Yaesu FT-8900R Manual

1
Quad Band FM Transceiver
FT-8900R
Technical Supplement
Introduction
This manual provides technical information necessary for servicing the FT-8900R 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 thr board 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.
Specifications .................................................... 2
Exploded View & Miscellaneous Parts ........ 3
Connection Diagram ........................................ 4
Circuit Description........................................... 5
Alignment ........................................................ 11
Contents
Board Unit (Schematics, Layouts & Parts)
Main Unit .....................................................................17
Panel Unit.....................................................................47
Panel-Sub Unit .............................................................53
VR-L Unit .....................................................................55
VR-R Unit .....................................................................56
©2002 VERTEX STANDARD CO., LTD. (EH008M90A)
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.
International Division
8350 N.W. 52nd Terrace, Suite 201, Miami, FL 33166, 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
14
6
5
2
3
LOW
SQL SQL
VOL
VOL
LOW
V/M
HM
SCN
V/M
HM
SCN
KEY2
PWR

2
Specifications
GENERAL
Frequency Range:RX: 28.000 - 29.700 MHz, 50.000 - 54.000 MHz,
108.000 - 180.000 MHz, 320.000 - 480.000 MHz,
700 - 985 MHz (Cellular Blocked)
TX: 28.000 - 29.700 MHz, 50.000 - 54.000 MHz,
144.000 - 146.000 MHz (or 144.000 - 148.000 MHz),
430.000 - 440.000 MHz (or 430.00 - 450.000 MHz)
Channel Steps:5/10/12.5/15/20/25/50 kHz
Modes of Emission:F3, F2, F1
Antenna Impedance:50-Ohms, unbalanced (Antenna Duplexer built-in)
Frequency Stability:±5 ppm @ 14° F ~ +140° F (–10 °C ~ +60 °C)
Operating Temperature Range:–4° F ~ +140° F (–20 °C ~ +60 °C)
Supply Voltage:13.8 VDC (±15%), negative ground
Current Consumption (Approx.): RX: 0.5 A (Squelched)
TX: 8.0 A (50/430 MHz), 8.5 A (29/144 MHz)
Case Size (W x H x D): 5.5” x 1.6” x 6.6” (140 x 41.5 x 168 mm) (w/o knobs & connectors)
Weight (Approx.): 2.2 lb (1 kg)
TRANSMITTER
Output Power:50/20/10/5 W (29/50/144 MHz),
35/20/10/5 W (430 MHz)
Modulation Type:Variable Reactance
Maximum Deviation:±5 kHz (50/144/430 MHz),
±2.5 kHz (29 MHz)
Spurious Radiation:Better than –60 dB (29 MHz: Better than –50 dB)
Modulation Distortion:Less than 3%
Microphone Impedance:2 kW
DATA Jack Impedance:10 kW
RECEIVER
Circuit Type: Double-conversion superheterodyne
Intermediate Frequencies: 45.05 MHz/450 kHz (Left band),
47.25 MHz/450 kHz (Right band)
Sensitivity (for 12dB SINAD): Better than 0.2 µV
Squelch Sensitivity: Better than 0.16 µV
Selectivity (–6dB/–60dB): 8 kHz/30 kHz (50/144/430 MHz),
6 kHz/30 kHz (29 MHz)
Maximum AF Output: 2 W @ 8 Wfor 5% THD
AF Output Impedance: 4-16 W
Specifications are subject to change without notice, and are guaranteed within the 29, 50, 144, and 430 MHz amateur bands only.
Frequency ranges will vary according to transceiver version; check with your dealer.

3
Exploded View & Miscellaneous Parts
RA0396700
LIGHT GUIDE
RA0396800
LCD HOLDER
RA0396900 (x2 pcs)
INTER CONNECTOR
RA0397100
REFLECTOR SHEET
RA0397000
DIFFUSER SHEET
M2090034A
FAN
M4090149
SPEAKER
RA0404400 (x2 pcs)
KNOB
RA0404300 (x2 pcs)
KNOB
RA0404200 (x2 pcs)
ENCODER KNOB
R6054387B (x2 pcs)
SPECIAL NUT
RA040470A
FRONT PANEL ASSY
RA0407200
SPACER
T9207010A
WIRE ASSY
RA040710A
LIGHT SHEET
T9206438A
WIRE ASSY
R0150630
HOLDER
RA02132A0
HIMERON TAPE
CS1770001
CASE (W/O NYLON NET)
T9206228
WIRE ASSY
RA040480A
SUB PANEL ASSY
(W/ COIL SPRING, RELEASE KNOB)
T9101509
CT CABLE
S5000206
FAN GUARD
P1090984
CONNECTOR
RA0446200 (x2 pcs)
LEAF SPRING
RA0396100
REAR PANEL
RA02668AA
CHASSIS
RA0441300
PAD
RA0438700
RUBBER
G6090147A
LCD
VR-L Unit
VR-R UNIT
PANEL Unit
PANEL-SUB UNIT
MAIN UNIT
RA0415200 (x2 pcs)
GROUND PLATE
R0137550
COIL SPRING
RA026900A
RELEASE KNOB
•
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•
•
•
No. VXSTD P/N DESCRIPTION QTY.
•U23116007 TAPTITE SCREW M2X16B 4
‚U31206007 OVAL HEAD SCREW M2.6X6B 14
ƒU44308002 TAPTITE SCREW M3X8NI 17
„U03310002 SEMS SCREW ASM3X10NI 4
…U20308002 BINDING HEAD SCREW M3X8NI 2
†U20318007 BINDING HEAD SCREW M3X18B 4
Non-designated parts are available only
as part of a designated assembly.

4
Connection Diagram

5
Circuit Description
Receiver Signal Path
“Left” Band 430 MHz Signal
The 430 MHz signal is passed through ahigh-pass filter
network and alow-pass filter network to the antenna
switch diodesD1001/D1002 (both RLS135), then passed
through another low-pass filter network to the “Left” band
RF amplifier Q1001 (3SK296ZQ).
The amplified 430 MHz signal is passed through the band
switch D1008 (HSC277) to the varactor-tuned band-pass
filter network consisting of D1009, D1010, D1011 (all
HVC358B) and associated circuitry, then applied to the
first mixer Q1004 (3SK296ZQ). Meanwhile, the UHF lo-
cal signal from the UHF-VCO/A Q1112 (2SC5006) is de-
livered to first mixerQ1004, yielding the 45.05 MHz “Left”
band first IF.
“Left” Band 144 MHz Signal
The 144 MHz signal is passed through alow-pass filter
network and ahigh-pass filter network to the antenna
switching relay RL1001 (G5A-237P), then passedthrough
another high-pass filter network and low-pass filter net-
work to the “Left” band RF amplifier Q1006 (3SK296ZQ).
The amplified 144 MHz signal is passed through avarac-
tor-tuned band-pass filter network consisting of D1019,
D1020, D1021 (all HVC365) and associated circuitry to the
first mixer Q1010 (3SK296ZQ). Meanwhile, the VHF lo-
cal signal from the VHF-VCO/A Q1115 (2SC5374) is de-
livered to first mixerQ1010, yielding the 45.05 MHz “Left”
band first IF.
“Left” Band 50 MHz Signal
The 50 MHz signal is passed through alow-pass filter
network and antenna switching relayRL1003(G5A-237P),
then passed through another low-pass filter network, an-
tenna switch relay RL1002 (G5A-237P),and band switch
diode D1144 (HSC277) to yet another low-pass filter net-
work, then applied to the “Left” band RF amplifier Q1006
(3SK296ZQ).
The amplified 50 MHz signal is passed through aband-
pass filter network and band switch diode D1027
(HSC277) to the first mixer Q1015 (3SK296ZQ). Mean-
while, the 50 MHz local signal from the RX50-29-VCO
Q1121 (2SC5374) is delivered to first mixer Q1015, yield-
ing the 45.05 MHz “Left” band first IF.
“Left” Band 28 MHz Signal
The 28 MHz signal is passed through alow-pass filter
network and antenna switching relayRL1003(G5A-237P),
then passed through another low-pass filter network, an-
tenna switching relay RL1002 (G5A-237P) and band
switch diode D1144 (HSC277) to yet another low-pass fil-
ter network, then delivered to the “Left” band RF ampli-
fier Q1012 (2SC5374).
The amplified 28 MHz signal is passed through aband-
pass filter network and band switch diode D1028
(HSC277) to the first mixer Q1015 (3SK296ZQ). Mean-
while, the 28 MHz local signal from the RX50-29-VCO
Q1121 is delivered to first mixer Q1012, yielding the 45.05
MHz “Left” band first IF.
“Left” Band IF and AF Signals
The 45.05 MHz “Left” band first local signal is delivered
to the monolithic crystal filter XF1002 which stripsaway
unwanted mixer products, then is passed through IF am-
plifier Q1019 (2SC4400) to the IF ICQ1024 (TA31136FN).
Meanwhile, a portion of the output of 11.15 MHz crystal
X1003 is multiplied fourfold by Q1027 (2SC4400) to pro-
vide the 44.6 MHz second local signal, then delivered to
the IF IC Q1024. Within the IF IC Q1024, the 44.6 MHz
second local signal is mixed with the 45.05 MHz “Left”
band first local signal to produce the 450 kHz “Left” band
second IF.
The 450 kHz “Left” band second IF is passed through the
filter switch D1033/D1034 (both DAN235E) to the ceram-
ic filter CF1002 (CFWM450E) which strips away all but
the desired signal, then it passes through the IF amplifier
within Q1024 to the ceramic discriminator CD1002
(CDBM450C24),which removes any amplitude variations
in the 450 kHz IF signal before detection of speech.
The demodulated “Left” band audio is passed through
the de-emphasis network, audio switch D1035 (DAN222),
low-pass filter network (consisting of Q1034 (NJM2902V)
and associated circuitry), and ahigh-pass filter network
(consisting of Q1025 (NJM2092V) and associated circuit-
ry). The filtered audio signal is passed through the audio
volume control ICQ1042 (M511312FP),which adjusts the
audio sensitivity to compensate for audio level variations,
then is delivered to the audio switch Q1046 and Q1047
(both TC4W66FU).
When the internal speaker is selected, the audio signal is
amplified by Q1050 (TDA7233D) then applied to the in-
ternal loudspeaker. When the external speaker is select-
ed, the audio signal is amplified by Q1045 (LA4425A),
then it passes through theEXT SP jack to the external loud-
speaker.
“Right” Band 430 MHz Signal
The 430 MHz signal is passed through ahigh-pass filter
network and alow-pass filter network to the antenna
switch diodesD1001/D1002, then passed through anoth-
er low-pass filter network to the “Right” band RF ampli-
fier Q1002 (3SK296ZQ).
The amplified 430 MHz signal is delivered through the
band switch D1008 (HSC277) to the varactor-tuned band-
pass filter network consisting of D1004, D1005, D1006 (all
HVC358B) and associated circuitry, then applied to the

6
first mixer Q1003 (3SK296ZQ). Meanwhile, the UHF lo-
cal signal from the UHF-VCO/B Q1106 (2SC5006) is de-
livered to first mixer Q1004, yielding the 47.25 MHz
“Right” band first IF.
“Right” Band 144 MHz Signal
The 144 MHz signal is passed through alow-pass filter
network and ahigh-pass filter network to the antenna
switching relay RL1001 (G5A-237P), then passedthrough
another high-pass filter network and low-pass filter net-
work to the “Right” band RF amplifier Q1007
(3SK296ZQ).
The amplified 144 MHz signal is passed through the var-
actor-tuned band-pass filter network consisting of D1016,
D1017, D1018 (all HVC365) and associated circuitry to the
first mixer Q1008 (3SK296ZQ). Meanwhile, the VHF lo-
cal signal from the VHF-VCO/B Q1109 (2SC5374) is de-
livered to first mixer Q1008, yielding the 47.25 MHz
“Right” band first IF.
“Right” Band IF and AF Signal
The 47.25 MHz “Right” band first IF is delivered to the
monolithic crystal filter XF1001 which stripsaway un-
wanted mixer products, then passed through the IF am-
plifier Q1017 (2SC4400) to the IF ICQ1018 (TA31136FN).
Meanwhile, a portion of the output of 11.7 MHz crystal
X1002 is multiplied fourfold by Q1026 (2SC4400) to pro-
vide the 46.8 MHz second local signal, then applied to the
IF IC Q1018. Within the IF IC Q1018, the 46.8 MHz sec-
ond local signal is mixed with the 47.25 MHz “Right” band
first local signal to produce the 450 kHz “Right” band sec-
ond IF.
The 450 kHz “Right” band second IF is delivered to the
ceramic filter CF1001 (CFWM450E) which strips away all
but the desired signal, then passed through the IF ampli-
fier within Q1018 to the ceramic discriminator CD1001
(CDBM450C24) which removes any amplitude variations
in the 450 kHz IF signal before detection of speech.
The demodulated “Right” band audio is passed through
the de-emphasis network, low-pass filter network (con-
sisting of Q1033 (NJM2902V) and associated circuitry) and
the high-pass filter network (consisting of Q1025
(NJM2092V) and associated circuitry). The filtered audio
signal is passed through the audio volume control IC Q1042
(M511312FP), which adjusts the audio sensitivity to com-
pensate for audio level variations, then is delivered to the
audio switch Q1046 and Q1047 (both TC4W66FU).
When the internal speaker is selected, the audio signal is
amplified by Q1050 (TDA7233D) then applied to the in-
ternal loudspeaker. When the external speaker is select-
ed, the audio signal is amplified by Q1045 (LA4425A),
then it passes through theEXT SP jack to the external loud-
speaker.
Squelch Control
“Left” Band
When no carrieris being received on the “Left” band, noise
at the output of the detector stage in Q1024 is amplified
and band-pass filtered by the noise amp section of Q1024.
The resulting DC voltage is delivered to pin 2 of main
CPU Q1084 (M38268MCL), which compares the squelch
threshold level to that which set by the front panel SQL
knob.
While no carrier is being received on the “Left” band, pins
43 and 45 of Q1084 remain “low,” to disable the audio
switch Q1046/Q1047, thus disabling the audio output from
the speaker.
“Right” Band
When no carrier is being received on the “Right” band,
noise at the output of the detector stage in Q1018 is am-
plified and band-pass filtered by the noise amp section of
Q1018. The resulting DC voltage is delivered to pin 5 of
main CPU Q1084, which compares the squelch threshold
level to that which set by the front panel SQL knob.
While no carrier is being received on the “Left” band, pins
42 and 44 of Q1084 remain “low,” to disable the audio
switch Q1046 and Q1047, thus disabling the audio out-
put from the speaker.
Transmitter Signal Path
AF Signal
The speech signal from the microphone is passed through
the MIC jackJ3003 to the AF amplifierQ3001 (NJM2904V)
on the PANEL-SUB UNT. The amplified speech signal is
passed through the panel separation jacks J3001 andJ1005
to the MAIN Unit. On the MAIN UNIT, the speech signal
is delivered to the limiting amplifier Q1054 (NJM2902V)
to prevent over-modulation, then is delivered to alow-
pass filter network consisting of Q1054 and associated cir-
cuitry.
430 MHz Signal
The adjusted speech signal from Q1054 is passed through
transistor switch Q1051 (BU4066BCFV) to varactor di-
odes D1069 (HVC375) and D1070 (HVC350B),which fre-
quency modulate the transmitting VCO,made up of UHF-
VCO/B Q1106 (2SC5006) and D1071 (HSC277).
The modulated transmit signal is passed through buffer
amplifiersQ1107, Q1108, and Q1146 (all 2SC5006) and
diode switches D1073 (HSC277) and D1128 (DAN235E)
to the pre-drive amplifier Q1139 (2SK2596).
The amplified transmit signal from Q1139 is passed
through diode switch D1134 (HSC277) and the driver
amplifier Q1137 (2SK2975) to the diode switch D1134
(HSC277), then finally amplified by power amplifier
Circuit Description

7
Q1134 (RD70HVF1), providing up to 35 Watts of power
output. These three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 35-Watt RF signal is passed through a high-pass filter
network to the antenna switch D1102, D1104,and D1146
(all UM9957F), then passed through a low-pass filter net-
work and another high-pass filter network to the ANT
jack.
144 MHz Signal
The adjusted speech signal from Q1054 is passed through
the transistor switch Q1051 (BU4066BCFV) to varactor
diodesD1076 and D1077 (both HVC365),which frequen-
cy modulate the transmitting VCO,made up of VHF-VCO/
BQ1109 (2SC5374) and D1078 (HSC277).
The modulated transmit signal is passed through buffer
amplifiersQ1100 and Q1111 (both 2SC5374) and diode
switches D1075 (HSC277) and D1128 (DAN235E) to the
pre-drive amplifier Q1139 (2SK2596).
The amplified transmit signal from Q1139 is passed
through the diode switch D1139/D1140 (both HSC277)
and the driver amplifier Q1137 (2SK2975) to diode switch
D1133 (RLS135), then finally amplified by power ampli-
fier Q1134 (RD70HVF1) up to 50 Watts of power output.
These three stages of the power amplifier’s gain are con-
trolled by the APC circuit.
The 50-Watt RF signal is passed through a low-pass filter
network to the antenna switching relay RL1001 (G5A-
237P), then passed through a high-pass filter network and
another low-pass filter network to the ANT jack.
50 MHz Signal
The adjusted speech signal from Q1054 is passed through
transistor switch Q1086 (BU4066BCFV) to varactor di-
ode D1093 (HVC300A),which frequency modulates the
transmitting VCO,made up of TX50-29-VCO Q1118
(2SC5374) and D1094 (HSC277).
The modulated transmit signal is passed through buffer
amplifier Q1119 (2SC5374) to the pre-Drive amplifier
Q1123 (2SC5374).
The amplified transmit signal from Q1123 is passed
through diode switches D1127 (DAN235E) and D1141
(HSC277) and driveramplifier Q1137 (2SK2975) to di-
ode switch D1132 (D1F20), then finally amplified by pow-
er amplifier Q1134 (RD70HVF1) up to 50 Watts of power
output. These three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 50-Watt RF signal is passed through antenna switch-
ing relay RL1002 (G5A-237P) to a low-pass filter network,
then passed through antenna switching relay RL1003
(G5A-237P) and another low-pass filter network to the
ANT jack.
28 MHz Signal
The adjusted speech signal from Q1054 is passed through
transistor switch Q1086 (BU4066BCFV) to varactor di-
ode D1093 (HVC300A),which frequency modulates the
transmitting VCO,made up of TX50-29-VCO Q1118
(2SC5374) and D1094 (HSC277).
The modulated transmit signal is passed through buffer
amplifier Q1119 (2SC5374) to the pre-Drive amplifier
Q1123 (2SC5374).
The amplified transmit signal from Q1123 is passed
through diode switches D1127 (DAN235E) and D1142
(HSC277) and driver amplifier Q1137 (2SK2975) to di-
ode switch D1132 (D1F20), then finally amplified by pow-
er amplifier Q1134 (RD70HVF1) up to 50 Watts of output
power. There three stages of the power amplifier’s gain
are controlled by the APC circuit.
The 50-Watt RF signal is passed through antenna switch-
ing relay RL1002 (G5A-237P) to a low-pass filter network,
then passed through antenna switching relay RL1003
(G5A-237P) and another low-pass filter network to the
ANT jack.
APC (Automatic Power Control) Circuit
430 MHz
A portion of the power amplifier output is rectified by
D1103 and D1105 (both MA2S728) then delivered to APC
Q1130 (NJM2904V), as a DC voltage which is proportional
to the output level of the power amplifier.
At Q1130,the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1139
(2SK5396), driver amplifier Q1137 (2SK2975),and pow-
er amplifier Q1134 (RD70HVF1), so as to maintain stable
output power under varying antenna loading conditions.
144 MHz
A portion of the power amplifier output is rectified by
D1114 and D1115 (both MA2S728) then delivered to APC
Q1130 (NJM2904V), as a DC voltage which is proportional
to the output level of the power amplifier.
At Q1130, the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
the supply voltage to the pre-drive amplifier Q1139
(2SK5396), driver amplifier Q1137 (2SK2975),and pow-
er amplifier Q1134 (RD70HVF1), so as to maintain stable
output power under varying antenna loading conditions.
50 MHz
A portion of the power amplifier output is rectified by
D1119 and D1121 (both MA2S728) then delivered to APC
Circuit Description

8
Q1130 (NJM2904V), as a DC voltage which is proportional
to the output level of the power amplifier.
AtQ1130, the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
supply voltage to the pre-drive amplifier Q1123
(2SK5374), driver amplifier Q1137 (2SK2975),and pow-
er amplifier Q1134 (RD70HVF1), so as to maintain stable
output power under varying antenna loading conditions.
29 MHz
A portion of the Power amplifier output is rectified by
D1120 and D1122 (both MA2S728) then delivered to APC
Q1130 (NJM2904V), as a DC voltage which is proportional
to the output level of the power amplifier.
At Q1130, the rectified DC voltage from the power am-
plifier is compared to the reference voltage from the main
CPU Q1084 to produce a control voltage, which regulates
supply voltage to the pre-drive amplifier Q1123
(2SK5374), driver amplifier Q1137 (2SK2975),and pow-
er amplifier Q1134 (RD70HVF1), so as to maintain stable
output power under varying antenna loading conditions.
PTT (Push to Talk) Circuit
430 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
(M38223E4HP) goes “high,” which sendsthe “PTT” com-
mand to main CPU Q1084.
When the “PTT” command is received, the main CPU con-
trolsthe I/O IC Q1075 (BU2090FS), causing pin 12 of
Q1075 to go “low” which activatesthe UHF TX switch
section of Q1076 (IMT17).
When the UHF TX switch section of Q1076 is activated, it
controls the antenna switch diodes D1102, D1104, and
D1146 (all UM9957F), modulator switching diode D1100
(DAN222),modulatorswitchingICQ1051(BU4066BCFV),
diode switches D1073 (HSC277), D1128 (DAN235E),
D1140 (HSC277), and D1134 (HSC277), and APC switch-
es Q1128 (RT1N441U) and Q1129 (RT1P441U), which ac-
tivate the 430 MHz transmitter circuit.
144 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
(M38223E4HP) goes “high,” which sendsthe “PTT” com-
mand to main CPU Q1084.
When the “PTT” command is received, the main CPU con-
trolsthe I/O IC Q1075 (BU2090FS), causing pin 13 of
Q1075 to go “low” which activatesthe VHF TX switch
section of Q1076 (IMT17).
When the VHF TX switch section of Q1076 is activated, it
controlsthe antenna switching relay RL1001 (G5A-237P),
modulator switching diode D1100 (DAN222), modulator
switching IC Q1051 (BU4066BCFV), diode switches
D1075 (HSC277), D1128 (DAN235E), D1139 (HSC277),
and D1133 (RSL135), and APC switches Q1128
(RT1N441U) and Q1129 (RT1P441U), which activate the
144 MHz transmitter circuit.
50 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
(M38223E4HP) goes “high,” which sendsthe “PTT” com-
mand to the main CPU Q1084.
When the “PTT” command is received, the main CPU con-
trolsthe I/O IC Q1075 (BU2090FS), causing pin 14 of
Q1075 to go “low” which activatesthe TX50 switch sec-
tion of Q1077 (IMT17).
When the TX50 switch section of Q1076 is activated, it con-
trols the antenna switching relayRL1002 (G5A-237P), mod-
ulator switching diodeD1092 (DAN222), modulator switch-
ing IC Q1086 (BU4066BCFV), diode switches D1127
(DAN235E),D1141(HSC277),andD1132 (D1F20),andAPC
switches Q1128 (RT1N441U) and Q1129 (RT1P441U),
which activate the 50 MHz transmitter circuit.
28 MHz
When the PTT switch is pressed, pin 8 of sub CPU Q2001
(M38223E4HP) goes “high,” which sendsthe “PTT” com-
mand to the main CPU Q1084.
When the “PTT” command is received, the main CPU con-
trolsthe I/O IC Q1075 (BU2090FS), causing pin 15 of
Q1075 to go “low” which activatesthe TX29 switch sec-
tion of Q1077 (IMT17).
When the TX29 switch section of Q1076 is activated, it con-
trols the antenna switching relayRL1003 (G5A-237P), mod-
ulator switching diodeD1092 (DAN222), modulator switch-
ing IC Q1086 (BU4066BCFV), diode switches D1127
(DAN235E),D1142(HSC277),andD1132 (D1F20),andAPC
switches Q1128 (RT1N441U) and Q1129 (RT1P441U),
which activate the 28 MHz transmitter circuit.
PLL Circuit
“Left” band
A portion of the output from UHF-VCO/A Q1112
(2SC5006) is passed through buffer amplifier Q1113
(2SC5374) and diode switch D1084 (HSC277) to the pro-
grammable divider section of the PLL IC Q1095
(MB15A02PFV1), where it is divided according to the fre-
quency dividing data associated with the operating fre-
quency input from the main CPU Q1084. It is then sent to
the phase comparator.
A portion of the output from the VHF-VCO/A Q1115
(2SC5374) is passed through buffer amplifier Q1116
(2SC5374) and diode switch D1089 (HSC277) to the pro-
grammable divider section of the PLL IC Q1095, where it
Circuit Description

9
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
A portion of the output from the TX50-29-VCO Q1118
(2SC5374) is passed through buffer amplifier Q1119
(2SC5374) and diode switch D1096 (HSC277) to the pro-
grammable divider section of the PLL IC Q1095, where it
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
A portion of the output from the RX50-29-VCO Q1121
(2SC5374) is passed through buffer amplifier Q1122
(2SC5374) and diode switch D1096 to the programmable
divider section of the PLL IC Q1095, where it is divided
according to the frequency dividing data associated with
the operating frequency input from the main CPU Q1084.
It is then sent to the phase comparator.
The 11.15 MHz reference oscillator X1003 frequency is
divided by the reference frequency divider section of
Q1095 into 2230 or 1784 parts,to become 5 kHz or 6.25
kHz comparative reference frequencies, which are utilized
by the phase comparator.
The phase comparator section of Q1095 compares the
phase between the frequency-divided oscillation frequen-
cy of the VCO circuit and the comparative frequency,and
its output is a pulse corresponding to the phase differ-
ence. This pulse is integrated by the charge pump consist-
ing of D1067 (UDZS5.1B), Q1098 (2SA1774), Q1099
(2SC4617),and loop filter into a control voltage (VCV) to
control the oscillation frequency of the VCOs.
“Right” band
A portion of the output from the UHF-VCO/B Q1106
(2SC5006) is passed through buffer amplifier Q1107
(2SC5006) and diode switch D1079 (HSC277) to the pro-
grammable divider section of the PLL IC Q1090
(MB15A02PFV1), where it is divided according to the fre-
quency dividing data associated with the operating fre-
quency input from the main CPU Q1084. It is then sent to
the phase comparator.
A portion of the output from the VHF-VCO/B Q1109
(2SC5374) is passed through buffer amplifier Q1110
(2SC5374) and diode switch D1080 (HSC277) to the pro-
grammable divider section of the PLL IC Q1090, where it
is divided according to the frequency dividing data asso-
ciated with the operating frequency input from the main
CPU Q1084. It is then sent to the phase comparator.
The 11.70 MHz reference oscillator X1002 frequency is
divided by the reference frequency divider section of
Q1090 into 2340 or 1872 parts to become 5 kHz or 6.25
kHz comparative reference frequencies, which are utilized
by the phase comparator.
The phase comparator section of Q1090 compares the
phase between the frequency-divided oscillation frequen-
cy of the VCO circuit and the comparative frequency,and
its output is a pulse corresponding to the phase differ-
ence. This pulse is integrated by the charge pump consist-
ing of D1061 (UDZS5.1B), Q1091 (2SA1774), Q1092
(2SC4617),and loop filter into a control voltage (VCV) to
control the oscillation frequency of the VCOs.
Power Supply Line
When the user presses and holds in the “Left” VOL knob
for 2 seconds, pin 23 of the main CPU Q1084 goes “low”
and pin 39 of main CPU Q1084 goes “high,” which acti-
vatesthe power switch Q1057 (2SB1301), Q1061
(2SC4617), and Q1062 (2SA1774),to supply 13.8 VDC to
each circuit in the transceiver.
Circuit Description

10
Note