LF/MF
In my 500 khz class E amp I use a 1.150mH choke and it works well. This is
what was available in my junk box, and larger than the calculated value. It
is better to err on the high side. After designing a class E pa to suit your
requirements, voltage availability etc the fun begins setting it up
correctly.
I consulted N O Sokal/WA1HQC publication and was able to get mine spot on.
Page 16 of his document shows the various waveforms for correct and
incorrect alignment when using an oscilloscope. It is important to get it
exactly right if you want your FETS to survive, otherwise the transient
spikes will kill them eventually. Once set up correctly forget about
waveform monitoring, except you make changes to matching and antenna
loading.
I check my waveform periodically but it never varies since I have made no
alterations to the antenna matching system or antenna. My PA is designed to
match 50 ohm loads.
There is plenty of info available for building a class E amp, follow the
instructions carefully and avoid SMOKE.
73 De Mal/G3KEV
|
