Clemens wrote:
> I would recommend feeding DC not via the center tap ...
> ... Instead I would feed DC via two separate DC chokes.
I understand. I've seen that arrangement in circuits of
HF PAs and wondered why it was done that way. It would
simplify the primary winding too.
Thanks for the tip, I will certainly do that, I've got a
couple of suitable chokes pulled from PC power supplies.
I don't know why the transformer is running so much
cooler after removing the AC grounding of the primary
center. I don't think there was enough energy in those
transients to account for the heat.
Well, I'm learning quite a lot here and have a working PA
and a coherent BPSK signal on-air, so I'm very pleased and
appreciate all the advice.
Another question for PA experts. In MOSFET power supplies
for Tesla coils, it is standard practice to block the body
diode of the FET using a Schottky diode in series with
the drain and use an external fast recovery diode to carry
any freewheeling current. This is because the body diodes
have a terribly slow reverse recovery. I was wondering
if this same reasoning carries over to LF/MF PA design,
which covers similar frequency range. The power levels
in TCs tend to be a lot higher though, perhaps that's
the difference.
--
Paul Nicholson
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