Hi Bruce,In fact, I think we're at a similar level here! One thing I might suggest regarding the oscillation issue is to get the antenna matching as close as you can, especially tuning out any reactive component.
I took a closer look at my setup yesterday, using the scope, and noted that the waveform is quite messy at higher drive levels, or suffering severe crossover distortion at lower drive. I'll work more on the biasing arrangement of the finals. The waveform has a high frequency "ring" that I suspect is due to resonance in the OP transformer when each transistor shuts off current abruptly. This is seen with the antenna, or a simple dummy load.
On the loop antenna I should add a correction to my first post. It's impedance at resonance is 800 Ohms (not 8000 as stated). Thus, a 16:1 impedance transformer gives the best match to 50 Ohms, a fact supported by SWR measurements, and experiments with different turns ratios on the matching transformer.
Happy tinkering to you!
Ed