Yaesu FT-7900R Manual

FT-7900R/E Technical Supplement
Dual Band FM Transceiver
FT-7900R/E
Technical Supplement
Introduction
This manual provides technical information necessary for servicing the FT-7900R/E 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 dam-
age 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 ................................................ A-1
Exploded View & Miscellaneous Parts ..... B-1
Block Diagram................................................C-1
Circuit Description ....................................... D-1
Alignment ....................................................... E-1
Contents
Board Unit (Schematics, Layouts & Parts)
MAIN Unit ................................................. F-1
PANEL Unit ............................................. G-1
CH Unit ..................................................... H-1
©2011 VERTEX STANDARD CO., LTD. EH016M93B
Important Note
The transceiver was assembled using Pb (lead) free solder, based on the RoHS specification.
Only lead-free solder (Alloy Composition: Sn-3.0Ag-0.5Cu) should be used for repairs performed on this appara-
tus. The solder stated above utilizes the alloy composition required for compliance with the lead-free specifica-
tion, and any solder with the above alloy composition may be used.
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 UK LTD.
Unit 12, Sun Valley Business Park, Winnall Close
Winchester, Hampshire, SO23 0LB, U.K.
VERTEX STANDARD HK LTD.
Unit 1306-1308, 13F., Millennium City 2, 378 Kwun Tong Road,
Kwun Tong, Kowloon, Hong Kong
VERTEX STANDARD (AUSTRALIA)PTY., LTD.
Tally Ho Business Park, 10 Wesley Court, East Burwood, VIC, 3151

FT-7900R/E Technical Supplement
Specifications
A-1
General
Frequency Range: RX: 108.000 - 520.000 MHz,
700.000 - 999.990 MHz (USA: Cellular Blocked)
TX: 144.000 - 148.000 MHz or 144.000 - 146.000 MHz,
430.000 - 450.000 MHz or 430.000 - 440.000 MHz
Channel Steps: 5/10/12.5/15/20/25/50/100 kHz
Modes of Emission: F3E, F2D, F2A
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: 8.5 A (144 MHz, 50 W)
9 A (430 MHz, 45 W)
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 (144 MHz)
45/20/10/5 W (430 MHz)
Modulation Type: Variable Reactance
Maximum Deviation: ±5 kHz, ±2.5 kHz
Spurious Radiation: At least –60 dB below
Microphone Impedance:2kΩ
DATA Jack Impedance: 10 kΩ
Receiver
Circuit Type: Double-conversion superheterodyne
Intermediate Frequencies: 45.05 MHz/450 kHz
Sensitivity: 0.8 µV (TYP) for 10 dB SN (108 - 137 MHz, AM)
0.2 µV for 12 dB SINAD (137 - 150 MHz, FM)
0.25 µV for 12 dB SINAD (150 - 174 MHz, FM)
0.3 µV (TYP) for 12 dB SINAD (174 - 222 MHz, FM)
0.25 µV (TYP) for 12 dB SINAD (222 - 300 MHz, FM)
0.8 µV (TYP) for 10 dB SN (300 - 336 MHz, AM)
0.25 µV for 12 dB SINAD (336 - 420 MHz, FM)
0.2 µV for 12 dB SINAD (420 - 520 MHz, FM)
0.4 µV (TYP) for 12 dB SINAD (800 - 900 MHz, FM)
0.8 µV (TYP) for 12 dB SINAD (900 - 999.99 MHz, FM) (USA: Cellular Blocked)
Squelch Sensitivity: Better than 0.16 µV
Selectivity (–6dB/–60dB): 12 kHz/30 kHz
Maximum AF Output: 2 W @ 8 Ωfor 10% THD
AF Output Impedance: 4-16 Ω
Specifications are subject to change without notice, and are guaranteed within the 144 and 430 MHz amateur bands only. Frequency
ranges will vary according to transceiver version; check with your dealer.

B-1FT-7900R/E Technical Supplement
Exploded View & Miscellaneous Parts
M2090034A
FAN
P1090984
CONNECTOR (USA)
RA0552200
LCD SPACER
RA0540800
LCD HOLDER
G6090155
LCD
RA1110800
RUBBER KNOB
RA0540700
LIGHT GUIDE
RA0551900
REFLECTOR SHEET
RA0540900
INTER CONNECTOR
RA1111300
FRONT PANEL ASSY
(W/ WINDOW, DOUBLE FACE TAPE)
RA1118000
KNOB
RA1121500
ENCODER KNOB
RA1110900
KNOB
Q9000816
ROTARY ENCODER (W/ HEX NUT*, WASHER*)
RA0551800
DIFFUSER SHEET
CH UNIT
PANEL UNIT
RA1118000
KNOB
S5000288
FAN GUARD
M4090207
SPEAKER
T9206438A
WIRE ASSY
R0150630
HOLDER
RA02132A0
HIMERON TAPE
RA0438700
RUBBER
RA02668BA
CHASSIS
RA111070A
REAR PANEL ASSY
(W/ COIL SPRING, RELEASE KNOB)
RA0540400
RELEASE KNOB
RA0022900
COIL SPRING
T9101536
CT CABLE
RA053980A
SUB PANEL
CS1804001
CASE (W/ NYLON NET)
RA0322600
RUBBER SHEET
T9207482 (USA, EXP, AUS)
T9207483 (CE)
WIRE ASSY
RA0415200 (x2 pcs)
GROUND PLATE
P1090547
CONNECTOR (CE, EXP, AUS)
S5000236
WASHER (CE, EXP, AUS)
P1091107
CONNECTOR
T9207057
WIRE ASSY











































*
*
Non-designated parts are available only
as part of a designated assembly.
MAIN UNIT
SUPPLIED ACCESSORIES
VXSTD P/N DESCRIPTION
AAA43X001 MIC MH-48A6J
Q0000081 FUSE 15A (x2 pcs, USA, EXP, AUS Version)
Q0000172 FUSE 15A (x2 pcs, CE Version)
T9021715 DC CABLE (USA, EXP, AUS Version)
T9026115 DC CABLE (CE Version)
R8139500A
LABEL
R8139500A
LABEL
SCREW LIST
No. VXSTD P/N DESCRIPTION QTY.
U31208007 OVAL HEAD SCREW M2.6X8B 8
U44308002 TAPTITE SCREW M3X8NI 17
U03310002 SEMS SCREW ASM3X10NI 4
U20308002 BINDING HEAD SCREW M3X8NI 2
U25320007 TAPTITE SCREW M3X20B 4
U23116007 TAPTITE SCREW M2X16B 5
U31206007 OVAL HEAD SCREW M2.6X6B 6

B-2 FT-7900R/E Technical Supplement
Note
Exploded View & Miscellaneous Parts

C-1FT-7900R/E Technical Supplement
Block Diagram

C-2 FT-7900R/E Technical Supplement
Note
Block Diagram

FT-7900R/E Technical Supplement
Circuit Description
VHF Reception
The incoming VHF signal is passed through a low-pass
filter network, antenna switching diodes D1074 (RLS135),
D1075 (RLS135) and D1015 (HVC131), and another low-
pass filter network to the RF amplifier Q1008 (3SK296ZQ).
The amplified RF signal is passed through a varactor con-
trolled bandpass filter consisting of L1017, L1018, and
D1010, D1011, and D1012 (all HVC365), then applied to
the first mixer Q1009 (3SK296ZQ) along with the first
local signal from the PLL circuit.
The first local signal is generated between 189.05 MHz
and 191.05 MHz, depending on the receiving frequency,
by the VHF VCO, which consists of Q1076 (2SC5374) and
varactor diodes D1049 (HVC365), D1050 (HVC131),
D1051 (HVC365), and D1052 (HVC362).
UHF Reception
The incoming UHF signal is passed through a low-pass
filter network, antenna switching diodes D1077
(MA4P1250) and D1018 (RLS135), D1019 (RLS135), and
D1084 (HSC277), and another low-pass filter network to
the RF amplifier Q1001 (3SK296ZQ). The amplified RF
signal is passed through a varactor-controlled band-pass
filter consisting of L1006 and L1007, and D1002, D1003,
and D1004 (all HVC350B), then applied to the first mixer
Q1002 (3SK296ZQ) along with the first local signal from
the PLL circuit.
The first local signal is generated between 384.95 MHz
and 394.95 MHz, depending on the receiving frequency,
by the UHF VCO, which consists of Q1072 (2SC5006)
and varactor diodes D1046 (HVC375B) and D1047
(HVC350B).
IF and Audio Circuits
The 45.05 MHz first IF signal is applied to the monolithic
crystal filter XF1001 which strips away unwanted mixer
products, and the IF signal is applied to the first IF ampli-
fier Q1016 (2SC4400). The amplified first IF signal is then
delivered to the FM IF subsystem IC Q1023 (TA31136FN),
which contains the second mixer, limiter amplifier, noise
amplifier, and FM detector.
The 44.6 MHz second local signal is derived from 11.15
MHz crystal X1002, the frequency of which is multiplied
by four at Q1022 (2SC4400), producing the 450 kHz sec-
ond IF signal when mixed with the first IF signal within
Q1023 (TA31136FN).
The 450 kHz second IF signal is applied to the ceramic
filter CF1001 which strips away all but the desired shig-
nal, and then passes through the limiter amplifier within
Q1023 (TA31136FN) to the ceramic discriminator CD1001
which removes any amplitude variations in the 450 kHz
IF signal before detection of speech.
The detected audio passes through the de-emphasis net-
work, a low-pass filter consisting of Q1028 (NJM2902V)
and associated circuitry, and a high-pass filter consisting
of Q1028 (NJM2902V) and associated circuitry. The fil-
tered audio signal is passed through the audio volume
control IC Q1034 (M51132FP) which adjusts the audio
sensitivity to compensate for audio level variations, then
delivered to the audio switch Q1036 (DTC144EE).
Squelch Control
When no carrier received, noise at the output of the de-
tector stage in Q1023 (TA31136FN) is amplified and band-
pass filtered by the noise amp section of Q1023
(TA31136FN). The resulting DC voltage is applied to pin
2 of main CPU Q1065 (M3826AEFGP), which compares
the squelch threshold level to that which set by the front
panel SQL knob.
While no carrier is received, pin 53 of Q1065
(M3826AEFGP) remains “low,” to disable audio output
from the speaker.
Transmit Signal Path
The speech signal from the microphone passes through
the MIC jack J2001 to AF amplifier Q2011 (NJM2904V)
on the PANEL unit. The amplified speech signal is sub-
jected to amplitude limiting by Q1040 (NJM2902V) on
the MAIN unit. The speech signal then passes through
low-pass filter network Q1040 (NJM2902V) and band
switch Q1039 (BU4066BCFV) to the VHF VCO or UHF
VCO.
VHF Transmit Signal Path
The adjusted speech signal from Q1040 (NJM2902V) is
delivered to VHF VCO Q1076 (2SC5374) which frequen-
cy modulates the transmitting VCO made up of D1049
(HVC365). The modulated transmit signal passes through
buffer amplifiers Q1077 and Q1078 (both 2SC5374). The
amplified transmit signal is then applied to the Pre-Drive
amplifier Q1084 (RQA0004PXDQS) and Driver amplifi-
er Q1086 (RD07MVS1), then finally amplified by Power
amplifier Q1087 (RD70HVF1) up to 50 Watts. This three-
stage power amplifier’s gain is controlled by the APC cir-
cuit. The 50 Watt RF signal passes through high-pass fil-
ter and low-pass filter network, antenna switch D1072 and
D1073 (both L709CER), and another low-pass filter net-
work, and then is delivered to the ANT jack.
D-1

FT-7900R/E Technical Supplement
UHF Transmit Signal Path
The adjusted speech signal from Q1040 (NJM2902V) is
delivered to UHF VCO Q1072 (2SC5006) which frequen-
cy modulates the transmitting VCO made up of D1046
(HVC375B). The modulated transmit signal passes
through buffer amplifiers Q1073, Q1074, and Q1075 (all
2SC5006). The filtered transmit signal is then applied to
the Pre-Drive amplifier Q1084 (RQA0004PXDQS) and
Driver amplifier Q1086 (RD07MVS1), then finally ampli-
fied by Power amplifier Q1087 (RD70HVF1) up to 40
Watts. This three-stage power amplifier’s gain is con-
trolled by the APC circuit. The 40 Watt RF signal passes
through high-pass filter and low-pass filter networks,
antenna switch D1077 (MA4P1250), and another low-pass
filter network, and then is delivered to the ANT jack.
TX APC Circuit
A portion of the power amplifier output is rectified by
D1070 and D1071 (UHF: D1078 and D1079, all
MA2S728), then delivered to APC Q1081 (NJM2904V),
as a DC voltage which is proportional to the output level
of the power amplifier. The APC Q1081 (NJM2904V) com-
pares the rectified DC voltage from the power amplifier
and the reference voltage from the main CPU Q1065
(M3826AEFGP), to produce a control voltage, which reg-
ulates supply voltage to the Pre-Drive amplifier Q1084
(RQA0004PXDQS), Drive amplifier Q1086 (RD07MVS1)
and Power amplifier Q1087 (RD70HVF1), so as to main-
tain stable output power under varying antenna loading
conditions.
Circuit Description
PTT Circuit
When the PTT switch is pressed, pin 8 of sub CPU Q2001
(M38223) goes “high”, which send the “PTT” command
to main CPU Q1065 (M3826AEFGP). When the CPU re-
ceives the “PTT” command, it engages Q1057 (UMA8N)
and Q1058 (IMT17), which activates the Tx circuit.
PLL Circuit
A portion of the output from the VCO Q1076 (2SC5374)
and Q1072 (2SC5006), passes through the programma-
ble divider section of the PLL IC Q1070 (MB15A02PFV1),
which divides the VCO frequency according to the fre-
quency dividing data that is associated with the current
frequency input from the main CPU Q1065
(M3826AEFGP). It is then sent to the phase comparator.
The 11.15 MHz frequency of the reference oscillator cir-
cuit derived from X1002 is divided by the reference fre-
quency divider section of Q1070 (MB15A02PFV1) into
4250 or 3400 parts to become 5 kHz or 6.25 kHz compar-
ative reference frequencies, which are utilized by the phase
comparator. The phase comparator section of Q1070
(MB15A02PFV1) compares the phase between the fre-
quency-divided oscillation frequency of the VCO circuit
and the comparative frequency and its output is a pulse
corresponding to the phase difference. This pulse is inte-
grated by the charge pump and loop filter of Q1070
(MB15A02PFV1) into a control voltage (VCV) to control
the oscillation frequency of the VCOs.
D-2

FT-7900R/E Technical Supplement
Alignment
Introduction and Precautions
The FT-7900R/E has been carefully aligned at the factory
for the specified performance across the 144 MHz and 430
MHz amateur bands. Realignment should therefore not
be necessary except in the event of a component failure.
All component replacement and service should be per-
formed only by an authorized Vertex Standard represen-
tative, or the warranty policy may be voided.
The following procedures cover the sometimes critical and
tedious adjustments that are not normally required once
the transceiver has left the factory. However, if damage
occurs and some parts are replaced, realignment may be
required. If a sudden problem occurs during normal op-
eration, it is likely due to component failure; realignment
should not be done until after the faulty component has
been replaced.
We recommend that servicing be performed only by au-
thorized Vertex Standard service technicians who are ex-
perienced with the circuitry and fully equipped for re-
pair and alignment. Therefore, if a fault is suspected, con-
tact the dealer from whom the transceiver was purchased
for instructions regarding repair. Authorized Vertex Stan-
dard service technicians realign all circuits and make com-
plete performance checks to ensure compliance with fac-
tory specifications after replacing any faulty components.
Those who do undertake any of the following alignments
are cautioned to proceed at their own risk. Problems
caused by unauthorized attempts at realignment are not
covered by the warranty policy. Also, Vertex Standard
must reserve the right to change circuits and alignment
procedures in the interest of improved performance, with-
out notifying owners.
Under no circumstances should any alignment be attempt-
ed unless the normal function and operation of the trans-
ceiver are clearly understood, the cause of the malfunc-
tion has been clearly pinpointed and any faulty compo-
nents replaced, and the need for realignment determined
to be absolutely necessary.
Required Test Equipment
The following test equipment (and thorough familiarity
with its correct use) is necessary for complete realignment.
Correction of problems caused by misalignment result-
ing from use of improper test equipment is not covered
under the warranty policy. While most steps do not re-
quire all of the equipment listed, the interactions of some
adjustments may require that more complex adjustments
be performed afterwards. Do not attempt to perform only
a single step unless it is clearly isolated electrically from
all other steps. Have all test equipment ready before be-
ginning, and follow all of the steps in a section in the or-
der presented.
Regulated DC Power Supply: adjustable from 11.5 to
16 VDC, 10 A
RF Signal Generator with calibrated output level at
500 MHz
Frequency Counter: ±0.1 ppm accuracy at 500 MHz
AF Signal Generator
SINAD Meter
Oscilloscope
Spectrum Analyzer
Deviation Meter (linear detector)
AF Millivoltmeter
AF Dummy Load: 8-Ohm, 5 W
DC Voltmeter: high impedance
Inline Wattmeter with 5% accuracy at 500 MHz
50-Ohm non-reactive Dummy Load: 50 watts at 500 MHz
VHF/UHF Sampling Coupler
Set up the test equipment as shown below, and apply 13.8
VDC power to the transceiver.
E-1
Power Supply
13.8 VDC
Pin 5
EXT SP
Frequency
Counter
Deviation
Meter
Inline
Wattmeter
50-ohm
Dummy Load
RF Sampling
Coupler
RF Signal
Generator
8-ohm
Dummy Load
SINAD
Meter
AF Signal
Generator

FT-7900R/E Technical Supplement
Alignment
Alignment Preparation & Precautions
A dummy load and inline wattmeter must be connected
to the main antenna jack in all procedures that call for
transmission, except where specified otherwise. Correct
alignment is not possible with an antenna. After complet-
ing one step, read the following step to determine wheth-
er the same test equipment will be required. If not, re-
move the test equipment (except dummy load and watt-
meter, if connected) before proceeding.
Correct alignment requires that the ambient temperature
in the repair shop be the same as that of the transceiver
and test equipment, and that this temperature be held
constant between 20 °C and 30 °C. When the transceiver
is brought into the shop from hot or cold air it should be
allowed some time for thermal equalization with the en-
vironment before alignment. If possible, alignments
should be made with oscillator shields and circuit boards
firmly affixed in place. Also, the test equipment must be
thoroughly warmed up before beginning.
Notes: Signal levels in dB referred to in alignment are
based on 0 dBµ = 0.5 µV (closed circuit).
Entering the Alignment mode
Alignment of the FT-7900R/E is performed using a front-
panel software-based procedure. To perform alignment
of the transceiver, it must first be placed in the “Align-
ment Mode,” in which the adjustments will be made and
then stored into memory.
To enter the Alignment mode:
1. Press and hold in the [MHz(PRI)] key while turning
the radio on.
2. Rotate the DIAL konb so select menu “F-8 NOR/CH.”
3. Press and hold in the [BAND(SET)] key for 1/2 sec-
ond. The radio is turned off automatically, and then
switched on again afterwards.
4. Press and hold in the [PWR()] switch for 1/2 sec-
ond to turn the radio off.
5. Press and hold in the [V/M(MW)] key while turning
the radio on. The display
will be show in the illus-
tration at the right.
6. Press and hold in the [PWR()] switch for 1/2 sec-
ond to turn the radio off.
7. Press and hold in the [MHz(PRI)] key and the Hyper
Memory [5]key while turning the radio on.
8. Press the front panel keys in the following sequence.
[MHz(PRI)] [TONE(HM/RV)] [LOW(ACC)] 
[BAND(SET)] [V/M(MW)] 
[SCAN(SEL)] [S.SCH(ARTS)]
9. Press and hold in the [ (L)] key to cause “A-0 REF.xxH”
to appear on the display, this signifies that the trans-
ceiver is now in the “Alignment mode.”
PLL Reference Frequency
1. Rotate the DIAL knob to set the display to “B4006”,
then set the Transmit Power Level to “LOW” by press-
ing the [LOW(ACC)] key repeatedly.
2. Press the [BAND(SET)] key while pressing and hold-
ing in the [ (L)] key, if needed, to set the Alignment
parameter to “A-0 REF.xxH”.
3. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding the
[ (L)] key, if needed, so that the counter frequency
reading is 435.050 MHz (±100 Hz).
RF Front-end Tuning
1. Connect the DC voltmeter to TP1010 on the MAIN
Unit, then inject a 439.050 MHz signal at a level of +10
dBµ (with 1 kHz modulation @±3.5 kHz deviation)
from the RF Signal Generator.
2. Rotate the DIAL knob to set the display to “B4906”.
3. Press the [BAND(SET)] key while pressing and hold-
ing the [ (L)] key to set the Alignment parameter to
“A-1 TUN.xxH”.
4. Adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the DC voltmeter
reaches maximum deflection. The FT-7900R/E’s RF
Front-end has a broad bandwidth.
5. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0106”.
6. Inject a 145.050 MHz signal at a level of +10 dBµ (with
1 kHz modulation @±3.5 kHz deviation) from the RF
Signal Generator.
7. Adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the DC voltmeter
reaches maximum deflection. As in the previous sec-
tion, be sure to set the DIAL knob for the center of the
band prior to making this adjustment.
MAIN UNIT TEST POINTS
E-2
TP1010

FT-7900R/E Technical Supplement
Alignment
TX Power Output
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
2. Press the [BAND(SET)] key while pressing and hold-
ing in the [ (L)] key to set the Alignment parameter
to “A-2 PWR.xxH.”
3. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 5 Watts (±0.5 Watt).
4. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “MID2”.
5. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 10 Watts (±0.5 Watt).
6. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “MID1.”
7. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 20 Watts (±0.5 Watt).
8. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “HIGH.”
9. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 45 Watts (±0.5 Watt).
10. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0206”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
11. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while press and holding the
[ (L)] key, as needed, so that the wattmeter reading
is 5 Watts (±0.5 Watt).
12. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “MID2.”
13. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 10 Watts (±0.5 Watt).
14. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “MID1.”
15. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 20 Watts (±0.5 Watt).
16. Press the [LOW(ACC)] key to increase the Transmit
Power Level to “HIGH.”
17. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the wattmeter read-
ing is 50 Watts (±0.5 Watt).
TX Deviation
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
2. Press the [BAND(SET)] key while pressing and hold-
ing in the [ (L)] key to set the Alignment parameter
to “A-3 DEV.xxH.”
3. Inject a 1 kHz audio tone at a level of 80 mV (–20 dBm)
from the Audio Generator.
4. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the deviation meter
reading is 4.5 kHz (±0.2 kHz).
5. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0206”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
6. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding in
the [ (L)] key, if needed, so that the deviation meter
reading is 4.5 kHz (±0.2 kHz).
E-3

FT-7900R/E Technical Supplement
DCS TX Deviation
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
2. Activate the DCS with a “023” DCS code.
1) Press the [TONE(REV)] key until “DCS” appears
on the display.
2) Press and hold in the [BAND(SET)] key for 1/2
second to enter the Set mode.
3) Rotate the DIAL knob to select Menu #9 (DCS.COD).
4) Press the [BAND(SET)] key to enable adjustment
of the selected Menu Item.
5) Rotate the DIAL knob to select “DCS.023”.
6) Press and hold in the [BAND(SET)] key for 1/2
second to save the DCS code.
3. Press the [BAND(SET)] key while pressing and hold-
ing in the [ (L)] key to set the Alignment parameter
to “A-4 DSC.xxH.”
4. Press the PTT switch to activate the transmitter (with
no microphone input), and adjust the DIAL knob while
pressing and holding in the [ (L)] key, if needed, so
that the deviation meter reading is between 0.50 kHz
and 0.60 kHz.
5. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0206”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
6. Activate the DCS with a “023” DCS code.
1) Press the [TONE(REV)] key until “DCS” appears
on the display.
2) Press and hold in the [BAND(SET)] key for 1/2
second to enter the Set mode.
3) Rotate the DIAL knob to select Menu #9 (DCS.COD).
4) Press the [BAND(SET)] key to enable adjustment
of the selected Menu Item.
5) Rotate the DIAL knob to select “DCS.023”.
6) Press and hold in the [BAND(SET)] key for 1/2
second to save the DCS code.
7. Press the PTT switch to activate the transmitter (with
no microphone input), and adjust the DIAL knob while
pressing and holding in the [ (L)] key, if needed, so
that the deviation meter reading is between 0.50 kHz
and 0.60 kHz.
CTCSS TX Deviation
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
2. Activate the CTCSS Encoder with a “100 Hz” tone.
1) Press the [TONE(REV)] key until “ENC DEC” ap-
pears on the display.
2) Press and hold in the [BAND(SET)] key for 1/2
second to enter the Set mode.
3) Rotate the DIAL knob to select Menu #44 (TN FRQ).
4) Press the [BAND(SET)] key to enable adjustment
of the selected Menu Item.
5) Rotate the DIAL knob to select “100.0HZ”.
6) Press and hold in the [BAND(SET)] key for 1/2
second to save the CTCSS tone.
3. Press the [BAND(SET)] key while press and holding
the [ (L)] key to set the Alignment parameter to “A-
5 CTC.xxH.”
4. Press the PTT switch to activate the transmitter (with
no microphone input), and adjust the DIAL knob
while pressing and holding in the [ (L)] key, if
needed, so that the deviation meter reading is between
0.65 kHz and 0.75 kHz.
5. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0206”. Set the Transmit Power
Level to “LOW” by pressing the [LOW(ACC)] key
repeatedly.
6. Activate the CTCSS Encoder with a “100 Hz” tone.
1) Press the [TONE(REV)] key until “ENC DEC” ap-
pears on the display.
2) Press and hold in the [BAND(SET)] key for 1/2
second to enter the Set mode.
3) Rotate the DIAL knob to select Menu #44 (TN FRQ).
4) Press the [BAND(SET)] key to enable adjustment
of the selected Menu Item.
5) Rotate the DIAL knob to select “100.0HZ”.
6) Press and hold in the [BAND(SET)] key for 1/2
second to save the CTCSS tone.
7. Press the PTT switch to activate the transmitter (with
no microphone input), and adjust the DIAL knob while
pressing and holding in the [ (L)] key, if needed, so
that the deviation meter reading is between 0.65 kHz
and 0.75 kHz.
Alignment
E-4

FT-7900R/E Technical Supplement
Center Meter Sensitivity
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”.
2. Press the [BAND(SET)] key while press and holding
the [ (L)] key to set the Alignment parameter to “A-
6 CNTL/V.”
3. Inject a 1 kHz audio tone at a level of +10 dBµ from
the Audio Generator.
4. Press the [LOW(ACC)] key while press and holding
the [ (L)] key.
S-Meter Sensitivity
1. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B5006”.
2. Press the [BAND(SET)] key while press and holding
the [ (L)] key to set the Alignment parameter to “A-
7 SM L/V.”
3. Inject a 440.050 MHz signal at a level of –5 dBµ (with
1 kHz modulation @±3.5 kHz deviation) from the RF
Signal Generator.
4. Press the [LOW(ACC)] key while pressing and hold-
ing in the [ (L)] key.
5. Increase the RF Signal Generator output level to +23
dBµ.
6. Press the [V/M(MW)] key while pressing and holding
in the [ (L)] key.
7. Press the [BAND(SET)] key, then rotate the DIAL knob
to set the display to “B0206”.
8. Inject a 146.050 MHz signal at a level of –5 dBµ (with
1 kHz modulation @±3.5 kHz deviation) from the RF
Signal Generator.
9. Press the [LOW(ACC)] key while pressing and hold-
ing in the [ (L)] key.
10. Increase the RF Signal Generator output level to +23
dBµ.
11. Press the [V/M(MW)] key while pressing and holding
in the [ (L)] key.
Alignment
E-5
DC Voltmeter
1. Set the power supply voltage to 13.8 VDC.
2. Press the [BAND(SET)] key while pressing and hold-
ing in the [ (L)] key to set the Alignment parameter
to “A-8 BAT SC.”
3. Press the [SCAN(SEL)] key.
To close the Alignment mode
1. Press and hold in the [PWR()] switch for 1/2 sec-
ond to turn the radio off.
2. Press and hold in the [MHz(PRI)] key while turning
the radio on.
3. Rotate the DIAL konb so select menu “F-8 NOR/CH.”
4. Press and hold in the [BAND(SET)] key for 1/2 sec-
ond. The radio is turned off automatically, and then
switched on again afterwards with normal operation.

FT-7900R/E Technical Supplement
Alignment
E-6
Note

F-1FT-7900R/E Technical Supplement
MAIN Unit (Lot. 1 ~ 115)
Circuit Diagram
[–4.3 dBµ]
[+1.4 dBµ] [+18.8 dBµ] [+15.5 dBµ]
0.81 V
0.30 V
1.37 V
8.56 V
8.57 V
0.69 V
4.94 V
4.75 V
1.10 V 1.48 V
0.50 V
[+15.9 dBµ]
0.98 V
1.56 V
0.43 V
5.83 V
8.83 V
0.15 V
(+15.8 dBµ)
(+0.8 dBµ)
(–6.2 dBµ)
0.97 V
2.22 V
8.13 V
0.32 V
8.53 V
0.70 V
2.92 V
0.71 V
4.69 V
8.70 V
0.71 V
0.78 V
(–8.6 dBµ)
[–9.2 dBµ]
(3.55 V)
[3.30 V]
(3.25 V)
[3.62 V]
(11.45 V)
[11.23 V]
(12.60 V)
[12.54 V]
(xxx): Freq. = 146.05 MHz
[xxx]: Freq. = 440.05 MHz
(xxx): Freq. = 146.05 MHz
[xxx]: Freq. = 440.05 MHz
45.05 MHz
(+21.6 dBµ)
[+21.0 dBµ]
45.05 MHz
(+12.3 dBµ)
[+11.6 dBµ]
0.83 V
0.13 V
4.94 V
2.22 V
0.82 V 0.71 V
0.11 V
0.23 V
(12.73 V)
[12.76 V]
2.09 V
0.68 V
1.23 V
4.72 V
0.69 V
45.05 MHz
(+23.4 dBµ)
[+22.6 dBµ]
Q1023
Pin 1: 4.79 V
Pin 4: 4.81 V
Pin 8: 0.65 V
Pin 10: 4.81 V
1.89 V
8.65 V
8.17 V
4.67 V
6.68 V
0 V
AM: 3.74 V
1.42 V
AM: 2.03 V
1.10 V
AM: 3.35 V
2.00 V 2.00 V
2.00 V
2.33 V 1.78 V
1.78 V
2.33 V
2.01 V
2.00 V
1.91 V
4.98 V
0.93 V
0.91 V
1.88 V
1.89 V
8.82 V 8.80 V 8.86 V
8.87 V 8.86 V
4.98 V
5.65 V
4.90 V
5.00 V
4.97 V
4.86 V
Q1034
Pin 2: 8.33 V
Pin 14: 8.40 V
Pin 15: 3.57 V
Pin 16: 3.27 V
13.78 V
0 ~ 4.90 V
1.40 V
7.00 V
4.86 V
8.95 V
4.98 V
13.78 V
13.05 V
13.80 V
0.12 V
0.70 V
5.00 V
4.95 V
4.56 V
5.00 V

F-2 FT-7900R/E Technical Supplement
Note
MAIN Unit (Lot. 1 ~ 115)

F-3FT-7900R/E Technical Supplement
MAIN Unit (Lot. 1 ~ 115)
Parts Layout (Side A)
ABCDEFGHI
1
2
3
4
5
6
7
2SA1774 (FR)
(Q1069)
2SB1301 (ZQ)
(Q1043)
2SC4400 (RT4)
(Q1016)
2SC4617 (BR)
(Q1019, 1020, 1029,
1030, 1047, 1064,
1071)
2SC5006 (24)
(Q1003, 1013, 1014,
1074, 1075)
2SC5277 (D2)
(Q1012)
2SC5374 (NA)
(Q1078)
RQA0004PXDQS (PX)
(Q1084)
BU2090FS
(Q1059)
M51132FP
(Q1034)
MB15A022PFV1
(Q1070)
TA31136FN
(Q1023)
BU4066BCFV
(Q1039)
NJM2902V
(Q1040)
DTA144EE (16)
(Q1056, 1062)
DTC144EE (26)
(Q1037, 1038, 1054,
1068)
IMT17 (T17)
(Q1058)
LA4425A
(Q1035)
M3826AEFGP
(Q1065)
NJM78L05 (8C)
(Q1046)
RD70HVF1
(Q1087)
UMA8N (A8)
(Q1055, 1057, 1063)
RD07MVS1
(Q1086)
DA221 (K)
(D1040)
DAN222 (N)
(D1022, 1063)

F-4 FT-7900R/E Technical Supplement
Parts Layout (Side B)
MAIN Unit (Lot. 1 ~ 115)
abcdefghi
1
2
3
4
5
6
7
2SC4400 (RT4)
(Q1022)
2SC4617 (BR)
(Q1017, 1018, 1021,
1041, 1051, 1052)
2SC5006 (24)
(Q1072, 1073)
2SC5374 (NA)
(Q1011, 1076, 1077)
NJM2902V
(Q1028, 1031)
DTA144EE (16)
(Q1082, 1088)
DTC144EE (26)
(Q1032, 1033, 1036,
1042, 1066, 1067,
1079, 1080, 1083)
NJM78L05 (8C)
(Q1049)
2SB1201S
(Q1044)
2SD1664 (DA)
(Q1085)
AT24C256
(Q1053)
NJM2904V
(Q1081)
MM1216ENRE (1C)
(Q1045)
S-80823CNMC
(Q1050)
DA221 (K)
(D1030, 1045)
DAN222 (N)
(D1028, 1037, 1038,
1039, 1056, 1058,
1059)
HZM13NB2 (132)
(D1062)
HZM27WA (27A)
(D1031, 1032)
3SK296ZQ (ZQ)
(Q1001, 1002, 1008,
1009, 1010)

F-5FT-7900R/E Technical Supplement
MAIN Unit (Lot. 116 ~)
Circuit Diagram
[–4.3 dBµ]
[+1.4 dBµ] [+18.8 dBµ] [+15.5 dBµ]
0.81 V
0.30 V
1.37 V
8.56 V
8.57 V
0.69 V
4.94 V
4.75 V
1.10 V 1.48 V
0.50 V
[+15.9 dBµ]
0.98 V
1.56 V
0.43 V
5.83 V
8.83 V
0.15 V
(+15.8 dBµ)
(+0.8 dBµ)
(–6.2 dBµ)
0.97 V
2.22 V
8.13 V
0.32 V
8.53 V
0.70 V
2.92 V
0.71 V
4.69 V
8.70 V
0.71 V
0.78 V
(–8.6 dBµ)
[–9.2 dBµ]
(3.55 V)
[3.30 V]
(3.25 V)
[3.62 V]
(11.45 V)
[11.23 V]
(12.60 V)
[12.54 V]
(xxx): Freq. = 146.05 MHz
[xxx]: Freq. = 440.05 MHz
(xxx): Freq. = 146.05 MHz
[xxx]: Freq. = 440.05 MHz
45.05 MHz
(+21.6 dBµ)
[+21.0 dBµ]
45.05 MHz
(+12.3 dBµ)
[+11.6 dBµ]
0.83 V
0.13 V
4.94 V
2.22 V
0.82 V 0.71 V
0.11 V
0.23 V
(12.73 V)
[12.76 V]
2.09 V
0.68 V
1.23 V
4.72 V
0.69 V
45.05 MHz
(+23.4 dBµ)
[+22.6 dBµ]
Q1023
Pin 1: 4.79 V
Pin 4: 4.81 V
Pin 8: 0.65 V
Pin 10: 4.81 V
1.89 V
8.65 V
8.17 V
4.67 V
6.68 V
0 V
AM: 3.74 V
1.42 V
AM: 2.03 V
1.10 V
AM: 3.35 V
2.00 V 2.00 V
2.00 V
2.33 V 1.78 V
1.78 V
2.33 V
2.01 V
2.00 V
1.91 V
4.98 V
0.93 V
0.91 V
1.88 V
1.89 V
8.82 V 8.80 V 8.86 V
8.87 V 8.86 V
4.98 V
5.65 V
4.90 V
5.00 V
4.97 V
4.86 V
Q1034
Pin 2: 8.33 V
Pin 14: 8.40 V
Pin 15: 3.57 V
Pin 16: 3.27 V
13.78 V
0 ~ 4.90 V
1.40 V
7.00 V
4.86 V
8.95 V
4.98 V
13.78 V
13.05 V
13.80 V
0.12 V
0.70 V
5.00 V
4.95 V
4.56 V
5.00 V

F-6 FT-7900R/E Technical Supplement
Note
MAIN Unit (Lot. 116 ~)