I've had my Push-Pull Colpitts on the air now for about 3 weeks and 10 QSOs. Notable QSOs have included my friend Lou, VE3AWA, in Ontario and W0NYQ, a fellow Minnesotan with a big interest in '29 rigs.
This tranmitter is a keeper. Why?
- Efficiency is 50-60% (great for a '29 power oscillator)
- Drift is measured in the 10s of hertz range. Essentially solid as a rock.
- No hand capacity problem when tuning to get on frequency
- Easy to adjust feedback for minimum plate current and best performance
- "Perfect sounding 1929 signal"
I did receive a report of a trashy buzz on my sidebands. Since then I've been more careful when adjusting the feedback and also the output coupling. I haven't had any other bad reports.
I do still have some trouble with FMing/wobble due to the wind blowing around my antenna. This is a common problem with '29 power oscillators. Whether this is an improvement over my other '29 transmitters, I can't tell.
I haven't cleaned it up on 40 but I can work on that later.
All in all, a really satisfying project.