15
5. DMD Level (R25). With conditions the same as in IF Alignment apply a standard
centered LOC modulation and adjust R25 for .35 Vrms on DMD output.
E. COMM Receiver (Dwg. SS1866)
1. Apply +15 vdc and –30 vdc to appropriate input leads, set local oscillator signal to 3
+/-2 dbm and a 1 to 15 vdc variable voltage source to Vt.
2. IF Alignment (L2, L3, L4). Apply +10 vdc to Vt, 135.975 MHz at –90 dbm to RF and
157.175 MHz to L.O. Adjust L2, L3 and L4 for minimum voltage reading on Vagc.
Apply amplitude modulation of 30% and frequency is adjusted from 1.0 to 12.0 KHz the
DMD level shall be constant +/- 1 db. Adjust L2 and L3 as necessary to keep DMD level
constant.
3. RF Alignment (T1, T2, L1, T3). With conditions the same as in IF Alignment but
modulation set to 0, adjust turn spacing on T1, T2, L1 and T3 so that Vagc reading is a
minimum.
F. NAV Synthesizer (Dwg. SS2714)
1. Apply +15 vdc and 1 MHz to appropriate module input. Set R3 to midrange.
Digitally input, using Computer board or equivalent, the proper coding for 96.50 MHz.
Verify correct output frequency. Adjust turn spacing on T1 so that Vt = 7.00 vdc.
Digitally input coding for 86.60 MHz. Vt shall be 2.50 +/- .30 vdc.
2. Digitally input coding for 91.60 MHz and monitor output on a spectrum analyzer.
Adjust R3 so that 50 KHz sidebands are nulled.
G. COMM Synthesizer (Dwg. SS2716)
1. Apply +15 vdc and 1 MHz to appropriate module input. Set R3 to midrange.
Digitally input, using Computer board or equivalent, the proper coding for 157.30 MHz.
Verify correct output frequency. Adjust turn spacing on T1 so that Vt = 10.00 vdc.
Digitally input coding for 139.40 MHz. Vt shall be 5.00 +/- .50 vdc.
2. Digitally input coding for 149.00 MHz and monitor output on a spectrum analyzer.
Adjust R3 so that 25 KHz sidebands are nulled.
H. Transmitter (Dwg. SS1881)
The Transmitter does not normally require alignment but tests should be performed to
verify proper operation.
1. Connect the transmitter to a properly aligned COMM Synthesizer and connect a 50
ohm load to the Transmitter output. Monitor the output power level to verify that it is at
least 9.0 watts without modulation across the frequency range of 118 to 136 MHz. Apply
at least 80% modulation at 1.0 KHz and monitor the output with a spectrum analyzer to
verify that no parasitic oscillation is present. If problems are encountered, consult the
factory.
To Next Page
Loading...
