifi ed by
the pre-drive AMP (Q36), drive AMP (Q40) and power AMP
(IC3).
APC CIRCUITS
VHF BAND
A portion of RF signal is rectifi ed by the power detector di-
odes (D59 and D63) at the LPF (L67, L68, C291, C297,
C301, C302, C326, C331 and C332), and the produced DC
voltage, which represents the TX power level, is used as the
TX power sensing voltage.
The amplifi ed TX signal is passed through the LPF (L67, L68,
C291, C297, C301, C302, C326, C331 and C332), TX output
power detector (D59 and D63), ANT SW (D66) and two LPFs:
(L79, L83, L87, C378, C386, C394 and L90, L94, L96, C409,
C418, C428), before being applied to the antenna.
UHF BAND
The TX signal from the UHF band modulation circuit is ampli-
fi ed by the LO AMP (Q37), passed through the HPF (L52 and
C232), ATT (R155, R156 and R162), and then sequentially
amplifi ed by the pre-drive AMP (Q38), drive AMP (Q41) and
power AMP (IC4).
The amplifi ed TX signal is passed through the LPF (L69, L73,
C310, C319, C322, C323, C350, C358 and C359), TX output
power detector (D62 and D67), ANT SW (D68 and D84) and
HPF (L84, L88, C391, C392, C395, C402, C429 and C430)
and LPF (L90, L94, L96, C409, C418 and C428), before be-
ing applied to the antenna.
The TX power sensing voltage is applied to the APC AMP
(IC2, pin 2), and the power setting voltage from the D/A con-
verter (IC102, pin 8) is also applied to the AMP from pin 3,
resulting in the output voltage which is inversely proportional
to the TX power sensing voltage.
When the TX power sensing voltage increases, the output
voltage, which controls the gain of the power AMP (IC3), de-
creases to control the TX power constant.
UHF BAND
A portion of RF signal is rectifi ed by the power detector di-
odes (D62 and D67) at the LPF (L69, L73, C310, C319,
C322, C323, C350, C358 and C359), and the produced DC
voltage, which represents the TX power level, is used as the
TX power sensing voltage.
The TX power sensing voltage is applied to the APC AMP
(IC2, pin 6), and the power setting voltage from the D/A con-
verter (IC102, pin 7) is also applied to the AMP from pin 5,
resulting in the output voltage which is inversely proportional
to the TX power sensing voltage.
When the TX power sensing voltage increases, the output
voltage, which controls the gain of the power AMP (IC4), de-
creases to control the TX power constant.
TX AMP CIRCUITS
Q37
UHF band
VHF band
LO
AMP
ANTENNA
PWR
DET
D68/D73/
D84/D75
TX/RX
SW
UHF RX CIRCUIT
D66/D69
D70/D71/D77
TX/RX
SW
VHF RX CIRCUIT
Q38
PRE
ATT
HPF
DRIVE
Q36
PRE
ATT
DRIVE
D55 Q41 IC4 D62/D67
LIMITER
D53 Q40 IC3 D59/D63
LIMITER
DRIVE
AMP
DRIVE
AMP
LPFHPF
PWR
ATT
AMP
PWR
ATTLPF
AMP
IC2
LPF
APC
CTRL
PCON(V/U)
PWR
DET
UHF BAND
375-550MHz
HPFLPF
VHF BAND
118-174MHz
LPF
118-550MHz
LPF
4-6
4-3
FREQUENCY SYNTHESIZER CIRCUITS
(MAIN UNIT)
VCOs
The IC-2730A/E has total of four VCOs: two VCOs for the left
band and another two for the right band.
• Left band
VHF VCO
The VHF VCO (Q211, D203, D204, D206, D228 and D342)
generates the VHF TX signal. The output of buffer (Q215) is
amplifi ed by the LO AMP (Q240), and then applied to the
VHF TX AMP circuit, through the LO SW (D50).
UHF VCO
The UHF VCO (Q210, D201, D202 and D205) generates the
1st LO signal (for receiving a UHF signal on the left band).
The output of buffer (Q214) is amplifi ed by the LO AMP
(Q240), and then applied to the 1st IF mixer (Q146), through
the LO SW (D213) and LPF (L315, C988 and C995).
• Right band
VHF VCO
The VHF VCO (Q233, D225, D226 and D230) generates the
1st LO signal (for receiving a VHF signal on the right band).
The output of buffer (Q236) is amplifi ed by the LO AMP
(Q238), and then applied to the 1st IF mixer (Q143), through
the LO SW (D235) and LPF (L338, L339, C1105 and
C1106).
UHF VCO
The UHF VCO (Q232, D223, D224, D227, D229 and D236)
generates the UHF TX signal. The output of buffer (Q235) is
applied to the UHF TX AMP circuit.
• Left band frequency synthesizer circuit
137-174MHz
156.85-212.85MHz
LPF
Q145
LPF
336.15-511.15MHz
Q146
X200
12.8MHz
Q200
IF IC
X3
38.4MHz
Left band VCOs
IC201
IC121
LOOP
FIL
PLL
IC
Q210
D201
D202
D205
RX VCO (UHF)
Q211
D342
D203
D204
D206
D228
TX VCO (VHF)
Q214
Q215
BUFF
BUFF
BUFF
Q213
Q240
D50/D212/D213
AMP
TX/RX
SW
PLL
The PLL circuit controls the VCO oscillating frequency by
comparing the reference signal and the fed back VCO sig-
nal. When the oscillation frequency drifts, its phase changes
from that of the reference frequency, causing a lock voltage
change to compensate for the drift in the VCO oscillating fre-
quency.
• Left band
A portion of VHF and UHF VCOs output signal is ampli-
fi ed by the buffer (Q213), and then fed back to the PLL IC
(IC201, pin 17).
The PLL IC (IC201) phase-compares the output of reference
frequency oscillator (TCXO: X200) and VCO, and the phase
difference is output as the charge pump current. The current
is passed though the loop fi lter (R715, R717, R719, R722,
C924, C926 to C928 and C930) to be converted into the lock
voltage, which controls the oscillating frequency of VCO.
• Right band
A portion of VHF and UHF VCOs output signal is ampli-
fi ed by the buffer (Q234), and then fed back to the PLL IC
(IC206, pin 17).
The PLL IC (IC206) phase-compares the output of reference
frequency oscillator (TCXO: X201) and VCO, and the phase
difference is output as the charge pump current. The current
is passed though the loop fi lter (R797, R799, R802, R805,
C1041, C1043 to C1045 and C1048) to be converted into the
lock voltage, which controls the oscillating frequency of VCO.
• Right band frequency synthesizer circuit
Q232
D223
D224
D227
Q235
D229
D236
TX VCO (UHF)
Q233
D225
D226
D230
RX VCO (VHF)
BUFF
Q236
BUFF
BUFF
Q234
Q238
D234/D235
AMP
328.65-
503.65 MHz
400-470MHz
SW
164.35-
220.35 MHz
LPFLPF
Q143
Q144
X201
15.3MHz
Q220
X3
IF IC
45.9MHz
Right band VCOs
IC120
IC206
LOOP
FIL
PLL
IC
4-7
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