LF, Roger,
Mal gave some insightful comments re: Class-E
I have also used a class-E amp on 500kHz,and I echo all the comments
about careful choice of FET and of the output tuning/loading to get the
correct drain waveform.
My usual contraption uses a single IRF150 (a TO3 cased 100V/18A SMPSU
device) at 100W output. I've never had any trouble with this device
expiring, even when running on a 30V PSU, with the peak drain/source
volts flirting dangereously close to the 100V device limit.
I've run a beacon occasionally overnight, at 100W (200mW ERP from my
small vertical) and come down in the morning to find the antenna in
disarray, capacity wires flapping in the wind, SWR sky high, and the
IRF150 still going strong (if a little warm!)
For antenna adjustment I wind the variac down to get 10W output and can
happily keep a carrier on while I visit the antenna field and adjust the
atu (including disconnecting the feeder to insert a reflected power meter).
I did try a pair of IRF640 in parallel in Class-E and acheived 200W.
They weren't quite so forgiving though, and expired in a shower of
sparks when I accidentally removed the antenna connection....
John
GM4SLV
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