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Page Title:
Figure 4-16. 81.25 MHz Bandpass Filter Adjustment |
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|  TM 11-5820-873-34
NOTE
The following adjustment involves three
interacting components.
Due to this
interaction
the
adjustment
of
each
component should be repeated until
maximum output is obtained.
(f) Adjust 1A4A3L20, then L36, and then L21
for maximum RF voltmeter indication.
(g) Remove isolation pad connected between
L20 and ground. Remove jumper from between junction
of 1A4A3Q8, R71 and ground.
Figure 4-16. 81.25 MHz Bandpass Filter Adjustment
NOTE
Setup #2
The following adjustment involves three
NOTE
interacting components Due to this
The following adjustment involves two
interaction
the
adjustment
of
each
interacting components.
Due to this
component should be repeated until
interaction
the
adjustment
of
each
maximum output is obtained.
component should be repeated until
(h) Carefully readjust L20, L36 and L21 for
maximum output is obtained.
maximum RF voltmeter indication.
(f) Carefully readjust L7 and L8 for maximum
(7) 81.25 MHz Bandpass Filter Adjustment
VTVM indication. Minimum acceptable output is 40 mV.
(1A4A3)
(8) To adjust Output Level, connect oscilloscope
(a) Jumper Junction of 1A4A3Q11 gate # and
to 1A4A3-15. Set front panel FREQUENCY switches to
R14 to CCA ground. Connect VTVM (AC) to 1A4A3-TP2.
29.9999 MHz. Adjust 1A4A3R54 for 600 mV peak-to-
peak.
MHz. Set signal generator output level to 250 mV.
(9) Remove card extender and reinstall Translator
Connect signal generator as shown in Figure 4-15.
1A4A3. Reinstall Synthesizer protective cover. Reinstall
receiver-transmitter top cover. Remove dummy load.
d. VHF VCO CCA 1A4A 5Adjustment.
(1) Remove receiver-transmitter top cover.
Remove Synthesizer protective cover Remove receiver
transmitter bottom cover.
Remove six front panel
mounting screws. Lay front panel forward. Connect a 50
ohm dummy load to receiver-transmitter ANT jack. (See
CCA 1A4A4.
(2) Band "O" Adjustment
(a) Connect frequency counter to 1st Local
Oscillator output 1A4A5J1 Inject + 1.95 VDC, from a
Figure 4-15. 81.25 MHz Bandpass Filter Adjustment
bench power supply, at 1A4A5-4.
Setup #1.
(b) Set front panel 10 MHz and 1 MHz
(b) Adjust 1A4A3L8 for maximum RF
frequency selectors to 0. Adjust 1A4A5L1 for 91.75 0.2
voltmeter indication.
MHz.
(c) Connect signal generator as shown in
(c) Set front panel 1 MHz frequency selector
figure 4-16. Frequency setting remains at 81.25 MHz.
only, to 9. Adjust 1A4A5C16 for 100.75 0.75 MHz.
(d) Repeat steps (b) and (c) above until both
NOTE
frequency
adjustments
are
within
tolerance
The following adjustment involves two
simultaneously.
interacting components.
Due to this
(3) Band "1" Adjustment
interaction
the
adjustment
of
each
(a) Connect frequency counter to 1st Local
component should be repeated until
Oscillator output 1A4A5J1. Inject +1.95 VDC, from a
maximum output is obtained.
bench power supply, at 1A4A5-4.
(d) Adjust 1A4A3L7 and then L8 for maximum
(b) Set front panel 10 MHz frequency selector
VTVM indication.
to
(e) Remove isolation pad connected between
L7 and ground. Remove jumper from between junction of
1A4A3Q11, R14 and ground.
4-42
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