An EZNEC model of your antenna (height of 35') shows it to be resonant at
1865 kHz. The minimum SWR was adjusted to 2:1 by adding GND loss of 8 ohms.
SWR is all you need to tune the antenna. Is minimum SWR at 1977 kHz?
I would add more wire and tune the length for minimum SWR at your frequency
of interest. While doing that feedpoint shunt inductor (about 4uH is a
start) can be added to achieve a 1:1 SWR. That does not improve the SWR
bandwidth though and as I like to roam about the bottom 100kHz in contests
I don't bother. The antenna tuner takes care of that.
Dave
On Thu, Mar 25, 2021 at 5:07 AM N4ZR <n4zr@comcast.net> wrote:
> I have been trying to replace my inverted L, which broke a few weeks
> ago, and am having all sorts of puzzlements. Please be kind - I was a
> history major.
>
> 1. The inverted L broke at the turn, so I went looking for sturdier
> wire. I wound up with some #14 insulated recommended by our local RF
> maven, and put up 140 feet initially, figuring I would prune it *up*
> into the CW part of the band. Imagine my surprise when it showed up
> resonating at 1977 KHz (on an AA-55 Zoom). Does insulation have such a
> profound effect on velocity factor?
>
> 2. My feedpoint arrangement has 17 turns of RG-400 as a common mode
> choke, with the radial field connected to the RG-400 shield at the
> antenna end. Initially I tried measuring the resonance without the
> radial connection. No resonance and infinite SWR. I connected the
> radial field (8 X 70-foot radials on the ground) and that's when I saw
> the 1977 KHz resonance (X crossing zero). SWR at minimum was above
> 2:1. Does this make sense? I know the radial field is inadequate for
> good performance, but...
>
> --
> 73, Pete N4ZR
> Check out the new Reverse Beacon Network
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>
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