Are there any proven reliably designed LF amplifier designs power
amplifiers for 137 / 475? Wideband, covering both ideally
Rated for at least 300 Watts output, and ideally a lot more.
I saw G3YXM's low-HF design, and it looks promising for low frequency use,
but he appears to have not gone that way and went for a switchmode version at
LF/MF
Of course, I could just redesign that, or something similar, using suitable
ferrite and a bit of feedback ,but it would be nice to avoid reinventing too
many wheels.
Using switching MOSFETs as linear amps still doesn't feel quite right, but
enough people seem have managed it now (including my own design for a low power
one) that it looks a sound-enough route to follow up. The one thing
that does bother me about the technique is bias compensation with temperature.
It is really asking for active bias control, but in a class-B or -AB
design, where bias just affects standing current, that gets more-than a bit
tricky as a concept.
Andy G4JNT
