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CIRCUIT DESCRIPTION
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*Coil Pack Unit (X44-1230-00)
The Coil Pack Unit is the same basic design as that used in
the TS-820 transceiver, excepting the RF section, which is.
double-tuned for higher selectivity.
*RF Unit (XX-1240-00)
The RF Unit consists of an RF amplifier, 1st mixer, and
block bias circuits, and assembles to the Coil Pack Unit.
*IF A Unit (X48-1190-00)
The IF A Unit consists of an 8 pole crystal filter for 8830
kHz, filter and gate circuits for the noise blanker, 2nd mixer,
ceramic and crystal filters for the 2nd IF at 455 kHz, 3rd
mixer, S-meter amplifier, and filter preset switches.
The standard supplies filters pre a YG-88SW (8830 kHz)
and CFJ455K3 (455 kHz) both for SSB, and CFR455H for
AM. Optional filters are the YG-88A (AM) and YG-88C
(CW)
both for the
1st IF, and YG-455C (CW) and
YG-455CN (CW) both for the 2nd IF.
*IF B Unit (X48-1200-00)
The IF B Unit contains 3rd IF (50 kHz) circuits, consisting of
the notch filter, notch filter switch circuit, product detector,
AM detector, switching AM detector switching circuit, and
AGC amplifier.
*NB Unit (X45-1330-00)
The NB Unit consists of a noise amplifier for noise blanking.
*AF AVR Unit (X49-1080-01)
The R-820's AF AVR Unit is identical to that of the TS-820
transceiver, and includes the audio power amplifier, 9V
regulated power supply, FET bias supply, and RIT adjust
circuits.
*PLL Ass'y Unit (X60-1010-01)
The PLL Ass'y Unit consists of the PD (Phase Detector) Unit
(X50-1 340-01) and the VCO (Voltage Controlled Oscillator)
Unit (X50-1 330-00).
The R-820 has a front panel switch for turning the HET
oscillator on and off; for transceiver operation, HET output
accepted from the TS-820 forms the PLL loop.
The PD Unit has separate crystals for each band, two
mixers, waveform shaping, and phase comparator.
It
generates control for the VCO, based on BFO output. It
also provides a pure electronic IF Shift loop by using the
incoming carrier signal.
The VCO Unit contains the voltage controlled oscillators for
each band, buffer amplifier, and oscillator output shut-off
circuit
for
loop
unlock.
Oscillation frequencies are
controlled by voltage from the PD Unit. Band switching for
both units is by electronic (diode) switches.
*CAR Ass'y Unit (X60-1040-OO)
The CAR Ass'y Unit consists of IF Shift and VBT control
circuits, and a local for the 2nd mixer.
The CAR-1 Unit (X50-1480-00) has an oscillator for IF
Shift, crystals for 8831.5 kHz (USB) and 8828.5 kHz (LSB).
switch circuit, and VXO circuit. It also contains an oscillator
frequency shift circuit for AM 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 and VXO circuit.
* Local OSC Unit (X50-1440-00)
The Local OSC Unit accepts signals from CAR-1 and 2 to
produce a 455 kHz mixed output, and also produces a 505
kHz signal by mixing the 455 kHz mixed output with the 50
kHz NOTCH signal generated by its own oscillator. It also
has 50 kHz signal generator. The 50 kHz signal is used as
a BFO signal for the product detector, and the 505 kHz
signal is used as a local signal for the 3rd mixer.
*FIX Unit (X50-1450-00)
The FIX Unit consists of an oscillator for the 4 fixed
channels, and a —6V power supply for block bias.
* Indicator Unit (X54-1180-00)
This unit provides "VFO", "FIX", "RIT", and "NOTCH"
indication. The VFO and FIX indicators also function during
transceiver operation with the TS-820.
*VR ASS'y (X54-1340-00)
The VR Ass'y has variable resistors for monitor level control,
NB level control, and tone control.
* Switch Ass'y (X41-1130-00)
During
full transceive operation, the TRCV
activates the VFO and HET switching circuits.
position
* Relay Ass'y (X43-1190-01)
The Relay Ass'y consists of a standby relay, low voltage DC
p.ower supply capacitors, and the 5-volt stabilized power
supply for the PLL circuit. The standby relay switches block
biases and VFO power during transceive operation.
*VFO Ass'y (X40-1110-00)
The receiver's overall frequency stability depends on that of
the VFO, since the PLL circuit is controlled by VFO output.
VFO frequency is 5.0 MHz to 5.5 MHz.
*5V-AVR Ass'y (X43-1220-00)
The 5V-AVR Ass'y supplies regulated 5V DC to the Counter
ass'y.
* Marker Ass'y (X52-0005-01)
The 100 kHz synchronizes output from 01 is waveform
shaped by diode D1, Q2 and Q3 multivibrator. The 25 kHz
multivibrator output is amplified by 04 and fed to the
receiver input.
* Counter Ass'y (X60-1020-00)
The Counter Ass'y consists of the Counter Mixer unit
(X54-1150-00) and the Counter unit (X54-1160-00), both
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