Section III
Paragraphs 3-1 to 3-4
SECTION III
THEORY OF OPERATION
3-1. GENERAL SYSTEM OPERATION.
stages are coupled by phase shifting networks consist-
ing mainly of C-1401, R-1401, C-1402, R-1405, and
3-2. The r-f section of the unit supplies the r-f
C-1403, R-1408. The phase shifting networks have
carrier by mixing the outputs of two crystal controlled
60 phase shift perfection at 30 cps and a total of 180'
oscillators and multiplying the sum frequency tothe
phase shift. The net phase shift introduced by the
desired 108.0 to 135.9-mc output frequency. (See
three tube sections is also 180, thus, when the output
of V-1402B is fed back to the grid of V-1401B the feed-
modulating the r-f carrier are generated in the audio
back is in phase and the circuit operates as a 30 cps
section by stable RC oscillators and fed to the audio
oscillator. Dual potentiometer R-1410 in the inter-
selector switch. R-F output in the 329.3 to 335.0-mc
stage RC coupling circuits allows approximately 1 cps
range is obtained by mixing the 129.3 to 135.0-mc
change in the 30 cps frequency and provides the f rent
signal with a 200-mc signal from a crystal controlled
FREQUENCY adjustment.
Each of the
injection oscillator in the univerter.
phase shifting networks has a temperature compen-
sating network connected in series with it. The paral-
3-3. DETAILED CIRCUIT OPERATION.
lel combination of R-1580 and R-1581, for example,
is used to temperature compensate the C-1401, R -1401
3-4. 30 CPS OSCILLATOR. The 30 cps oscillator is
phase shifting network. R -1581 is a negative temper-
an RC type oscillator using three stages each having
ature coefficient resistor which is connected in paral-
a gain of approximately two. See figure 9-1. These
lel with R-1580, a resistor having a negligibly low
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