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4 40000-60080:
4.1
GENERALINFORMATION
The VFO-820 consists of a VHO unit, a switch board, and an indicator board
mounted on the main chassis.
Figure 4 shows the block diagram of the VFO.
4.2.
VFO
UNIT
(X40-1110-00)
The VFO
unit is the same
as the VFO
unit of the TS-820.
The circuit is a
Clapp oscillator using field effect transistors, combined
with a three-stage
transistorized buffer amplifier, for stability against load fluctuations.
The
oscillator
frequency
ranges
from
5.0
to
5.5 MHz.
The
angular
displacement of the main tuning dial is reduced through a series of gears so
that one revolution of the knob is equivalent to about 25 kHz.
The RIT circuit allows tuning of the receive frequency without changing the
transmit frequency.
4.3
INDICATOR
BOARD
(X54-1180-01)
This board controls the light emitting diode indicators.
When the VFO-820 is
controlling operation
the VFO
light is turned
on.
When
the RIT circuit is
switched
on the RIT indicator is lighted.
4.4
SWITCH
BOARD
(X41-1080-00)
This board holds the control circuit, FUNCTION
switch, and control relay.
SECTION
4. CIRCUIT
DESCRIPTION
HUDD~eEUND~cO0NDD-CEUED- HELD -CURNED~COUEDDHCHONDD<COBEND~<OUNDD>CUNDED=COUEDDHCUDOND+cOE0NDHcUNUD~¢O00UD=000000=¢O0UND-C000DD>4O000-e00N00~¢0UFED~O0NDH+CHU0D=cOUNEDHC0NODD=<O0U0D-CONNDD=cOONUD=c00ND-cOU0UD-cHUND-cUNdOr-neeun-cunnnn=cnnenr-cungn:
s
VFO UNIT X40-1110-00
VFO OSC
Q1
Buffer Amp
3SK22
!
Buffer Amp.
Buffer Amp.
|
VFO
OUT
cea
Or ca hate
ae ae A Sa
RIT
Control
9V
IN
Pe TRANSCEIVE
9V OUT
ES!
_ Cone
(MAIN VFO)
SWITCH BOARD L ___——
VFO CAL
X41-1080-00
INDICATOR
BOARD
X54-1180-01
Fig. 4 Block Diagram
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