Measured it with an swr analyzer. The dip in the swr curve , approximately
2.3:1, went from 14.1 mhz to 13.1 mhz.
On Mon, Jan 12, 2026 at 1:27 PM Ken WA8JXM <wa8jxm@gmail.com> wrote:
> How are you determining that the resonance shafted down?
>
> Ken WA8JXM
>
> On Mon, Jan 12, 2026 at 1:50 PM Tom Hellem <tom.hellem@gmail.com> wrote:
>
>> TT'ers:
>>
>> I made a choke to place at the feed point of a 20 meter vertical dipole.
>> 9 turns of #14 thhn wound on a 2.4" mix 31 ferrite toroid.
>> After I installed the choke, the resonant frequency appears to have
>> moved approx. 1 mhz lower.
>>
>> Is this the behavior I should be seeing?
>> I've used plenty of chokes on yagis, etc and never noticed this
>> before.
>>
>> Modeling in Eznec shows that changing the ground constants
>> does not appreciably change the resonance, so it seems that the fact the
>> ground getting wetter between the two measurements would not
>> be the cause.
>>
>> Any ideas?
>>
>> Tom
>> K0SN
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>
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