The plate choke resonances depends by its inductance and windings
capacitance, but stray capacitance also play a significant role. In
other words the same plate choke inside different amplifier can result
in different resonances likewise a different phisical positioning may
actually shift them in the same PA.
Expecially with the introduction of WARC bands, and with 160m coverage,
there isn't a single *perfect*, choke unless such choke is referred to
a peculiar amplifier and installation.
I check plate choke resonances using the spectrum analyzer and its
tracking generator connected to the output, with everything in place
(giving the proper load with a resistor across tubes and ground) and
tuning the PI on each band of interest.
By experience, switching a couple of chokes gives a net result between
1.5 and 30 Mhz while a single one with *parked* resonances is quite a
compromise and time consuming.
> ---------- Initial message -----------
> From : email@example.com
> To : "Bill Smith" <firstname.lastname@example.org>, <email@example.com>
> Cc :
> Date : Thu, 27 Sep 2001 22:33:55 -0500
> Subject : Re: [AMPS] Plate Choke test with MFJ-259B
> I assume you have the plug-in "Duckie" that converts
> your 259 into a GDO.
> The choke is tested in place, with a shorting strap across
> the two terminals. If the choke has over 150 uh or so of L,
> there may be two resonance's found between 10 and 40 mhz.
> The very popular choke sold by RF Parts and used in Ameritron
> amps is resonant around 11.5 mhz, and again between 10 and 6
> meters. That is why this choke is so desirable. It has sufficient L
> for 160 meters, and is good on the other 8 bands as well.
> Phil, K5PC
> Subject: [AMPS] Plate Choke test with MFJ-259B
> > What is the "correct" way to check a Plate Choke for
> > resonance with a MFJ-259B antenna analyzer? Do you
> > leave it in the amp or take it out, etc.?
> > 73,
> > Bill
> > =====
> > Bill Smith KO4NR
> > --
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