X-2 Technical Service Manual Adjustments 7-5
Publication No: 15-02047
7.6.3 VCO2 Adjust
108-04840
To adjust VCO2:
1. Select Test Mode (refer to Section 7.5).
2. Select channel position 8 and USB/LSB to LSB.
3. Short together TP11
[D7]
and TP12.
4. Connect an Oscilloscope to TP13
[D6]
using the following settings:
• Y input to 5 V per division (0.5 V/division if using 10X probe)
• Timebase to 2 µs per division.
5. Commencing from the bottom of the coil, adjust L15
[C6]
tuning core for
minimum repetition rate. Remove the short from TP11 and TP12.
ICAUTION
Great care must be taken to use the correct trimming tool to prevent
damage to the tuning core.
6. Select channel position 9.
7. Connect a DC voltmeter to TP13. Commencing from the bottom of
inductor L17, adjust the tuning core for a reading of 3.0 V ± 0.2 V.
Frequency at TP10 should measure approximately 44.5405 MHz.
8. Select channel position 8.
9. Check the voltage at TP13 reads 8.0 V ± 1.5 V. The frequency at
TP10 should measure approximately 44.5443 MHz.
10. Select channel position 10.
11. Check the voltage at TP13 reads between 11.0–15.7 V. The frequency
at TP10 should measure approximately 44.5485 MHz.
7.7 45 MHz Filter Alignment
108-04840
There are two methods of aligning the 45 MHz roofing filter located on the
Rx/Exciter & Control PCB:
1. Using an Oscilloscope and a Signal Generator.
2. Using a Spectrum Analyser with Tracking Generator.
Both methods are detailed in the following two sections.
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