Kenwood R-280 User manual

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KENWOOD
v:;;-1" .'^:'£ ^VB^^ flRHnMI
R-820
HIGH PERFORMANCE HF AMATEURBANDRECEIVER

CONTENTS
R.820
SPECIFICATIONS ...................... ................................................3
FEATURES .................................................................................4
BLOCK DIAGRAM .....................................................................5
GENERAL ............................................................................. , .....6
CIRCUITDESCRIPTION ............................................................7
FUNCTIONALDESCRIPTION ....................................................9
MODIFICATION OFTHE TS-820 ..............................................11
PANEL CONTROLS ....................................................................13
PARTS ALIGNMENT/PACKING ................................................14
PARTS LIST ...............................................................................31
EXPLODED VIEW ....44
•
DISASSEMBLY ........................................................ . .................45
TROUBLESHOOTING .................................................................47
LEVEL DIAGRAM ......................................................................50
ADJUSTMENT ...........................................................................51
OPTION ......................................................................................58
SCHEMATICDIAGRAM ............................................................59
CONNECTOR ALIGNMENT.. ..60

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SPECIFICATIONS
FrequencyRange
1 60 meterband
80 meterband
40 meterband
20 meterband
1 5 meterband
10 meterband A
10 meterband B
10 meterband C
10 meterband D
1 1 9 meterband (WWV1/JJY
Shortwave band:
49 meterband
31 mei<;r band
25 metir band
1 6 meter band
1.8 ~
3.5 ~
7.0 ~
14.0 ~
21.0 ~
28.0 ~
28.5 ~
29.0 ~
29.5 ~
15.0 ~
5.9 ~
9.4 ~
11.5 ~
17.7 ~
2.0MHz
4.0MHz
7.5 MHz
14.5 MHz
21.5 MHz
28.5 MHz
29.0 MHz
29.5 MHz
30.0 MHz
15.5 MHz
6.4MHz
9.9MHz
12.0 MHz
18.2 MHz
Notch Filter Attenuation
Morethan 50dB
Frequency Stability
Within 1 00 Hz during any30 minuteperiodafterwarm up
within ± 1 kHz during the first hour after 1 minute of
warm up.
Antenna Impedance
50 ~ 75J) (unbalanced)
AF Output
Morethan1.5W (8fi load, 10% distortion)
AF LoadImpedance
4 ~ 16Q for both speaker and headphone
Mode
SSB, CW,AM, RTTY
Receiver Sensitivity
SSB 0.25 juV (SW Band 0.5 pV) S + N/N 10 dBor more
AM 1.5 jiV (SW Band 3 0V) S + N/N10dBor more
ImageRatio
Better ihan 80dB(SW Band better than 50dB)
IF Rejection
IF Frequency is90dBor moredownfrom output signal
(SW Bandmorethan 40dB)
Receiver Selectivity
CW(025) morethan 250Hz(-6 dB),less than 500Hz
(-6dB) (*,)
CW (0.5)morethan 500Hz(—6 dB),lessthan 850Hz
(-60 dB) (*2)
SSB (2.4)morethan 2.4kHz (-6 dB),lessthan 3.9kHz
(-60 dB)
AM(6) morethan 6 kHz( — 6dB). less than 12 kHz (—60
dB)
Variable Bandwidth
CW (05) 150 Hz-
SSB (2.4) 600Hz
AM (6)4.3kHz~
< 500Hz(-6dB) fullyvariable (*3)
~ 2.4kHz(-6dB) fullyvariable
6 kHz(-6dB) fullyvariable (M
Installedoptionalfilter-YG-455CN
*2 Installedoptionalfilter-YG-455C
*3 Installedoptionalfilter-YG-88C and YG-455C
*4 Installedoptional filter-YG-88A
Power Consumption
AC 120V, 30W
DC 13.8V,1.6A
PowerSupply
AC 100, 120, 220,240V, 50/60 Hz
DC 1 2 ~ 1 5V
Semiconductors and Tubas
IC's
FET's
Transistors
Diodes
Tube
40
34
89
170
1
Dimensions
13-1/8" (W)x6" (H)x 13-3/16"
(Protection not included)
(D)
NOTE:
The circuit and ratings may change without notice dueto
development in technology.

FEATURES
1
High Performance HF Amateur Band Receiver
The R-820 is KENWOOD'S high performance
communication receiver,designed to meetdiversified
demands in variousoperationmodes intheHF band.
A highlyrefinedversion ofthe TS-820's receiversection,
the R-820 covers allHF amateurbands(1.8 MHz~
297 MM/) plus WWVand selected SW Bands, and
operator; in theCW, SSB, andAM modes.
2. FullTransceiverCapability
In combination with a TS-820 seriestranceiver, the
R-820 can provide split frequencyoperation.Shared
MET andVFO frequenciesprovide"fulltransceive"
operation withidenticaltransmitting and receiving
frequency, as well as "VFO transceive" operation.
3. VariableBandwidth Tuning (VBT)
IF bandwidth is continuouslyfrontpaneladjustable,
making optimum IF bandwidth available forany
operating condition.Thisfeature is completely
independent oftheIF Shift.
4.50kHz Notch Filter
The notchcircuiteffectivelynullsnearbyinterfering
signals The R-820employs a fixednotchfilter. The
BFO and local oscillator are simultaneously varied soas
to obtainequivalentchanges inthe notchfrequency.
5. Double Tuned RF Circuits for Improved Cross
Modulation (2-Signal) Characteristics
Improvedfront end circuitelements and optimizedlevel
distribution have greatlyenhanced intersignal perform-
ancessuch as intermodulation and overload
characteristics. The introduction of double-tuned RF cir-
cuits providesincreasedselectivity and sensitivity.
6. IF Shift to Cope with all Receiving Conditions
The IF Shiftcircuit, oneofthe highlyevaluatedfeatures
used m the TS-820transceiver, has alsobeen
incorporated inthe R-820, providing remarkable
interference rejectionperformance,frequencyresponse,
and CW pitchcontrol.
7. Digital DisplayProvidesAccurateFrequency
Indication
The Digital frequencyreadoutprovidesprecise
indication tothe100Hz order, any band, any mode,
including the shortwavebands.
8. Superior Tuning Operation
The combination of analog and digitalreadoutsprovides
maximum nonvfinipnr^ nnd flevibility during operation.
9. Four Shortwave Bands with anAM Filter
The R-820 alsocovers the popular HF broadcast bands
of 49m, 31m,25m, and 16m. Itis supplied with a
built-in 455kHzAM filter; an 8.83 MHzAM filter
(YG-88A) is available as an/option.
10. Transmitter Signal Monitor
Transmitter output canbe monitored with the R-820 for
checkingfinalsoundquality.Monitorlevel is frontpanel
adjustable.
11. Optional IF Filters
Filters optionallyavailableare: 8.83 MHzCW filter
YG-88C, AM filterYG-88A, and455kHzCW filter
YG-455C (passband: 500Hz)and YG-455CN(pass
band: 250 Hz).
12. Additional Filter Switching
Additional filters are appropriately selected bythe
MODEswitch.Filterpassbands of 0.25kHz, 0.5 kHz.
2.4 kHz, and6 kHzcanbe selected by means ofthe
FilterSwitch.
13. Adjustable NoiseBlankerLevel and Audio
FrequencyResponse
The balanced-gatenoiseblanker circuit is provided with
a front panel noise threshold adjustment. This is
especially useful when noiselevels are relativelylow. A
frontpaneltonecontrol for audioresponseshaping is
also provided.
14. 10 dB-Stepped RF Attenuator (0~ 40dB)
The 1 0 dB steppedattenuatorprovides upto40 dB's RF
attenuation making it possible to receive strong local
signals orlow bandstationsoperating at night.
m
15. S-Meter with dB/VV Scale
The S-meter is provided with a dB/^V scale which can
be used for fieldintensitymeasurements in combination
with theRF step attenuator.
16. FullAccessory and Connecting Features
The R-820receiver is complete with fullaccessory and
connecting features such as:25kHz marker, display
holdswitch,transceive/separateselector,standby
switch, FIXEDchanneloscillators,NOTCH.FIX,VFO,
and RIT indicators, PHONEPATCH OUT jack, terminals
for IF output a observation (50 kHz) andpan display
connection(8.83MHz), anda recordingjack.

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BLOCK DIAGRAM
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GENERAL
The R-820receiver is tripleconversionsuperheterodyne for
the amateur bands, and quadruple conversion
superheterodyne through an additional29.5 MHz
intermediatefrequency forthe shortwavebands.
Fullamateurbandcoverageconsist of 1.8,3.5,7.0,14.0,
21.0.28.0,28.5,29.0, and 29.5 MHz bandsalong with 15
MHzWWV (JJY). Shortwavecoverageconsists ofthe49m
(5.9 ~ 6.4 MHz), 31m (9.4 ~ 9.9 MHz), 25m (11.5 ~
12.0MHz), and16m (17.7 ~ 18.2MHz)Bands.
Reception ofCW, SSB, RTTY, andAMareall possible.
The 1st,2nd, and3rd intermediate frequencies are 8830
kHz, 455 kHz, and50 kHz. The 1st IF stageusescrystal
filters with pass bandwidths of2.7kHz (SSB; supplied), 6
kHz (AM;optional), and0.5kHz (CW;optional). The2ndIF
stageusesceramic filters of6 kHz (AM; supplied) and2.7
kHz (SSB:supplied), and optionalcrystalfilters of0.5kHz
(CW) and 0.25 kHz (CW).
For enhancedselectivity, the R-820features
continuously-variable IF bandwidth,achieved by combining
the 1st and2ndIF filterresponses, andtheIF Shiftfeature.
A T notchfilter is incorporated inthe3rdIF stage.Amateur
frequencies canbe read by both the dial and Digital
frequency readouts.Shortwavefrequency is read bythe
Digital display only. Performance is assured inthe1stand
2nd mixers andthe converter by employingdual-gate MOS
FETs. (Refer to Figure 1.)
RF circuits are alsototaly of dual-gate MOSFET
configuration for increasedselectivity,signal-to-noiseratio,
andAGC performance.
The R-820receiver is capable of operating with the TS-820
transmitter asa completetransceiver.
Fig. 1 SSB Filter Variable Bandwidth
Characteristic
Fig. 2.T Notch Filter Attenuation
Characteristic
I
*

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CIRCUIT DESCRIPTION
i
*Coil Pack Unit (X44-1230-00)
The Coil Pack Unit isthe samebasicdesign as thatused in
the TS-820transceiver,excepting theRF section, which is.
double-tuned for higherselectivity.
*RF Unit (XX-1240-00)
The RF Unit consists ofanRF amplifier, 1st mixer, and
block bias circuits, and assembles tothe Coil Pack Unit.
*IF A Unit (X48-1190-00)
The IFA Unit consists ofan8 polecrystalfilter for 8830
kHz, filter and gatecircuits forthe noiseblanker, 2nd mixer,
ceramic and crystalfilters forthe2ndIFat455 kHz, 3rd
mixer, S-meter amplifier, and filterpresetswitches.
The standard suppliesfilters prea YG-88SW (8830 kHz)
and CFJ455K3 (455kHz) both for SSB, and CFR455H for
AM. Optional filters arethe YG-88A(AM) and YG-88C
(CW) both forthe 1st IF,and YG-455C(CW) and
YG-455CN (CW)both forthe2ndIF.
*IF B Unit (X48-1200-00)
TheIFB Unitcontains 3rdIF(50 kHz)circuits,consisting of
the notch filter, notch filterswitchcircuit,productdetector,
AM detector, switching AM detector switching circuit, and
AGC amplifier.
*NB Unit (X45-1330-00)
The NB Unit consists ofa noiseamplifier for noiseblanking.
*AFAVR Unit (X49-1080-01)
The R-820's AFAVR Unit is identical to that ofthe TS-820
transceiver, and includes the audiopoweramplifier, 9V
regulated powersupply, FET biassupply, and RIT adjust
circuits.
*PLL Ass'y Unit (X60-1010-01)
ThePLL Ass'y Unit consists ofthePD (Phase Detector) Unit
(X50-1 340-01) andtheVCO (VoltageControlledOscillator)
Unit (X50-1 330-00).
The R-820 hasa frontpanel switch for turning theHET
oscillator onand off; for transceiveroperation, HET output
accepted from the TS-820forms thePLL loop.
The PD Unit has separatecrystals for eachband, two
mixers, waveform shaping, and phase comparator. It
generates control forthe VCO,based onBFO output. It
also provides a pure electronic IF Shiftloop by using the
incomingcarriersignal.
The VCO Unit contains the voltagecontrolledoscillators for
each band,buffer amplifier, and oscillator output shut-off
circuit for loopunlock.Oscillationfrequencies are
controlled by voltagefrom thePD Unit. Band switching for
bothunits isby electronic(diode)switches.
*CAR Ass'y Unit (X60-1040-OO)
The CAR Ass'y Unitconsists ofIF Shift and VBT control
circuits, anda local forthe2nd mixer.
The CAR-1 Unit (X50-1480-00) hasan oscillator forIF
Shift, crystals for 8831.5 kHz (USB) and 8828.5 kHz (LSB).
switch circuit, andVXO circuit. It alsocontains an oscillator
frequency shiftcircuit forAM reception.
The CAR-2 Unit (X50-1460-00) consists of oscillators for
the 2nd mixer and VBT, which is equipped with an 8375
kHz (NORM)crystal andVXO circuit.
* Local OSC Unit (X50-1440-00)
The Local OSC UnitacceptssignalsfromCAR-1 and2 to
produce a 455kHz mixed output, and also produces a 505
kHz signal by mixing the455kHz mixed output with the50
kHz NOTCHsignalgenerated byitsown oscillator. It also
has 50kHz signalgenerator. The50kHz signal is used as
a BFO signal forthe productdetector, andthe505kHz
signal is used asa localsignal forthe3rd mixer.
*FIX Unit (X50-1450-00)
The FIX Unit consists ofan oscillator forthe4 fixed
channels, anda —6V power supply for blockbias.
* Indicator Unit (X54-1180-00)
This unitprovides "VFO", "FIX","RIT", and "NOTCH"
indication. TheVFOandFIX indicators also functionduring
transceiver operation with the TS-820.
*VR ASS'y (X54-1340-00)
TheVR Ass'y has variable resistors for monitor levelcontrol,
NB level control, and tonecontrol.
* Switch Ass'y (X41-1130-00)
Duringfulltransceiveoperation, the TRCV
activates theVFOandHET switchingcircuits.position
* RelayAss'y (X43-1190-01)
The Relay Ass'yconsists ofa standbyrelay, low voltage DC
p.owersupplycapacitors, andthe 5-volt stabilizedpower
supply forthePLL circuit. The standby relay switches block
biases andVFO power during transceiveoperation.
*VFO Ass'y (X40-1110-00)
The receiver'soverallfrequencystabilitydepends on that of
the VFO,since thePLL circuit is controlled byVFO output.
VFO frequency is5.0MHzto5.5 MHz.
*5V-AVR Ass'y (X43-1220-00)
The 5V-AVR Ass'ysuppliesregulated 5VDCtothe Counter
ass'y.
* Marker Ass'y (X52-0005-01)
The 100kHz synchronizes output from 01 is waveform
shaped by diode D1,Q2andQ3 multivibrator. The25kHz
multivibrator output is amplified by 04 andfedtothe
receiver input.
* Counter Ass'y (X60-1020-00)
The CounterAss'yconsists ofthe CounterMixerunit
(X54-1150-00) andthe Counter unit (X54-1160-00), both

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CIRCUIT DESCRIPTION
contained in a rigidshieldedcase. The countermixer
synthesized operatingfrequency by mixing thePLLand
carrieroutputs;Counter unit output drives the external
6-digit fluorescentdisplaytube.
* Converter Ass'y (X44-1250-00)
Shortwave broadcasts are crystalconverted tothe 29.5
MHz intermediatefrequency.Diodeswitching is employed
for converterselection.
The Converter Ass'y also hasa frequencyconverter forthe
Digital display,controlcircuits for HET/VFOswitching,
monitoring,frequencydisplayerasure, andthelow voltage
rectifier circuit.
* Frequency Configuration for Triple Conversion
The 1 st, 2nd, and3rd intermediatefrequencies forthe triple
conversion system are 8830 kHz. 455 kHz, and50 kHz.
Unlike conventionalreceivers, the R-820uses
high-selertivity IF filters for eachstage after the 1st mixer.
Crystal converters are used for each ofthe shortwave
bands.
Table 2
Table 1
Mode
LSB
USB
CW
RTTY
AM
Freq. kHz
8828.5
8831.5
8831.5
8828.5
8830.0
Band
WWV/JJY
1.8
3.5
7
14
21
28
28.5
29
29.5
HETMHz
205
7.3 ,
9.0
12.5
19.5
26.5
33.5
34.0
34.5
35.0
VCO
23.83 -
10.63 -
12.33 <•
15.83 -
22.83 -
29.83 -
36.83-
- 37.33 -
37.83 '
38.33 -
MHz
- 24.33
- 11.13
- 12.85
- 16.33
- 23.33
~ 30.33
- 37.33
~ 37.83
- 38.33
-38.83
Table 3
Band
49m
39
25
16
ReceivingFreq.
MHz
59~6.4
94~9.9
1 1 5~12.0
17.7~18.2
OSCMHz
23.6
20.1
18.0
11.8
VCO MHz
38.33~38.83
38.33~38.83
38.33~3883
3833~38.83
CVO MHz
14.73~15.23
18.23~18.75
20.33~20.83
26.53~27.03
FILTERFILTERNOTCH
T
3.33<v3.83MHz
USB 8.8315MHz 2=, \ /
== s '
LSB 8.8285MHz
V'
USB 48.5KHz
LSB 51.5KHz
Fig. 3 Frequency Configuration

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FUNCTIONALDESCRIPTION
29.5-v 30.0MHz
COUNT
MIX.T CVO
Fig. 4 Shortwave BandConverter
*VBT andIF Shift Features
The VBT (Variable Bandwidth Tuning) continuously varies
theIF filter pass band. The variablerange for each IF filter
is shown in Table 4.
Table 4
When a 1 4.0MHzUSB signal is received in theSSB mode,
the VFO, CAR-1, and MET generate 5.5 MHz, 8.8315 MHz,
and 19.5 MHz signals.Oscillationinjection tothe1st
mixer is 22.8315 MHz.Therefore, theSSB signal of
14.0015 MHzis converted bythe 1st mixer into 8.830
MHz.Thissignal is furtherconverted to455kHzbythe
2nd mixer andto50kHzbythe3rd mixer. At this stage,
variable bandwidth is controled by adjusting CAR-2
frequency VBT control. For simplifiedexplanation,assume
filters F2andF5 passbandsnormalCAR-1 and CAR-2
conditions are2.7 kHz.
[Example-1 ]
Bandwidth 1.7kHz
IF shift 0 kHz
Under the aboveconditions, the input frequency of 14.0
MHz provides:
CAR-2 8374.0 kHz (VBTcontrol)
CAR-1 ?.. 8831.0 kHz(IF shiftcontrol)
NOTE:
One half ofthe frequencyvariationprovided bythe VBT.
CenterFreq Bandwidth
Bandwidth ( —r,dB)
F2(kHz)
8830
8828 65-8831 35
F5(kHz)
455
453.65~45635
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1st
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CAR-1 8.8315MHz
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CAR-2 8.375KHz
1
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1
1
1
1
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1
1
1
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1
1
1
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8.8295MHz
-£ -1
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0
1
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1
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1
1
1 C
8.374MHz
©
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1
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1
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1
1
-2 012
8.8315MHz
®
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1
1
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1
1
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-e - r 6 i e
8.374MHz
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484950 51 52
KHz
®
toto ee> s< es
KHz
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Fig. 5 Description of VBT-IF Shift

FUNCTIONAL DESCRIPTION
Circuit is obtained through, CAR-1 manipulation. The14
MHzUSB signalactuallycovers a frequency of 14.0015
MHz± 1.35MHz. CAR-1 8829.5 kHz,provides forVCOat
22.8310 MHz.
Therefore, the 1st IF signalshifts by500Hzto become
8829.5 kHz ±1.5 kHz. As previously mentioned the1 stIF
filter passband width is 8.830 MHz± 1.35 kHz.Thismeans
that the frequency component is reduced by500Hzas
compared with the standardcondition as illustrated in Figure
5-3. The1 stIF signal is then converted tothe2ndIFat455
kHz ± 1.35 kHzas shown in Figure5-4, and finallybecomes
455.5 kHz± 850Hz with a bandwidth of1.7 kHz.This is
equivalent toan antenna input frequency of 14.001 5 MHz±
850Hz. Thisalsoshows theIF Shiftfunction isnot
activated.
[Example-2]
Bandwidth 1.7kHz
IF Shift +500'Hz
Undertheseconditions, an incoming USB signalprovides:
CAR-2 8374.0 kHz (VBTcontrol)
CAR-1 8831.5 kHz(IF Shift control)
From example-1, letus determine in reverse the incoming
signalfrequencydistribution by tracing up from the2ndIF.
It is knownfromexample-1 that the2ndIF centerfrequency
is 455.5 kHz with its upper limit placed at 455.5 kHz+ 850
|Hz. This 2ndIFcanbe reverseconverted tothe 1st IFas
455.5 kHz+ 8374 kHz= 88295 kHz with its lower limit
placed at 8829.5 kHz— 850Hz. Therefore, the signal
componentspassing through the1 standthe2ndIF filter are
identical to those in example-1.However, the CAR-1
frequency of 8831.5 kHz for example-2, which is 8831.0 kHz
in example-1,gives a VCO output of 22.8315 MHz. The
88.29.5 kHz frequency component convertedfrom the1 stIF
can further be converted tothe incoming frequency of
14.002 MHz+ 850Hz. This is equivalent toa signal of 1.7
kHz bandwidth,shifted + 500Hz.
As knownfromexample-1 and2,theVBTandIF Shift
operateseparately, permitting totallyindependent control of
IF bandwidth and centerfrequencyshifting.
* NOTCH Circuit configuration
Despitefrequencyvariationsproduced bytheIF Shift, the
3rdIF centerfrequencyremainsconstant,fixed at50 kHz.
The3rdIF centerfrequency canbe varied by changing
CAR-3 frequency. At this time, the pitch between the3rdIF
andthe carrierfrequencyremainsunchanged. A fixed 50
kHz notchfilter is inserted into the3rdIF circuit to eliminate
interferingsignalsonly.
NOTCH FILTER
50KHz
-AF
48.5KHz
51.5KHz
Fig. 6 T Notch Filter
•Monitor Circuit
Duringtransceiver operation, turning the MONITORswitch
ON while transmittingturns 012, onthe Converter ass'y
ON. ThisturnsRL-2OFF,shutting off incomingsignals
from the receiverantenna.Meanwhile, the R-820's
antennaterminal is groundedthrough j resistor to
minimizesignal leakage. Also, the voltageapplied toG2of
Q1 through 04 ontheRF ass'y is controlled to adjust FET
gam. Thisreducesoverallgain by morethan 70dB.
OFF
RB
p
-6V
MONITOR LEVEL
VR2
RBC
Q3,4
Fig. 7 Monitor Circuit
*NB LEVEL CONTROL Circuit
The NB circuit forthe R-820receiver is quitesimilar to
conventionalcircuits. In Figure 8, noise signuls are voltage
doubled by diodes D1andD2.Q5 creates suppliesdriving
signal fortheNB switching gate.
Q5 emittervoltage is variable; thresh-old level canbe
controlled for weaksignals.
The maximum(clockwise) NB LEVEL controlposition
provides the maximum NB threshold level.
The range of emittervoltagevariation is approx.1.9V to
0.6V, and provides anNB levelvariationrange of approx.
10dB.
10

FUNCTIONAL DESCRIPTION/MODIFICATION OFTHE TS-820
To Switch Gate
Circuit
NB LEVEL
VR I 300(1(8)
Fig. 8 NB Level Control Circuit
*TONE Circuit
The Tone circuitshapesaudio output high frequency
response The maximum (clockwise) position ofthe TONE
control provides the flatestresponse, with maximum clarity.
Fig. 9 Tone Circuit
TS-820 TRANSCEIVER MODIFICATION
Thissectiondescribesmodification tothe TS-820 transceiver
for operating with the R-820receiver asa complete
transceiver:
Modifications tothe TS-820
1. Remove and insulate the coaxialcable from theIFOut
jack. Connect thePLL Ass'y PD Unit (X50-1 340-00)
TP-4 totheIFOut jack by using the supplied 75Q
1.5C-2V coaxialcable.Cablelayoutshould bein
accordance with Figure 1 1.
To IF- Out Pin Jock
I.5C-2V
Coax. Cable
TP-4
Fig. 10
2. Remove the lead from the common terminal onthe
stage and connect thetwored wires tothe common
terminal. Connect the MODE-SW's common terminal
for switching between theUSBandLSB crystals with
theEXTVFO socket pin®.
3. Remove and insulate the lead from theEXTVFO socket
pin®.
4. Connect 2 capacitors (0.01/iF) across pins(Dand (5)and
(Dand®on theEXTVFO socket.
5 Connect pins®with ®onthe 9P-MT EXTVFO plug.
6. Insulate and secure all cables and leadsremoved from
theiroriginal positions so they donot short.
Modification Procedure
1. Remove thePLL Ass'y from the transceiver by4 screws,
and disconnect all multiconnectors.
2. Remove thePD unit shield.
3. Remove thePD unit by5 screws.
11

FUNCTIONAL DESCRIPTION/MODIFICATION OFTHE TS-820
^
To the common
terminal onthe
FIX CH switch
"W.
I »!
"' "
1
"~v '-v
FIX CH knob
k
1.5C2V
coaxialcable
To the
IFOUT jack
. To EXT VFO
socket pin®
—ToEXTVFO
socket pin®
Mode knob
Fig. 11 Viewed from Bottom
4. Connect TP4onthePD unit with theIF Out jack by
using the supplied 75Q 1.5C-2Vcoaxialcable,(Fig. 11).
5. Onthe MODEswitch,reconnect thered lead tothe
terminal with the orangelead.Remove the jumper
across the terminals fortheredand orangeleads.
Connect the MODEswitchterminalfrom which the.red
lead was removed with pin (2) ontheEXTVFO socket.
(Fig.12).
6. Remove and insulate the leadfrom theEXTVFO socket
pin ®connect the common 9V terminal ontheFIXCH
switch with theEXTVFO socket pin®(Fig. 13).
7. Connect 2 capacitors (0.01/iF) across pmsCDand (5) and
®and® on the. EXTVFO socket.
8. Connectpins 4 and7 onthe 9P-MT VFO plug.
9. Whenconnecting a remoteVFO,such asthe VFO-820,
remove and insulate the leadfrom pin4 onone 9P-MT
plug, and connect pin® with pin® onthe
transceiver-side plug. Aftermodification, the Remote
VFO lamps won't light.*
ToEXTVFOPin7 ToEXTVFO socket
ANTI-VOX MODIFICATION
Thissectiondescribes the modificationprocedure to supply
Anti-VOX duringfullytransceiveroperation ofthe R-820
receiver and TS-820 transceiver.
Modification Procedure
1. Connect two 100J2 1/4Wresistors tothe terminalstrip
as in Fig. 14, and secure the terminalstrip bythe Digital
Unit mounting screw.
2. Remove the green wire from the Audio-AVR unit tothe
PHONE jack and reconnect ittothetwo1 OOQ resistors
common connection.Connect the PHONE jack to either
of the 10012 resistors.
3. Remove the green and white/red leadsfrom the PHONE
PATCH OUT terminal,connect them together and
insulate.
4. Connect the PHONEPATCH OUT tt-iminal tothe
remaining 100Q resistor.
To AF2 terminal
at AF-AVR unit
ToSP terminal
at VOXVR unit
Stopper
FIX-CH SW
Fig. 13
Fig. 14
12

•
D
PANEL CONTROLS
FRONT PANEL
Knob (FIX CH)
(K21-0279-04)
Front glass
(B10-0611-04)
Badge
(B43-0610-04(W,K)
(B43-0609-04IT)
Meter
(B31-0610-05)
Calibration knob
(K29-0629-04)
Paddle switch
(S44-2020-05)
Paddle switch
(S44-2016-05)
Paddle switch
(S44-2015-05)
US Jack
(E11-0003-05)
Panel back plate
(B03-0506-04)
Knob
(K23-0239-04)-
REAR PANEL
LED
(SEL103W)
Dial Scale (A)
(820-0374-03)
Dial Scale (B)
(B20-0375-04)
Knob
(K21-0269-04)
Knob
(K23-2040-04)
Dial escutcheon
(B01-0105-05)
Mainknob
Washer
(K21-0709-05)(N17-2030-46)
Lever knob
(K23-0709-04)
Case
(A01-0722-02)
Case screw
(N35-4006-41)
Knob
(K21-0267-04)
Bottom case
{A40-0602-OD
Knob (Notch)
(K23-0241-14)
Panel
(A20-2326-05)
Knob (RF Gain)
(K21-0268-04)
Panel screw
(N33-4008-45)
Power switch
(S59-2020-05)
US jack
(El 1-0003-05)
Modelnameplate
(B40-2433-04)
1 P pin jack
(E13-0101-05)
Earth screw
(N09-0256-05)
4P connector
(E08-0409-05)
Leg (Large)
(J02-0049-14)
Fuse holder
(J13-0403-05)
Batterfly nut
(N14-0020-04)
Rubber cap
(809-0011-04)
Slideswitch
(S31-2007-05)
M type receptacle
(E04-0102-05)
13

PARTS ALIGNMENT
VIEWEDFROM TOP
IF-A unit
(X48-1190-00)
Counter ass'y unit
(X60-1020-00)
VFO unit
(X40-1110-00)
Coil packunit
(X44-1230-00)
RFunit
(X44-1230-00)
5V-AVR unit
(X43-1220-00)
FIX unit
(X50-1450-00)
LO unit
(X50-1440-00)
IF-B unit
X48-1200-00)
VIEWEDFROM BOTTOM
PLL ass'y unit
(X60-1010-01)
AF AVR unit
(X49-1080-01)
Counter ass'yunit
(X60-1020-00)
Car ass'y unit
(X60-1040-00)
Conv. unit
1X44-1250-00)
Relay unit
(X43-1 190-01)
Marker unit
(X52-0005-01)
NBunit
(X54-1330-00)
14

PARTS ALIGNMENT/PACKING
VIEWED FROMCOMPONENTSIDE (IF-A Unit)
IF-A Unit (X48-1190-00)
PACKING
DescriptionQ'ty
Accessory bagA (H25-0029-04)
Fuse(F05-1023-05)
Phone plug (E12-0001-05)
Screw (N30-401 2-46)
1Ppinplug(E14-0101-05)
2
1
2
5
Accessory bagB (H25-0077-03)
White/red wire
Coax cable 1.5C-2V (slipped 75S2)
Ceramic (OOljiF)
1m
1m
2
Accessory bagC (H25-01 1 2-04)
Accessory bagA,B
Leg (Large) (J02-0049-14)
Counter calbe (E3 1 -0039-05)
Cable (MET) (E30-1616-05)
Cable (ANT)(E30-1617-05)
Cable (GNDME30-1619-05)
2
1
1
1
1
Cushion
(H10-1276-04)
Styrenfoam cushion R
(H10-1447-02)
styren foam cushion F
(HI 0-1446-02)
Cushion
(HI 0-1276-04)
Operatingmanual
B50-2572-00 (K.W)
B50-2573-OOIT)
Protectioncover
(H20-0439-03)
Carton case (Inside)
(H01-2564-04) (KW)
(H01-2566-04) (T)
Cartoncase(Outside)
(H03-1664-04) (K)
(H03-1666-04) (T)
15

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