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Page 299
CIRCUIT DESCRIPTION
The function of this circuit is
to
amplii
the3.396
MHz
IF
signa!, mix
it
with the premix injection to the desired output
frequency, and amplify this signal to the level required by
thedriver (circuit board
J).
lC3Ol amplifies the IF signal. Q303 and associated
components provide
ALC
control, which is applied to IC301
to control transmitter gain. Q302 samples the ALC voltage
and drives the front panel meter to indicate ALC action.
0301
is
an emitter follower, used to match the input
impedance of the balanced mixer.
Diodes
D306, D307. D308, and D309 form a balanced
mixer, which combines the IF signal and the premix signal
to
create an orrfreguency transmit signal.
The
output
of this
mixer is filtered by diode-selected
bandpass filters and
applied to the input of the predriver.
I
I
0304 and 0305 form the predriver circuit. Transmitter
I
keying in
CW
is
accomplished in this circuit by switching the
,.
emitter DC return on and off. The output of the predriver
is
filtered by diode-selected bandpass filters.
U21 and the 470 PF capacitor at the output form a 3.395
MHz
trap, used to reduce the amplitude of a spurious output
at that frequency on 80 meters.
1
I
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