Total posts : 45366
There is no question that designing an AM tx. to match the variety of loads presented by part 15 AM antennas is a challenge due to the unpredictability of the load Z. Thanks for running some ideas by us here, and I hope Lee (original poster) will forgive us for getting off topic, but maybe we’re coming back a bit.
Just to help you follow some of what I posted, the SSTRAN circuit is very similar to the first Wenzel circuit at this link:
The Ramsey AM-25 uses a Tmosfet (MTP-3055) as the final in a class C circuit followed by a seven pole LPF (which may also be the matching network). The maximum efficiency I have measured on my unit is 31% into a bench 24 ohm resistor. This interests me since the feedpoint Z of a resonant SSTRAN type antenna is in this range of Z.
As you think about Litz wire for inductors in the circuit, it seems to me that the R of the ground system may swamp this resistance advantage over regular magnet wire but perhaps the numbers need to be crunched to find out for sure.
I hope this helps somewhat as you ponder a circuit. Your comment about fiddling with parts rings true with me though I usually know why they are there….just don’t always know their values. I recall a VHF amplifier I built on a ground plane where the dress of the capacitors in the output network made a hugh difference in the gain. I tuned it by bending them toward or away from the board.