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5.3 Synthesizer Adjustment
If a frequency was assigned, all adjustments have beenmade at the
factory. If no frequency was assigned, or if a change in frequency
is made, the following-procedure should be completed.
Select the correct AM Oscillator PWB, Synthesizer Programming
PWB, and RF Output Filter according to the following table of
Synthesizer Bands.
Rotate the programming switches to the desired operating
frequency. See drawing for "Synthesizer PWB Assembly". For
example, to select 250 KHz, rotate S1 to 2, rotate $2 to 5,
and rotate $3 to 0. S4-1 and $4-2 should both be OFF. For
250.5 KHz, place S4-1 in the ON position. For 1250.5 KHz, place
$4-2 and $4-I in the ON position.
Attach a voltmeter to TP4 (Error Voltage) and TPI (Ground).
For best results, the voltmeter should be a high-impedance
digital voltmeter, however, satisfactory results may be
obtained with a 20,000 ohm/volt VOM.
Check that the RF DRIVE control on the AM Oscillator PWB is
fully CCW.
Connect the jumper on TB4 from Terminal 1 to
Terminal 2.
5.
Apply power to the transmitter.
Note the voltmeter reading. If the voltmeter reads 0, the LC
oscillator is tuned above the selected frequency and beyond
the phase-lock capture range.
If the voltmeter reads
approximately 8.5 to 9 volts, the LC oscillator is tuned below
the selected frequency and beyond the phase-lock capture range.
If the voltage is between 0.5 volts and 8 volts, the LC
oscillator is locked to the reference oscillator and is on the
selected frequency.
Adjust L1 by rotating the tuning slug to bring the oscillator
frequency within the phase-lock capture range.
NOTE: L1 is at maximum inductance when the tuning slug is flush
with the top of the coil housing.
Adjust L1 for a voltmeter reading of 5.0 volts. The lock
indicator LED~ DSI, should be lit at this time if a high
impedance voltmeter is used. If a 20,000 ohm/volt VOM is used,
it will be necessary to remove the test lead from test point
TP4 before the lock indication LED will be lit. Because stray
SS-800AVS
Southern Avionics
Company
95
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