CIRCUIT DESCRIPTION
TRANSMIT BOARD
ALIGNMENT PROCEDURE
U50IC is an amplifier whose gain is controlled by
the level
of
audio entering the rectifier at pin 16.
As the level here increases, the gain is decreased
and this results in a2:1 compressioncharacteristic.
Pre-emphasis is added by U501B. R504, R505,
and C508 setthis at 115uS. C531 rolls the response
offabove
10KHz
to
further attenuate the 20 KHz
call signal (see Audio Board Circuit Description).
Q501 is aColpitts oscillator with the collector
tuned
to
the third harmonic. T501, VVC501 and
VVC502 are added in selies with the crystal
to
allow frequency modulation
of
the oscillator. The
oscillator is operated
10KHz
below the series
resonant point
of
the crystal. This improves
linearity at the expense
of
somestability. Q502 is a
trip1er and Q503 is astraight through amplifier.
ThecatTier frequency is thus nine times the crystal.
C529, C530 and L503 function as alow pass filter
and matching network.
3-2
EQUIPMENT
REQUIRED:
oRF POWER METER
oFREQUENCY COUNTER
oDC VOLTMETER
1.
Connect the RF power meter and frequency
counter
to
the Transmit Antenna jack. Make
surethe Transmit switch
on
the
reat·
panel is set
the the Cont position.
2.
AdjustT502, T503, T504, VC501, and VC502
for maximum power. Note:
If
adjustments are
severly out
of
alignment and no output can
be
obtained, it may be necessmy
to
first adjust
T502and T503 for maximum DC voltage at the
emitter
of
Q502. Then adjust T504 for maxi-
mum
DC
voltage at the emitter
of
Q503. Now
adjustVC50 1and VC502for maximum power.
3. Adjust T501 for the
COlTeCt
frequency:
Y501 Marking Frequency
154T570 154.570
177T800 177.800
183T730 183.730
4.
Repeat Steps 2and 3as necessmy.
5. Deviation
will
be adjusted
in
the audio board
alignment.