The other day, just for fun, I swept a bunch of ol' RF chokes -- solenoid
wound, pie wound, etc. All of them exhibited nasty resonances somewhere within
the HF spectrum.
I then wound a few experimental coils on some toroids and one on a type 43
core worked exceptionally well -- very flat response with no resonances
anywhere below 50 Mhz.
The only gotcha with this part is that in a real world application the DC
plate current would saturate the toroid, killing the mu & the uH's.
Now here's where this concept crosses over in the silly side...
The saturation problem could be overcome by running an out of phase DC
current, servoed by the plate I, through a 2nd winding on the core. This
second winding would need to be RF isolated with a choke of its own but, for a
single turn winding a 10uH (air core) choke would be sufficient. The required
single turn current would be on the order of 10-15 amps. Sounds bad but, no
real voltage is required -- 10 Amps at .1 volt is only a watt. In a fortunate
circumstance, this current might be obtained "free" in series from a DC heater
supply.
Searchin' around the all knowing internet only uncovered a similar scheme to
cancel the plate DC in an "audiophile" single ended output transformer.
Has anyone ever see this done?
73 & Good evening,
Marv WC6W
http://wc6w.50webs.com/
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