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Dear OM's
I was pondering over using the horizontal
TV-deflection system as a PA for LF. By stretching the flyback time to 50
percent of the period, using a push-pull stage with two identical circuits
and then subtracting both outputs from each other should give a nearly perfect
sine-output.
So I breadboarded a test circuit with two
IRF730 FET's and after ample experiments it resulted in over 50 W RF on 136 kHz
in a 50 ohm dummyload with 70 V dc input. Efficiency proved to be over 90
percent. Vdrain was abt 260 V peak and Isource of each FET was abt 2.2 A peak,
both well within spec.
Measured with a spectrum-analyser: even
harmonics were more than 40 dB and 3rd harmonic was 23 dB below
fundamental.
Is this contraption already known yet
as an LF-PA ??
If so, then:
1) What class of operation is it ?
2) I re-invented the wheel.
Thanks in advance for your
comments
73 frm
Harry, PA0LQ since 1946.
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