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Ref recent discussion on the subject.
I use a class E pa on 500 kcs and never get any
trouble.
As a general guide use high voltage fets and the
fet V should be rated at about 5 times the supply V and current about 3
times.
You arrive at class E by careful design not by
accident.
Having designed and built the PA for the required
power and load R usually 50 ohms adjust into a DL for correct waveform
as displayed on a 'scope, this is important otherwise V spikes and instability
will kill the fet.
Install a suitable antenna and match it with a
suitable atu to 50 ohms so when you connect the TX/PA to the antenna they both
match.
Check the wave form again and any slight mismatch
should be adjusted by the antenna atu and NOT the pa.
The load does not
have to be 50 ohms but this is convenient when testing with available test
gear.
High V fets give more realistic C and Inductor and
R values. A good range for fets is a psu giving 40 - 100 volts ie fets 500volts
and a suitable current rating depending on your power. requirements ie if you
need to draw 5 amps the fet should be rated 15 amps.
These are the general guidelines and work well for
me.
Most amateurs seem to use class D amps whereas
class E are rare.
de Mal/G3KEV
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