My prime reason for opting for Class D was a shortage of big variables around here. What I forgot about was the fact that my high level antenna tuner does not cover 160. This came as a dull thud when I was ready to move off the dummy load.
I have an L-net type tuner I made to use my 80 m dipole on 160 so this is the first thing I tried. I got a nice SWR null with it on my 160 dipole but the waveform was not a clean sine but the guy I contacted with it said it sounded great. Ignoring that, what was interesting is that tuner uses a loading type variable (close spacing) and produced no arcing at all.
I then substituted my low power MFJ tuner which nulled out and produced a clean waveform at 100 and 200 W. I did not modulate it as it is rated at 300W.
I opened up the MFJ and measured the C's and L and replicated this with larger caps but they arced with 100W and no modulation. The injput C required is about 126pf but the largest cap (3/8" spacing) I own was only 100pF so I put back the MFJ after setting the input cap to 100 and measured the L and other C when this nulled.
Using this cap in the tuner, it arced over when I modulated at 100W.
Somehow, I am building some sort of high voltage transformer instead of an antenna tuner and it's time to start over.
The obvious question at this point is, what is the difference between a tuner with Class D and the output tuning of Class E? All I want to do is load a 160m dipole with this transmitter.
I notice Steve's 400W Class E has 1:1 transformer, L input and two caps for tuning and loading.
If I change my output transformer to 1:1 and replicate this network, will I accomplish what I need?
There are lots of neat calculators on line to help design these sorts of networks but they all want parameters that I have no idea how to determine.
For example, they want input resistance and reactance to calculate input Z and likewise for the output. I presume I can use the numbers from my antenna analyzer to get the output but the input is a mystery. All I know is the DC resistance but don't know what the transformer does to this nor where to get the reactance.
I guess I am rambling but perhaps there is s nugget in here somewhere.
js