Icom IC-821H User manual

VHF/UHF
ALL MODE TRANSCEIVER
IC-B21H
learn Inc.

INTRODUCTION
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6,.. 01 pubIicaIion.
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REPAIR NOTES
I. Mak e .",e a p«)blem is i nl em al belo< e d ; salll~ mbl i ng !he
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2. DO I'IOT 0!lI'" t he Uansceiv e' un lil ( he tl an_i,e , is
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3. 00 NOT fon::e....,.,.. 0I1he ,ariab!e 00I';"',,,_ •• ,1S. T um 1I>em
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-- 7. A~WA VS connec! a 50 dB10 eo dB aHenualo< be :.. e,,,
!hetr..-..ceivet and adeviatioomelet Ot specltvm~ ..
_ using suc/11e51 equipment .
8. READ the instn>el ioo. 01 t e& 1equiprl'le nl V \C<O\9" ~ before
connec ti 11\1 equi pment to lloe tr ansceiver.

TABLE OF CONTENTS
SECTION 1 SPECIFICATIONS
SECTION 2 DISASSEMBLY INSTRUCTIONS
SECTION 3 INSIDE VIEWS
SECTION 4 CIRCUIT DESCRIPTION
4 - 1 RECEIVER CIRCUITS ...................................................................................................................................4 - 1
4 - 2 TRANSMITTER CIRCUITS ............................................................................................................................4 - 4
4-3 PLLCIRCUITS ............................................................................................................................................... 4-6
4 - 4 POWER SUPPLY CIRCUITS .........................................................................................................................4 - 7
4 - 5 PORT ALLOCATIONS....................................................................................................................................4 - 7
SECTION 5 ADJUSTMENT PROCEDURES
5 -1 PREPARATION BEFORE SERVICING ......................................................................................................... 5-1
5 - 2 PLL ADJUSTMENT ........................................................................................................................................5 - 2
5 - 3 FREQUENCY ADJUSTMENT ........................................................................................................................5 - 2
5 - 4 RECEIVER ADJUSTMENT ............................................................................................................................5 - 4
5 - 5 TRANSMITTER ADJUSTMENT .....................................................................................................................5 - 8
5 - 6 METER AND SQUELCH ADJUSTMENT.....................................................................................................5
-12
5 - 7 RF METER ADJUSTMENT ..........................................................................................................................5 - 13
5 - 8 METER REFERENCE ADJUSTMENT.........................................................................................................5 - 13
SECTION 6 PARTS LIST
SECTION 7 MECHANICAL PARTS
SECTION 8 SEMI-CONDUCTOR INFORMATION
SECTION 9
BOARD LAYOUTS
9 - 1 FRONT ...........................................................................................................................................................9 - 1
9 - 2 MAIN UNIT .....................................................................................................................................................9 - 4
9 - 3 PLL UNIT ........................................................................................................................................................9 - 6
9 - 4 PA-A AND PA-B UNITS .................................................................................................................................9 - 7
9 - 5 RF-A AND RF-B UNITS..................................................................................................................................9 - 8
SECTION 10 BLOCK DIAGRAM
SECTION 11 VOLTAGE DIAGRAM

SECTION 1 SPECIFICATIONS
• GENERAL • RECEIVER
• Frequency coverage:
Version 144 MHz band 440 MHz band
Rx: 136.0-174.0 MHz*
U.S.A 430.0-450.0 MHz
Tx: 144.0-148.0 MHz
Europe
144.0-146.0 MHz 430.0-440.0 MHz
Australia
144.0-148.0 MHz 430.0-450.0 MHz
Sweden
144.0-146.0 MHz 432.0 -438.0 MHz
*Guaranteed frequency range IS
144.0-148.0 MHz
• Mode SSB (J3E), cw (A1A), FM (F3E)
• Number of memory: 160 (80 channels for each band)
channels
• Antenna connector: VHF SO-239 (50 Q)
UHF Type-N (50 Q)
• Usable temperature: -10°C to +60 t : +14 of to +140 of
range
• Frequency stability :
• Tuning steps
• Power supply
requirement
• Current drain
(at 13.8
V)
• Dimensions
• Weight
±3 ppm ( - 10°C to +60°C )
SSB, CW 1,10,50 or 100 Hz
FM 0.1 , 5, 10, 12.5, 20, 25 or
100 kHz
13.8 V ±15 % (negative ground)
Transmit Max. power 16.0 A
Receive Stand-by 2.0 A
Max. audio 2.5 A
241 (W) x 94 (H) x 239 (D) mm
9.5 (W) x 3.7 (H) x 9.4 (D)
in
(projections not included)
5.0 kg; 11.0 Ib
• TRANSMITTER
• Output power 144 MHz SSB
6-35 W
FM, CW 6-45W
440 MHz SSB 6-30 W
FM, CW
6-40W
(continuously adjustable)
• Modulation system : SSB Balanced modulation
FM Variable reactance mod.
• Suprious emission : Less than -60 dB
• Carrier suppression: More than 40 dB
• Unwanted sideband: More than 40 dB
• Microphone 8-pin connector (600 Q)
connector
• Key connector 3-conductor 3.5
(d) mm (1/8")
• Receive system
144 MHz band
SSB, CW
FM
440 MHz band
Single conversion superheterodyne
Double conversion superheterodyne
SSB, CW Double conversion superheterodyne
FM Triple conversion superheterodyne
• Intermediate frequencies (unit: MHz)
MAIN BAND SUB BAND
MODE ~---r----.----4----.-----r---~
1st 2nd 3rd 1st 2nd 3rd
SSB 10.8500 10.9500
IL. .................................................................... .
X
> CW 10.8491 10.9491
... __ .........................................................................................
FM 10.8500 0.4550 10.9500 0.4550
SSB 71.2500 10.8500 71.3500 10.9500
IL. ................................................................... .
X
~
CW 71.2491 10.8491 71.3491 10.9491
FM 71.2500 10.8500 0.4550 71.3500 10.9500 0.4550
• Sensitivity (both VHF and UHF bands)
SSB, CW 0.11 IlV for 10 dB SIN
FM 0.181lV for 12 dB SINAD
• Squelch sensitivity (both VHF and UHF bands)
SSB, CW Threshold Less than 1.0 IlV
Tight Less than 3.2 mV
FM Threshold Less than 0.1 IlV
• Selectivity
SSB, CW
CW narrow
(optional)
FM
• Spurious and image:
rejection ratio
• Audio output power:
(at 13.8 V
DC)
• IF shift variable
range
• RIT variable range
SSB, CW
FM
• External speaker
connector
Tight Less than 3.2 mV
More than 2.3 kHz/-6 dB
Less than 4.2
kHz/- 60 dB
More than 0.5
kHz/-6 dB
Less than 1.34
kHz/- 60 dB
More than 15.0
kHz/- 6 dB
Less than 30.0 kHz/-
60 dB
More than 60 dB
More than 2.0 W at 10 %
distortion with
an 8 Q load
More than ± 1.2 kHz
More than ±1.0 kHz
More than ±5.0 kHz
2-conductor 3.5 (d) mm
(1/8") /8 Q
x 2 (for MAIN and SUB bands)
All stated specifications are subject to change without notice or obligation.
1 -1

SECTION 2 DISASSEMBLY INSTRUCTIONS
• Opening the transceiver's case
CD. Unscrew 8 screws from the transceiver's top and 4 screws
from the sides, then remove the top cover.
® Turn the transceiver upside down.
® Unscrew 4 screws from the bottom cover, then remove the
bottom cover.
• Opening the inside chassis
CD Remove the top and bottom covers as shown above.
® Loosen the gutter screw on each side of the front panel's
rear side.
® Unscrew t screw from each side of the front panel's rear
side.
® Pull the front panel forward as shown by the arrow at right.
® Loosen 1 flat head screw each side of the MAIN unit
chassis.
® Unscrew 2 silver screws from the rear panel.
(j) Lift and pivoted the MAIN unit chassis to the vertical
position, and tighten the screws (labelled ®) to secure the
chassis.
2 -1
• Removing the PA-A unit
CD Opening the inside chassis as previous instructions.
® Unscrew 8 silver screws ®, then remove the PA-A cover.
® Unsolder 3 points ®.
® Unscrew 2 screws ®.
® Unscrew 6 silver screws ®, then remove the PA-A unit.
• Removing the PA-B unit
CD Remove the top cover.
® Unscrew 8 silver screws ®, then remove the PA-B cover.
® Unsolder 3 points ®.
® Unscrew 2 screws ®.
® Unscrew 2 screws ®.
® Unscrew 8 silver screws ®, then remove the PA-B unit.
rv
I

SECTION 3 INSIDE VIEWS
• MAIN UNIT ,
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• RF·A, RF·B AND PA ·B UNITS
,
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• PA·A AND PLL UNITS
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(IC' :SC · 11 14)
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f------- ,~ DDSoO-euil

SECTION 4 CIRCUIT DESCRIPTION
4-1 RECEIVER CIRCUIT
Note: [Main]=Main band, [Sub]=Sub band
4-1-1 VHF ANTENNA SWITCHING CIRCUIT
(PA-A UNIT)
Received signals from the antenna connector (J2) are
passed through the low-pass filter (L3-L5, C5-C8) then
applied to the antenna switching circuit {01-03, L6. L7}.
The antenna switching circuit functions as a low-pass filter
while receiving. However, its impedance becomes very
high while transmitting by turning
ON diodes (02, 03).
Thus transmit signals are blocked from entering the receiver
circuits.
The passed signals are then applied to the RF-A unit.
4-1-2 VHF RF CIRCUIT (RF-A UNIT)
Received signals from the PA-A unit via J6 are applied to
the RF amplifier circuit (Q7) via the RF attenuator (015) and
tunable bandpass filter (013. L16) circuits.
The amplified signals are then passed through the another
tunable bandpass filter circuit (010-012, L
13-L 15) to sup-
press unwanted signals. The filtered signals are then
applied
to the 1st mixer circuit (Qll ,Q12).
Varactor diodes (010-013) are used for the bandpass
filters
to tune the center frequency for wide bandwidth
receiving and good image response rejection. PLL lock
voltages are applied to these diodes for tuning.
4-1-3 VHF 1STMIXER CIRCUIT (RF-A UNIT)
The 1st mixer circuit converts the received signals to a fixed
frequency of the 10
MHz IF signal with a PLL output fre-
quency. By changing the PLL frequency, only the desired
frequency
will be passed through a pair of crystal filters at
the next stage of the VHF 1st mixer.
• RECEIVER CONSTRUCTION
440 MHz PA unit:RF·B unit
014.015
4 -1
The filtered signals from the bandpass filter are mixed with
1st
LO signals at the mixer circuit (Ql1, Q12) to produce a
1st IF signal (10.85
MHz [Main] or 10.95 MHz [Sub]). The
1
st LO signals are the PLL output frequency which comes
from the VHF veo circuit (PLL unit. Q1. 01-03, 08).
The 1st IF signal is then applied to either the Main or Sub
band 10 MHz IF circuit in the MAIN unit via P1 [Main] or P2
{Sub].
4-1-4 UHF RF CIRCUIT (RF-B UNIT)
The received signals from the UHF antenna connector are
passed through the low-pass tilter (PA-B unit, L3-L5,
C5-C10) and then the antenna switching circuit (PA-B unit,
01-03). The signals from the antenna switching circuit are
then applied
to the RF amplifier circuit (Q16) via the tunable
bandpass filter (014,
L35) and RF attenuator circuit {016}.
The amplified signals are passed through the tunable band-
pass filter (011-013),
and then applied ~o the 1 st mixer
circuit (Q14, Q15).
4-1-5 UHF 1STAND 2ND MIXER CIRCUIT
(RF-B UNIT)
The filtered RF signals from the bandpass filter are mixed
with a 1 st LO signal at the 1st mixer circuit (Q14, Q15) to
produce a 1st IF signal (71.25 MHz [Main] or 71.35 MHz
[Sub]). The 1st IF signal is passed through a crystal filter
(F12 [Main), Fll [Sub]) to suppress out-ot-band signals. The
filtered IF signal is then applied to the 2nd mixer circuit
(Qll) to produce a 10 MHz IF signal with a 2nd LO signal.
The IF signal is then applied to the MAIN unit via P1 [Main]
or
P2 [Sub].
The 1st LO signal is generated at the UHF VCO circuit (PLL
unit, Q5, 04, 010), and the multiplied reference signal is
used for the 2nd LO signal.
I MAIN unit
I
I
I
I
BFO
for MAIN band
AF signals to SOL
control circuit
tor SUB band
AF signals to SOL
control circuit
10.9483-10.9515 MHz
to FM IF IC (IC20)

4-1-6 10 MHz IF CIRCUIT (MAIN UNIT)
The 10 MHz IF signal from the mixer circuit is passed
through the bandpass filter (FI2 [Main], FI6 [Sub]) to sup-
press out-of-band signals. The filtered signal is amplified at
the IF amplifier (013 [Main], 098 [Sub]). The IF amplifier
provides 20 dB gain.
The amplified signal
is then applied to different circuits
depending
on the selected mode.
(1)
FM mode
The signal
is applied to an FM IF IC pin 16 (IC11 [Main] or
IC20 [Sub]).
(2) SSB and CW mode
The signal
is passed through a 10 MHz IF filter (FI1 /1 0.85
MHz [Main] or FI5/10.95 MHz [Sub]) or optional CW narrow
filters. The filtered signal is amplified at the IF amplifiers
(060-062 [Main] or 077. 0100. 0101 [Sub]) and then
applied to a demodulator circuit.
4-1-7 DEMODULATOR CIRCUIT (MAIN UNIT)
(1) FM mode
The 10
MHz IF signal from an IF amplifier (013 [Main] or
098 [Sub]) is applied to the mixer section of the FM IF IC
(IC11 [Main], IC20 [Sub). pin 16) and is mixed with a lO
signal (10.395 MHz [Main). 10.495 MHz [Sub]) to produce a
455
kHz IF signal. The lO signal is generated by the BFO
circuit (IC1 01 [Main], IC103 [Sub])
The FM detector circuit employs the quadrature detection
method. which uses a ceramic discriminator
(X2 [Main], X4
[Sub]) for phase delay to obtain a non-adjusting circuit.
The detected signals are output from
pin 9, and applied to
the squelch control
and center indication detector circuits.
etc.
(2) SSB and CW modes
The amplified signal from the IF amplifier circuit (062
[Main]. 0101 [Sub])
is applied to the balanced mixer circuit
(IC14 [Main]. IC22 [Sub]) to demodulate into AF signals.
Demodulated audio signals are output from
pin 3, and
applied to the squelch control gate (IC16 [Main]. IC28
[Sub]).
• AF circuit
IC14
Demodulator
[MAIN band]
BFO circuits (IC101 [Main] and IC103 [Sub]) generate BFO
signals for use in the balanced mixers.
• BFO frequencies
Mode
for MAIN band for SUB band
USB 10.8485 MHz 10.9485 MHz
lSB 10.8515 MHz 10.9515 MHz
CW 10.8483 MHz 10.9483 MHz
4-1-8 SQUELCH CONTROL CIRCUIT
(MAIN UNIT)
The demodulated AF signals from the balanced mixer
circuit or
FM IF IC are applied to the squelch control gate
(IC16 [Main), IC28 [Sub]). This consists of 4 analog
switches which are selected with a mode signal and squelch
control signal from the
CPU (DISPLAY unit, IC1) via the
expander
IC (IC8 [Main], IC24 [Sub]). The switched AF
signals are applied to the AF circuit.
4-1-9 SQUELCH CIRCUIT (MAIN UNIT)
(1) FM mode
A squelch circuit cuts out
AF signals when no RF signal is
received or the S-meter signal is lower than the [SOL]
control setting level.
By detecting noise components in the
AF signals, the CPU switches the squelch control gate.
Some noise components in the AF signals from pin 9 of the
FM IF IC (IC11 [Main], IC20 [Sub]) are applied to the active
filter section
(pin 10) of the FM IF IC. The filtered noise
components are output from pin
11 , and then applied to the
noise detector circuit
(D35 [Main], D55 [Sub]) for conversion
into
DC voltages. The voltages are then applied to the
buffer-amplifier (IC116 [Main], IC118 [Sub]).
The buffer-amplified
DC voltages are applied to the CPU
(DISPLAY unit. IC1) via the ADMNO [Main]/ADSNO [Sub]
line. The [SOL] level signal is also applied to the CPU via
the gate control circuit (DISPLAY unit. IC11)
as a reference
voltage for comparison with the noise signals. Also, an
S-meter signal is applied to the CPU from FM IF IC pin 13
(IC11 [Main], IC20 [Sub] via the meter amplifier (IC15a
[Main], IC23b [Sub]). The CPU compares these signals.
then outputs a control signal to the squelch control gate.
JACK board MSP SSP
AFMM IC32
rnrn
11
------------------------
IC22 [SUB band] 7
Demodulator
AFMS
4-2

(2) SSB and CW modes
The squelch circuit mutes audio output when the S-meter
signal is lower than the [SOL] control setting level.
A portion of the 10 MHz IF signal from the IF amplifier (062
[MainJ. 0101 [Sub]) is converted into DC voltage at the
AGC detector (044. 065 [Main]. 073. 0104 [Sub)) and
meter amplifier (IC15b [Main] or IC23a [Sub)). The ampli-
fied signal is applied to the CPU (DISPLAY unit. IC1) via the
ADMSM [Main]/ADSSM [Subjline. The CPU outputs con-
trol signals to the squelch control gate when the S-meter
signal is low level.
4·1·10 AF AMPLIFIER CIRCUIT (MAIN UNIT)
The AF amplifier circuit amplifies the demodulated signals
to drive a speaker. For the separate speaker function. a
stereo power amplifier
is used.
AF signals from the squelch control gate are amplified at
the voltage controlled amplifier (VCA; IC30 [Main]. IC31
[Sub]) which functions as a volume control using the [AF]
control signal. The amplified AF Signals are applied to the
AF power amplifier circuit (IC32. pin 2 [Main]. pin 5 [Sub]).
The amplified audio signals of SUB band are output from
from pin 7I and are applied to the external speaker jack for
the
SUB band (J17) via the [PHONE] jack (JACK board, Jl).
When no plug is connected to the jack. the signals are fed
back to the MAIN band audio input (IC32, pin 2) and
combined with the MAIN band audio. The mixed audio is
applied to the internal speaker via the [PHONE] jack and
external speaker jack for the MAIN band (J16).
4·1·11 NOISE BLANKER CIRCUIT
(MAIN UNIT)
The noise blanker circuit detects pulse-type noises, and
stops IF amplifier operation during detection.
• AGC and Noise Blanker circuits
FI2 [F16)
IF signal
013
(098) Fl1 [F15)
060
(077)
4-3
A portion of the 10 MHz IF signal from the bandpass filter
(F12 [Main], FI6 [Sub]) is amplified at the noise amplifier
circuit (07. IC6,
09 [Main], 0252, IC119, 0254 [Sub]). The
amplified signal
is rectified at the noise detector circuit for
conversion
Into DC voltage. The DC voltage is amplified at
the DC amplifier circuit (011, 012 [Main], 0256. 0257
[Sub)) and then applied to the noise blanker control circuit
(014
[Main]. 0212 [Sub]) to stop amplification of the IF
amplifier circuit (013 [Main]. 098 [Sub)).
Some DC voltage is fed back to the nOise amplifier circuit
(IC6 [Main]. IC116 [Sub)) via the DC amplifiers (08, 010
[Main]. 0253, 0255 [Sub]). The DC amplifiers function as
an AGC circuit to reduce averaged noise. Therefore. the
noise blanker function shuts off pulse-type noise only.
4-1-12 AGC CIRCUIT (MAIN UNIT)
The AGC (Auto Gain Control) circuit reduces IF amplifier
gain to keep the audio output at a constant level.
A portion of the 10
MHz IF signal from the IF amplifier (062
[MainJ. 0101 [Sub}) is applied to the AGC detector circuit
(044 [Main]. 073 [Sub}). The detected signal is then
amplified
at the DC amplifier circuit (065 [Main]. 0104
[Sub])
and then applied to the IF amplifiers (013. 061. 062
[Main]. 098, 0100, 0101 [Sub]).
When strong signals are received, the detected voltage
increases
and the output level of the DC amplifier, as AGC
voltage, decreases. The AGC voltage is used for the bias
voltage for the IF amplifiers. therefore. the IF amplifier gain
is decreased.
AGC response time is controlled by changing the time
constant
at the AGC control line with a resistor (R276
[Main]. R432 [Sub]) and capacitors (C206. C210 [Main).
C381. C385 [Sub]). These are connected to the AGC
control line While AGC is set to slow. However, R276 and
C210 [Mainj/R432 and C385 are disconnected from the
AGC control line while AGC is set to fast. due to 067 and
068 [Main}/0105 and 0210 [Sub} being switched OFF.
Also, C206 [MainJ/C381 [Sub] is disconnected from the
AGC control line due to 054 and 055 [Main]/0206 and
0207 being switched OFF while scanning for faster re-
sponse than AGC fast mode .
061
(0100)
062 IC7
[0101::;» ----4~~®
demodulator
circuit
AGe amplifier
065 044
[0104] [073]
. iAGC
~ ..... Jdetector
+---------0 -5 V
]: Sub band

4-1-13 S-METER CIRCUIT (MAIN UNIT)
The S-meter circuit indicates the relative received signal
strength while receiving
and changes depending on the
received signal strength.
(1) FM mode
Some of the amplified IF signal is applied to the S-meter
detector section
in the FM IF IC (lC11 [Main), IC20 [Sub)) to
be converted into DC voltage. The converted signal is
output from pin 13 and applied to the meter amplifier circuit
(IC15a [Main), IC23b [Sub)). The amplified signal is then
applied to the CPU (DISPLAY unit, IC1) via the ADMSM
[Main)/ADSSM
[Sub) line. The CPU then outputs S-meter
drive signals as a METO signal.
(2) sse and CW modes
A portion of the AGC control signal is applied to the S-meter
amplifier. The amplified signal
is then applied to the CPU to
drive the S-meter.
4-2 TRANSMITTER CIRCUITS
4-2-1 MICROPHONE AMPLIFIER CIRCUIT
(DISPLAY AND MAIN UNITS)
The microphone amplifier circuit amplifies audio signals
from the microphone or
ACC connector and then applies
them to the modulation circuit. One microphone amplifier
circuit
is commonly used for both FM/SSB and VHF/UHF.
Audio signals from the microphone are amplified at the
variable controlled amplifier (VCA; DISPLAY unit, IC3)
where the amplifier gain is controlled with the [MIG) control
setting.
The mic limiter circuit (029) activates when the
[COMP)
switch is turned ON to limit VCA output. The amplifier gain
is also controlled with the [COMP LEVEL) control in such
cases. The amplified audio signals are then applied to the
other microphone amplifier circuit (IC2a)
in the MAIN unit.
Audio signals from the
ACC connector is amplified at IC2b.
These amplified signals from IC2a or IC2b are applied to
the IDC or the balanced mixer circuit depending on oper-
ating mode.
• SIGNAL CONSTRUCTIONS IN SATELLITE MODE
Example UHF receive / VHF transmit
MAIN band: Rx SUB band: Tx/Rx
433.000.0
VHF UHF I
I
I
lh~
145.000.0
!MAIN unit
I
I
RF-B unit ~-t-""'\
I I
L ~.-.-.-.-.-.-.I
I
4-2-2 MODULATION CIRCUIT (MAIN UNIT)
(1) FM mode
The amplified audio signals from IC2a are pre-emphasized
and limited at IC1 b and then passed through the splatter.
filter
(IC1 a). The filtered signals are then applied to the FM
modulation circuit (022) via the FM deviation adjustment
pot (R29). Also, subaudible tone signals from the BFO
circuit (IC1 01) are applied to the FM modulation circuit via
the tone deviation adjustment pot (R64).
The
FM modulation circuit changes the generating fre-
quency of the FM local oscillator (017, X1) to generate an
FM signal. The modulated IF signal is passed through the
transmit gain control pot (R136)
and then applied to the
transmit IF amplifier circuit.
When 9600 bps mode
is selected, audio signals from the
ACC connector bypass the amplifiers and are applied to 04
directly via the external modulation switch (MAIN unit,
IC114, pins 1, 7). In such cases, the modulation limiter
(IC17) cuts off the audio line when overmodulation
is
detected.
(2) sse mode (MAIN unit)
The amplified audio signals from IC2a are mixed with BFO
signals at the balanced mixer circuit (IC7) to produce a 10
MHz IF signal. The mixed signal is still a DSB signal,
therefore, the mixed signal passes through bandpass filter
circuit (FI1) to suppress unwanted side band signals. The
filtered signal
is applied to the transmit IF amplifier circuit.
Mode
Transmit IF signal
USB 10.8485 MHz
LSB
10.8515 MHz
CW
10.8491 MHz
4-2-3 CW KEYING CIRCUIT (MAIN UNIT)
Keying signals (EDOT and EDSH) from the [KEY) jack (J19)
are applied
to the CPU (DISPLAY unit, IC1), and the CPU
outputs an EKEY signal to the CW break-in circuit (0234,
084). The signal output from the CW break-in circuit is
applied to the BFO mute switches (0120, 0121) to cut the
BFO signal line while releasing. While keying, BFO signals
are applied to the balanced mixer, and a DC bias voltage is
applied to leak carrier signals.
"W....
[SUB VOL)

The output signal from the CW break-in circuit is also
applied
to the CW side-tone generator circuit (Q80, Q81).
4·2·4 TRANSMIT IF AMPLIFIER CIRCUIT
(MAIN UNIT)
The modulated IF signal from a modulation circuit is applied
to the IF amplifier circuit (Q1). The amplified IF signal is
then applied to the RF-A (during VHF) or RF-B (during
UHF) unit via the
V/U switching circuit (018).
The gain of the IF amplifier circuit (Q1) is controlled by the
ALC amplifier circuit (IC3a). Therefore, the IF amplifier is
reduced when the output power increases.
4-2-5 RF CIRCUIT (RF-A AND RF-B UNITS)
The RF circuit consists of mixer and drive amplifiers to
obtain the desired frequency
and level needed at a PA unit,
respectively.
(1) VHF band (RF·A unit)
The IF signal
is mixed with an LO signal from the VHF VCO
circuit (PLL unit, 01, 01-03, 08) at the double-balanced
mixer circuit (01,
02) to be converted into a VHF transmit
frequency. The mixed signal
is then passed through the
tunable bandpass filter (03-05) to suppress spurious com-
ponents, and then amplified at the drive amplifiers (IC1, Q4,
013) to obtain an approx. 800 mW output level.
The amplified RF signal is applied to the PA-A unit via J7.
(2) UHF band (RF·B unit)
The IF signal is mixed with a 2nd LO signal at the double-
balanced mixer circuit (01,
02) to produce a 2nd IF signal
(71.25 MHz). The 2nd LO signal is generated at the
reference oscillator
and multiplier circuit (PLL unit, X1, Q14)
via
LO amplifier (IC2). The 2nd IF signal is amplified at the
buffer amplifier (03) via the bandpass filter circuit
(L3, L4,
C12-C14, C164. C178, C179). The amplified 2nd IF signal
is applied
to the 1 st mixer circuit (IC3).
The 1 st mixer circuit converts the 2nd IF signal into a UHF
transmit frequency
with a 1 st LO Signal from the UHF VCO
circuit (PLL unit. as, 04. 010). The converted RF signal is
amplified at drive amplifiers (IC1. 04, aS) to obtain an
approx. 200 mW output level. The signal is then applied to
the
PA-B unit via J3.
• APC and ALC circuits
..
I
Bandpass filters (L36, L37) are designed between drive
amplifiers to suppress spurious components
in the RF
signal.
4-2-6 POWER AMPLIFIER CIRCUIT
(PA-A AND PA·B UNITS)
The power amplifier circuit amplifies the RF signals to the
specified output power.
(1) VHF
power amplifier circuit (PA-A unit)
The RF signal from the RF-A unit is applied to the power
amplifier circuit (IC2). The amplified RF signal is applied to
the antenna connector
(J2) via the power detector (04-07,
L8), antenna switching (01-03) and low-pass filter (L3-L5,
C5-C8) circuits.
(2) UHF power amplifier
circuit (PA·B unit)
The RF signal from the RF-B unit is applied to the drive
amplifier circuit (IC3) to obtain
4-5 W output level and then
applied to the power amplifier circuit (IC1). The amplified
RF signal is applied to the antenna connector (J1) via the
power detector (04,
OS, L9), antenna switching (01-03)
and low-pass filter (L3-L5, C5-C10) circuits.
4-2-7 ALC CIRCUIT
(PA-A, PA-B AND MAIN UNITS)
The ALC (Automatic Level Control) circuit protects the
power module (PA-A unit, IC2 for VHF and
PA-B unit. IC1
for UHF) from a mismatched output load. Also, the ALC
circuit controls the gain of the transmit IF amplifier in order
for the transceiver to output a constant
RF power set by the
[RF PWRl control even when the supplied voltage shifts,
etc.
The RF power level is detected at the power detector circuit
(PA-A unit,
04-07, L8 for VHF, PA-B unit 04. OS, L9 for
UHF) to be converted into
OC voltages. The detected
voltage (FORA for VHF or FORB for UHF) is applied to the
difference amplifier (MAIN unit, IC3a). A reference voltage
(POCO) for IC3a is controlled by the [RF PWRl control to
output difference voltages. The output voltage is applied to
the transmit IF amplifier circuit (MAIN unit, Q1) as
an AALC
Signal to control the amplifier gain.
to antenna connector
IF
signal I
APC~"""" .........•....... :
I det. i i
I iDS 04:
I ::
I I' - 0::- :Current:
I '0:: ': OS:
I RF·A unit I ~ ......••.•••. .idet. _ ..•••......................
-MAIN- u-;"ii - -'C4b -- ~ ----- -! <
'-- ____ --1~7< APC HVF . ~ PA-A unit
!-------------IC1-f~~ PA.S ------ -u.. --------
I------------+-- FORB from PA·B
1'----"1'111<::-1 [RF PWRl
control
4-5

When the FORA/FORB voltage increased, the output from
the difference amplifier will
be decrease to reduce the IF
amplifier gain. This adjusts the
RF output power until the
FORA/FORB and POCO voltages are well-balanced.
4-2-8 APC CIRCUIT
(PA-A, PA-B AND MAIN UNITS)
The APC (Automatic Power Control) circuit protects the
power amplifiers
on the PA-A and PA-B units from exces-
sive current.
Current drain of power amplifiers
is detected by voltage
drops at resistors (PA-A unit R1, R12 and PA-B unit R1,
R16). The original voltage (IC1) and dropped voltage (AIC2
or BIC2) are applied to the APC difference amplifier (MAIN
unit, IC4a or IC4b).
The signal output from the difference amplifier reduces IF
amplifier gain until these voltages are well-balanced.
4-3 PLL CIRCUITS
IC-821 H contains 2 PLL circuits and 1 local oscillator. The
VHF and UHF PLL circuits adopt "I com's original I-loop
PLL" to obtain very fast lock up times.
• PLL circuits
ICl
IC2a
4-3-1 VHF PLL CIRCUIT (PLL UNIT)
The VHF PLL circuit generates the 1 st LO frequency, and
the signals are applied to the 1st mixer circuits in the RF-A
unit. The PLL circuit consists of a VCO, prescaler
and DDS
circuits.
The signal generated
at the VHF VCO circuit (01, D1-D3,
D8) is amplified at the buffer-amplifiers (02, IC5), then
applied to the prescaler circuit (IC4). The prescaler circuit
divides the applied signal, and outputs it to the VHF
DDS
circuit (lC1) via the buffer-amplifier (04). The VHF DDS
circuit generates digital signals using the applied signal as a
clock frequency. The phase detector section in ICl com-
pares it's phase with the reference frequency which
is
generated at the reference oscillator (Xl). IC1 outputs
off-phase components
as pulse signals via pins 52, 53.
The output pulses are converted into DC voltage at the loop
filter circuit (IC2a) and then applied to the VHF VCO circuit.
The D/A converter (R15-R38), low-pass filter (L2-L4,
C4-C10) and buffer-amplifier (IC14) circuits are connected
to the
DDS output to convert the digital oscillated signals
into smooth analog signals.
The output DC voltage from the loop filter circuit is also
applied to the RF-A unit to control the tuned bandpass filter.
IC2b
>--- To RF-A board
01,01-03,08
I--_-_l,r-~ .. ~··~,'l-------A-l-L-O- To VHF 1st mixer circuit
T
\..:l} (RF-A board, 011, 012)
Xl: 30.2 MHz
L...-_--' ' •.....•....... _;
Prescaler I---C
1/8
IC4 IC5 VHF PLL circuit
r---------------------------
_________________________ ..J IC7b UHF PLL circuit
-:>--_ To RF·B board
IC6
IC7a
05,04,010
I----+---:--~I Phase
.--'--- __ 1detector 1-'---1
Loop
filter
1----4 __ i:r-~ .. ~ .. ~;:' ___ --..~B:....l~L:....O_ To UHF 1st mixer circuit
T \..:l} (RF-B board, 014, 015)
'------' '.............. _;
Prescaler I---C
1/8
08
IC9 09
014
B2LO T UHF d' ..
1----------- ________ 0 2n mixer CircUit
(RF-B board, 011)
>---------- To BFO circuits (MAIN unit, ICl 01, IC103)
024
4-6

4-3-2 UHF PLL CIRCUIT (PLL UNIT)
The UHF PLL circuit generates the 1st LO frequency, and
the signals are applied to the 1st mixer circuits
in the RF-B
unit. The PLL circuit consists of a VCO, prescaler and DDS
circuits.
The signal generated at the UHF VCO circuit (05,
D4, D10)
is amplified at the buffer-amplifiers (06, 09), then applied to
the prescaler circuit (IC9). The prescaler circuit divides the
applied signal, and outputs it to the UHF DDS circuit (IC6)
via the buffer-amplifier (08).
The pulses output from the UHF DDS circuit are converted
into
DC voltage at the loop filter circuit (IC7a) and then
applied to the UHF VCO circuit.
The output
DC voltage from the loop filter circuit is also
applied to the RF-B unit to control the tuned bandpass filter.
4-4 POWER SUPPLY CIRCUITS
4-4-1 VOLTAGE LINES
Line Description
HVF The voltage from the external power supply
passed through the internal fuse (PA-B unit, F1).
The same voltage as the HVF line (external
13.8 V power supply) which
is controlled by the
[POWER) switch.
Common 9 V converted from the 13.8 V line by
9V
the 9 V regulator circuit (MAIN unit, IC25). The
output voltage is applied to the PLL,
demodulator and
+5 regulator circuits, etc.
Common 5 V converted from the 13.8 V line by
5V
the 5 V regulator circuit (PLL unit, IC11). The
output voltage
is used in the PLL unit only.
Common - 5 V converted from the 13.8 V line
-5V
by the - 5 V DC-DC convertor circuit (MAIN
unit, IC26). The output voltage is applied to the
AGC, APC and ALC circuits, etc.
Common 5 V converted from the 9 V line by the
M+5 5 V regulator circuit (MAIN unit, IC27). The
output voltage is applied to the BFO circuits and
optional units, etc.
Common 5 V converted from the 13.8 V line by
F+5 the F+5 regulator circuit (DISPLAY unit, IC13).
The output voltage is used in the DISPLAY and
SW-A units.
8 V for transmitter circuits which is converted
T8V
from the 9 V line by the T8 generator circuit
(MAIN unit, Q36, Q45).
8 V for receiver circuits which is converted from
R8V
the 9 V lin~ by the R8 generator circuit (MAIN
unit, Q37, Q41).
9 V for transmitter circuits, particularly the PA-A
PAT9 unit, which is converted from the 9 V line by the
PAT9 generator circuit (MAIN unit, Q42, Q45).
9 V for transmitter circuits, particularly the PA-B
PBT9 unit, which
is converted from the 9 V line by the
PBT9 generator circuit (MAIN unit, Q43, Q44).
4-7
4-5 PORT ALLOCATIONS
4-5-1 CPU (DISPLAY UNIT, IC1)
Pin Port Description
number name
9 RES Input port for reset signal.
Outputs control signal for speech
15 LCOMP compressor circuit.
"High": Compressor ON
19 SCK1 Output port for serial clock signal.
21
S01 Output port for serial data.
22 SCK2 Output port for serial clock signal for
PLL circuits.
23 STPA Output port for strobe signals for VHF
DDS circuit (PLL unit, IC1).
24
S02
"Output port for serial data for PLL
circuits.
25 STPB Output port for strobe signals for UHF
DDS circuit (PLL unit, IC6).
Input port for unlock signal from UHF
32 LCTB PLL circuit.
"High": When PLL-B is unlocked.
Input port for unlock signal from VHF
33 LCTA PLL circuit.
"High": When PLL-A is unlocked
Input port for optional speech
37 VBUSY synthesizer busy signal.
"High": During speech
40-43
KR1-
Input ports for key matrix.
KR4
44-51
KS1-
Outputs strobe signals for key matrix.
KS8 Outputs AF mute signal to the squelch
52 AFMM control gate (MAIN unit, IC16b/d) for
MAIN band.
Outputs AF mute signal to the squelch
53 AFMS control gate (MAIN unit, IC25b/c/d) for
SUB band.
54 MT8A Outputs control signal for
VH F
transmitter circuits
in RF-A unit.
Outputs control signal for VH F
MR8A receiver circuits
in RF-A unit while
55 VHF signals are being received
on the
MAIN band.
Outputs control signal for VHF
SR8A receiver circuits
in RF-A unit while
56 VHF signals are being received
on the
SUB band.
57 MT8B Outputs control signal for UHF
transmitter circuits
in RF-B unit.
Outputs control signal for UHF
MR8B receiver circuits
in RF-B unit while
58 UHF signals are being received
on the
MAIN band.
Outputs control signal for UHF
SR8B receiver circuits
in RF-B unit while
59 UHF signals are being received on the
SUB band.
78 BEEP Outputs beep audio signals.

CPU (DISPLAY UNIT, IC1; continue)
MAIN unit, IC10
Pin
Port
number
name
Description
Pin Port
number name
Description
79 EKEY Output port for electronic keyer signal.
81
MET Outputs meter signals with a
PWM
wave form.
82,83
DIUP, Input ports for the main dial using
pulse signals.
4 NB Outputs noise blanker control signal.
"High": Noise blanker activates.
5 SATL Outputs control signal for satellite
mode.
EDOT, Input ports for electronic keyer,
84,85
EDSH "EDOT" for dot and "EDSH" for dash
signal.
Outputs audio select signal.
6 MSC "High": MAIN band's audio signals
are selected.
90 ADSSM Input port for SUB band's S-meter
signal.
11 SDOFF Outputs PTT disable signal to ignore
SEND input from the ACC connector.
91 ADSCM Input port for SUB band's center
indicator signal.
92 ADSMS Input port for MAIN band's S-meter
signal.
93 ADMCM Input port for MAIN band's center
indicator signal.
94 ADSNO Input port for SUB band's noise level
signals.
Outputs UHFtransmitter circuit control
12 BT8 signal.
"High": Transmitting on UHF.
Outputs both VHF and UHF receiver
13 R8
circuit control signals.
"High": Receiving on VHF/UHF.
Outputs VHF transmitter circuit control
95 ADMNO Input port for MAIN band's noise level
signals. 14 AT8 signal.
"High": Transmitting
on VHF.
96 ADRF Input port for Tx RF level signal.
97 ADALC Input port for ALC level signal.
98 ADPTT Input port for [PTT) switch.
99 ADMIC Input port for up/down signal from the
microphone. MAIN
unit, IC24
Pin Port
number name
Description
~54 OUTPUTEXPANDERICs
4 SCWN Outputs CW-N mode select signal for
SUB band.
MAIN unit, Ica
5 SCW Outputs CW mode select signal for
SUB band.
Pin
Port
number name
Description
6 SSSB Outputs SSB mode select signal for
SUB band.
4 MCWN Outputs CW-N mode select signal for
MAIN band.
Outputs AGC time constant control
7 SAGC signal for SUB band.
"High": AGC fast is selected.
5 MCW Outputs CW mode select signal for
MAIN band.
11 SSCN Outputs scan signal for SUB band.
6 MSSB Outputs SSB mode select signal for
MAIN band. 12 TSFM Outputs switching signal of tone
squelch filter for SUB band.
Outputs AGC time constant select
7 MAGC signal for MAIN band. 13 /SFM Outputs
FM mode select signal for
SUB band.
"High": AGC fast is selected.
11 MSCN Outputs scan signal for MAIN band. 14 SFM Outputs non-FM mode select signal
for SUB band.
12 TSFM Outputs switching signal of the tone
squelch filter for MAIN band.
13 /MFM Outputs non-FM mode select signal
for MAIN band.
14 MFM Outputs
FM mode select signal for
MAIN band.
4-8

MAIN unit, IC108
Pin Port Description
number name
4 SIDE Outputs side-tone select signal.
5 PHOUT Outputs switching signal for head
phone audio select.
Outputs high speed packet control
6 EXMOD signal.
"High": 9600 bps is selected.
11
BKIN Outputs break-in control signal.
12
TOTe
Outputs TOT control signal.
Outputs microphone amplifier gain
13 EGAIN switching signal for external audio
input.
DISPLAY unit, IC8
Pin Port Description
number name
Outputs attenuator control signal for
ATT140 VHF band.
4 "High": When attenuator is
activated.
Outputs attenuator control signal for
ATT400 UHF band.
5 "High": When attenuator is
activated.
Outputs pre-amplifier control signal for
PRE140 VHF band.
6 "High": When pre-amplifier is
activated.
Outputs pre-amplifier control signal for
PRE400 UHF band.
7 "High": When pre-amplifier
is
activated.
12 LDIM Outputs dimmer control signal.
"High": Bright
Outputs TX indicator control signal for
13 LEDTS SUB band.
"High": SUB TX indicator lights
Outputs TX indicator control signal for
14 LEDTM MAIN band.
"High": MAIN TX indicator lights
4-9

SECTION 5 ADJUSTMENT PROCEDURES
5-1 PREPARATION BEFORE SERVICING
• REQUIRED TEST EQUIPMENT
EQUIPMENT GRADE AND RANGE
DC power supply Output voltage : 13.8 V
DC
Current capacity : 25 A or more
RF power meter Measuring range :
1-60 W
(terminated type) Frequency range : 120-460 MHz
Impedance : 50Q
SWR : Less than 1.2 : 1
Frequency Frequency range : 0.1-460 MHz
counter Frequency accuracy: ±1 ppm or better
Sensitivity : 100 mV or better
FM deviation Frequency range : 120-460 MHz
meter Measuring range : 0 to
+5 kHz
Audio generator Frequency range : 300-3000 Hz
Output level :
1-500 mV
Spectrum Frequency range : At least 1300 MHz
analyzer Spectrum bandwidth: ±100 MHz or wider
Attenuator Power attenuation : 50 or 60 dB
Capacity : 60 W or more
• CONNECTIONS
FM deviation
meter
Speaker
Attenuator
50 or 60 dB
AC to [EXT SP]
millivoltmeter
CW keyer to [KEY]
DC power supply to [DC 13.8 V]
13.8 V / 25 A
• Microphone connector
Audio
generator
Pin 1 Pin 7
MI, INPCj)Cp:f::
Pin 5
PTT
EQUIPMENT
Sweep generator
Standard signal
generator (SSG)
Digital multimeter
DC voltmeter
Oscilloscope
AC millivoltmeter
Ammeter
RF voltmeter
External speaker
to [ANT]
GRADE AND RANGE
Frequency range :
120-460 MHz
Sweep bandwidth : At least 50 MHz
Output impedance
:50Q
Frequency range :
120-460 MHz
Output level :
0.1 I1V-32 mV
(-127 to -17 dBm)
Input impedance :
10M Q/DC or better
Input impedance : 50
kQN DC or better
Frequency range :
DC-20 MHz
Measuring range : 0.01-10 V
Measuring range : 10 mV 10 V
Measuring capacity : 25 A
Frequency range
Measuring range
Impedance
Max. input power
Attenuator
50 or 60 dB
: 0.1-460 MHz
: 0.01-10 V
:8Q
:5W
Spectrum
analyzer
_------l RF power meter
60 W /50Q
VHF
_----I Standard signal
generator
UHF
CAUTION:
DO NOT transmit while
a SSG
is connected.
CAUTION:
When the [PREAMP] switch is
turned
ON, DC voltages are
applied to the antenna connector.
This may damage the signal
genarator.
rTERMiNATOR-for ~et~r~~uel~h-l
, and meter reference adjustment. i
t:J II POl
2-conductor 3.5 (d) mm (1/8") !
~~~~~~~ ~nd ~ute~ PIU~':' ___ J
5 -1

5-2 PLL ADJUSTMENT
MEASUREMENT ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONS VALUE POINT
UNIT LOCATION UNIT ADJUST
REFERENCE 1 • MAIN band Ireq. : Any PLL Connect
an RF Maximum level PLL L42, L43
FREQUENCY • Preset
C1 07 to the center position. voltmeter
(50 Q (More than
• Receiving impedance) to J3 pin
1.
-22 dBm)
2 • MAIN band Ireq. : Any Connect a Irequency 60.40000 MHz The trimmer
• Receiving counter to J3 pin
1. capacitor 01
X1
VHF LOCK 1 • MAIN band Ireq. : 145.000 MHz PLL Connect a digital
3.0V PLL L7
VOLTAGE • Mode
:FM multimeterto W11.
• Receiving
2 • MAIN band Ireq. : 136.000 MHz 2.2 V
±0.5 V Verify
3 • MAIN band Ireq. : 174.000 MHz 6.2 V ±0.5 V
4 • MAIN band Ireq. : 145.000 MHz Connect
an RF -10dBm±3dB
• Receiving voltmeter (50 Q
impedance) to W11.
UHF LOCK 1 • MAIN band Ireq. : 440.000 MHz PLL Connect a digital
4.0V PLL C107
VOLTAGE • Mode
:FM multimeter to W13.
• Receiving
2 • MAIN band Ireq. : 420.000 MHz 1.6 V
±0.5 V Verily
3 • MAIN band Ireq. : 460.000 MHz 6.5 V
±0.5 V
4 • MAIN band Ireq. : 440.000 MHz Connect an RF
-9 dBm ±3 dB
• Receiving voltmeter (50 Q
impedance) to W13.
5-3 FREQUENCY ADJUSTMENT
MEASUREMENT , ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONS VALUE POINT
UNIT LOCATION UNIT ADJUST
FM TX-LO 1 • MAIN band Ireq. : Any MAIN Connect a Irequency 10.85000 MHz MAIN L18
FREQUENCY • Mode
:FM counter to J27.
• Transmitting
5-2

-PLL UNIT
Reference
frequency J3 Pin1
check point
-MAIN UNIT
FM TX-LO
frequency
check point J27
L43 ] Reference
frequency
L42 adjustment
X1 Reference
frequency
adjustment
C107 UHF lock
voltage adjustment
L7 VHF lock
voltage adjustment
W11 VHF lock
voltage
check point
L18 FM TX-LO
frequency
adjustment

5-4 RECEIVER ADJUSTMENT
MEASUREMENT ADJUSTMENT
ADJUSTMENT ADJUSTMENT CONDITIONS VALUE POINT
UNIT LOCATION UNIT ADJUST
VHF 1 • MAIN band Ireq. : 144.000 MHz MAIN Connect a DC Maximum level RF-A Adjust in
SENSITIVITY • Mode
:FM
voltmeter to C.P. (M-S). sequence
(MAIN BAND) • Connect
an SSG to the [VHF ANT] L16, L15,
connector and set as: L14, L13,
Level :
3.2IlV* (- 97 dBm)
L21
Modulation : 1 kHz
Deviation :
±5 kHz
MAIN L 11, L12,
• Receiving L13
2 • Mode :USB Rear Connect an AC Maximum audio MAIN Adjust in
• Set an SSG as: panel millivoltmeterto the output sequence
Level
:O.lIl
V
*( 127 dBm) [MAIN SP) jack with an L25, L27,
Modulation : OFF
8Qload.
L28
VHF 1 • SUB band Ireq. : 144.000 MHz MAIN Connect a DC Maximum level MAIN Adjust in
SENSITIVITY • Mode
:FM voltmeterto C.P. (S-S). sequence
(SUB BAND) • Connect
an SSG to the [VHF ANT] L46. L47,
connector and set as: L48
Level :
3.2IlV· (-97 dBm)
Modulation : 1 kHz
Deviation :
±5 kHz
2 • Mode : USB Rear Connect an AC Maximum audio Adjustm in
• Set an SSG as: panel millivoltmeterto the output sequence
Level
:0.1Il V *(-127dBm} [SUB SP) jackwith an L38. L40,
Modulation : OFF
8Qload. L41
VHF 1 • MAIN band Ireq. : 144.00000 MHz Rear Connect an AC 1.5 kHz audio SSG Output
TOTAL GAIN • Mode
:USB
panel millivoltmeterto the frequency
(MAIN BAND) • Connect
an SSG to the [VHF ANT] [MAIN SP) jackwith an
connector and set
as: 8 Qload.
Level : 1
mV' (-47 dBm)
Modulation : OFF 1.0 V
(0 dB) Front [MAINAF)
• Receiving panel control
2 • Set
an SSG level as: OFF 100
mV(-20 dB) MAIN R239
VHF 1 • SUB band Ireq. : 144.00000 MHz Rear Connect an AC 1.5 kHz audio SSG Output
TOTAL GAIN • Mode
:USB
panel millivoltmeterto the frequency
(SUB BAND) • Connect
an SSG to the [VHF ANT] [SUB SP) jackwith an
connector and set
as: 8 Qload.
Level : 1 mV*
(-47 dBm)
Modulation : OFF 1.0 V
(0 dB) Front
[SUBAF]
• Receiving panel control
2 • Set
an SSG level as: OFF 100
mV (-20 dB) MAIN R378
'This output level 01 the standard signal generator (SSG) is indicated as SSG's open circuit.
5-4