I wasn't quite satisfied with the long-term stability of my VFO. It seemed like it was drifting about 70 Hz per hour, even after the initial warm-up period. So, all out of Q-Dope, I went to the local pharmacy in search of clear nail-polish. (My family was making fun of me.) I got home and applied several coats of "Sally Hansen No Chip Top Coat Vernis de Protection." I let it dry a bit, then started watching the frequency counter. At first results were disappointing. Drift continued. Now it seemed to be drifting up! I cracked the books. EMRFD has a good chapter on temperature compensation of VFOs, but the process seemed painful. I wasn't looking forward to it.
I left the VFO on when I went to work, noting the freq as I departed. Ten hours later I returned, and was delighted to find the frequency almost exactly where I left it! It may have taken a while for the nail polish to completely dry. I'll leave it running again today to see how it does.
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Dan sheds light on various Hammarlund SP-600 models - Many thanks to SWLing Post contributor, Daniel Hawkins, who leaves the following comment in reply to our previous post about the Northern Radio SP-600 and ...
1 hour ago