[Collins] S line fx error

[Dr.Gerald Johnson]

There is only one place to look when the transmit frequency doesn't 
agree with receive in the transcieve mode. The BFO crystals. Check 
its error on the other side band, it should be different. Ideally for both 
transmit and receive the BFO crystals should be at the 20 dB down 
points of the mechanical filters and should be on the same frequency. 
Checking the receiver crystals with respect to the filter is relatively 
easy using the calibrator signal and seeing how far zero beat is from 
20 dB down on the S-meter. Transmitter checking is more difficult, may 
take a counter. Neither the transmitter nor the receiver has any 
provision for adjusting the crystal frequency which makes 
replacement the most common solution. It may be possible to 
change the grid to ground capacitor if the crystal has drifted high in 
frequency, but that won't help if the crystal has drifted low. There was 
a source of crystals posted here in the past couple weeks.

73, Jerry, K0CQ, Technical Advisor to the CRA

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.