[TowerTalk] Choke on feed point of dipole

[Steve Maki]

As a point of reference, I wound a feed point choke for a JK 20M yagi 
out of THHN and found the apparent resonance had shifted well below the 
band compared to the other JK 20's on site fed with otherwise identical 
baluns but made from RG400 coax. The antennas are all well up in the 
air  (lowest is 80'. We're using it as-is so far, but the SWR on phone 
is pretty bad.

I believe it's a thing.

-Steve K8LX

On 01/12/26 1:46 PM, Tom Hellem 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
> _______________________________________________
>