Vic has it right. Short the choke and use a grid dip meter to find series
resonance. For best results the choke should be mounted in place and
connected to the tubes and tank. I have checked with a grid dip meter
without shorting the choke and found little difference in series resonance
when it is installed in the circuit.
Parallel resonance is NOT a problem. It is actually desired if the choke is
small in value. It is common practice in many amplifiers to operate the
choke in parallel resonance on 160 meters. Part of the plate tune capacitor
is used to resonate the choke.
> -----Original Message-----
> From: email@example.com [mailto:firstname.lastname@example.org] On
> Behalf Of Vic K2VCO
> Sent: Tuesday, October 13, 2009 11:53 AM
> To: Jim Tonne
> Cc: email@example.com
> Subject: Re: [Amps] Checking Plate Choke resonance
> Jim Tonne wrote:
> > Gents:
> > About this RF choke resonance thng . . .
> > Isn't there some rule about the choke being
> > open-circuited (no connections to it) and/or
> > shorted (piece of wire across it) when you
> > check for resonances?
> Using a GDO, you SHORT the choke to check for SERIES resonances.
> I don't see how a parallel resonance would hurt, since it would create a
> very high
> impedance, which is desirable.
> Vic, K2VCO
> Fresno CA
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