I finally got to smoke test the transmitter today. After some trial and error on the input matching for the driver stage I got around 25W out of the radio. I can't see any way to increase this without another stage so I am adding one more stage in the near future.
Harmonics will be a big issue. The second harmonic is around 10dB down, the third around 20dB down. While some improvement can be expected when the low pass filter is rebuilt, I don't expect it will be good enough in the current form. I know the harmonics are already present in the exciter output, so my plan is to put a band pass filter after the exciter and before the pre-driver that I will incorporate into the transmitter.
The good news is that the matching sections from the collector of the driver stage onwards all appeared close to correct. The output of the exciter did not appear to be a good match to 50ohms hence I had to re-jig the input matching to the driver on the run. Since I will have plenty of gain with another stage I will pad the output of the exciter with a 5dB or so attenuator to make it look like a better match to the filter I will build.
73's
Richard
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