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Page Title:
If. Preamplifier, Detailed Analysis |
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|  range from 442- to 742-mc. Because of the
increase the signal output from the rf tuner
before the signal is applied to the if. step
greater physical length needed for the two
p a r a l l e l transmission lines, a capacitor
a t t e n u a t o r . This preamplifier, which is
( C 5 2 4 ) is connected between the trans-
i d e n t i c a l in function and circuit values
m i s s i o n lines to electrically lengthen the
l i n e s . Capacitor C225, connected between
c o n s i s t s of one cascode driver-amplifier
stage and two if. voltage amplifiers. Sep-
t h e plate and the cathode, assures sus-
arate connectors at the input to the if. pre-
tained oscillation throughout the frequency
amplifier receive the incoming signal from
range.
the 700-1,000-mc tuner and the 400-700 -
m c tuner. The position of a microswitch
T h e functioning of the crystal mixer cir-
(S502) which is driven by a cam on the band
cuit is idential with that of the 700-1,000 -
selector switch creates a dc path of conti-
m c tuner except for the use of reference
nuity from the operating rf tuner to the in-
symbol CR502 as the crystal diode, C523
p u t cascode driver stage, V505A. Except
a s the rf bypass capacitor, and L514 as
for this microswitch and the different
t h e crystal mixer coil. Cable termination
r e f e r e n c e symbols employed, the circuit
CP502 is used to couple the 42-mc if. out-
analysis for this if. preamplifier is
put signal through a short length of coaxial
identical with that for tuning unit 3 (para
cable to connector jack J509 on the 42-mc
i f . preamplifier subassembly.
out only the differences in reference
symbols between the two if. preamplifiers
55. If. Preamplifier, Detailed Analysis
s o that identical functioning parts can
A three-stage preamplifier is used to
easily be located.
79
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