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
