TROUBLESHOOTING AND REPAIR
FREQUENCY SYNTHESIS
PROCEDURE:
The SSB Mixer LO Power, as measured with a 10X RF probe using a spectrum
analyzer, is adjusted to -10 dBm as displayed on the spectrum analyzer. This
corresponds to +10 dBm at the input to the coupler.
1. Program the UUT to SPCL 909.
2. Program the UUT to 800 MHz.
3. Connect the 10X RF probe to the input of the spectrum analyzer. Set the spectrum
analyzer to -5 dBm reference level, 160 MHz, 1-MHz span, and 1 dB/div.
4. Touch the probe tip to input of the coupler, U52, that connects to C147. This is best
done on the top of the coupler with the ground connection on the coupler ground
plane.
5. Adjust R106 for -10 dBm as displayed on the spectrum analyzer.
10-kHz Notch Adjustment, L56 6C-10.
TEST EQUIPMENT:
• Spectrum analyzer
REMARKS:
The 10-kHz Notch Adjustment is normally required only when L56, L57 and
associated components have been replaced or the adjustment has shifted.
PROCEDURE:
A signal from the internal modulation oscillator is injected into the Sub-Synthesizer
phase detector to produce a 10-kHz spur. L56 is adjusted to minimize this spur.
1. Program UUT to SPCL 909.
2. On Sub-Synthesizer VCO (A3), move jumper (near J2) from TP1-TP2 to
TP1-TP3. Replace the cover on this side of the module.
3. Program the UUT to 800 MHz, Modulation Frequency 10 kHz, Modulation Level
to 100 mV. Connect the front panel mod out to TP36 on Sub-Synthesizer PCA.
4. Set spectrum analyzer to center 160 MHz, reference level 5 dBm, frequency span
100 kHz. The signal should be visible in the center of the screen with 10-kHz
sidebands.
5. Adjust L56 to minimize these 10-kHz sidebands.
6. On the Sub-Synthesizer VCO (A3), move jumper (near J2) back to TP1-TP2.
6C-15
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