Angel Vilaseca wrote:
It is interesting to see that lots of literature have been written about
the plate choke and almost none about the output choke. Both chokes are
in a circuit with high currents and voltages. Both are wired between a
high RF point and RF ground. It seems that the worst problem with the
plate choke - resonance - is simply not an issue with the output choke.
Why?
The 'output choke' is not exposed to high RF voltage. A legal limit amp
operating into a 50-ohm load with a reasonable SWR will have less than 500v at
this point. And there is no DC current normally flowing in this choke. It's a
very lightly-stressed component (unless the blocking cap fails).
Series resonances are problematic because they show a very low impedance. But
'low' is relative. In the 50 ohm part of the circuit, a much lower impedance
can be tolerated. So although a series resonance right smack in a ham band
would be undesirable, you wouldn't have to be very far off of the resonant
frequency to have a high enough impedance that it could be ignored.
I don't see any reason to not use a toroid.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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