On key-up, the keying transistor Q1 is switched off, and the C1 capacitor is also supposed to mop up any RF leakage too. However some RF *still* can leak through to the antenna! It's many many dB down but if condx are good, QRSS'ing can detect that stuff. Keith G6NHU sent me a beautiful screenshot of slow-hell on the v2.02 and there was a faintly visible carrier between words and between messages. Admittedly it was a very strong signal and only just across the North Sea. But by moving the frequency to 6.25MHz during key-up on Hell spaces or between Hell messages, I could eliminate that faint key-up carrier. It was just a single function call and would fit into the last few remaining bytes so I did it!
FYI 6.25MHz is what is used for the calibration of the 125MHz canned oscillator when a GPS is connected, in the 13 seconds before the start of a frame. 6.25MHz is 125MHz divided by 20. By measuring it for 10 seconds I am able to determine the 125MHz frequency +/- 2 Hz, which is good enough.?
