On Sat, 10 Oct 2009 11:24:48 -0400, "rich ferguson" <firstname.lastname@example.org> wrote:
>>> Does anyone know how to check A plate choke for resonances using a vector
>>> network analyzer (VNA).
>73's Rich N2XQM
Sweep the choke across the planned operating frequencies and watch for any drop
or rise in impedance at particular frequencies. As a general rule the impedance
of the choke should be about ten times the plate load impedance or more. When
you see a sharp rise to near-imfinite impedance you have a parallel resonance.
When you see a sharp drop to near-zero impedance you have a series resonance.
Neither resonance is harmful provided it is well outside the ham bands. All
chokes have resonances; the trick is to stay away from those frequencies.
73, Bill W6WRT
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