Last weekend I found some time to continue with my QRP transmitter project. I played a little bit with the output filter and ended up with this schematics:
A 100p capacitor offers around 1 – 4 kHz tuning range, depending on your chrysal. I noticed that the old FT-243 chrystals have only a very narrow tuning capapility. Unfortunately the suppression of the 2nd harmics in the 20m band is not good enough. So I will have to change the output network again. So that part is not quite finisched but I put the transmitter into a nice housing:
I used a Hammond case instead of the “Altoids box”. It is more robust and sometimes you can get Hammond boxes or similar from ebay quite cheap. Now the small transmitter is ready for first tests on the air ( with an additional filter of course ).