I run #12 stranded house wire, 240 feet m/l, using a 1:4 balun. Works 180m
through 10m with a MFJ 993 BRT tuner.
I run bare wire. Easy enough to make a wire stripper with some wood and a
heavy duty razor/knife blade.
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________________________________
From: TowerTalk <towertalk-bounces@contesting.com> on behalf of Edward McCann
via TowerTalk <towertalk@contesting.com>
Sent: Wednesday, September 21, 2022 12:46:30 AM
To: David Gilbert <ab7echo@gmail.com>
Cc: towertalk@contesting.com <towertalk@contesting.com>
Subject: Re: [TowerTalk] Need some actual Inv V lengths using 14ga THHN
Thanks for the observation.
I’ve not yet heard from anyone whether and how EZNEC incorporates its
modification mathematically to account for dielectric insulation, although I am
quite familiar with the math suggested by Richmond, Lee and Popovic. But that
was only through 1984 or so. The line has been dead since.
Maybe someone will run a couple EZENECs and determine Vf of insulated wire in a
meaningful manner.
The obvious return path is through the ground, not the dielectric, just as it
is the vertical, hat or no hat, with the theoretical ideal case being the
hard-to-find perfect ground into which the image can be realized. Of course, as
the bumper sticker says, stuff happens, and that perfect ground is unobtanium.
Thanks again for your interest and reply.
73
Ed McCann
AG6CX
> On Sep 20, 2022, at 7:06 PM, David Gilbert <ab7echo@gmail.com> wrote:
>
>
> There is indeed a "return path" for a single wire. The wire capacitively
> couples back upon itself, and the dielectric affects that capacitance. That
> may sound strange, but think of a capacitive hat loading at the top of a
> vertical or at the end of a dipole. The wire itself is just a different
> geometry and therefore has less effect, but it's the same principle.
>
> EZNEC+ is based upon NEC2 and simply allows more wire segments than some
> other versions. I can't say whether or not NEC2 handles dielectrics, or
> whether W7EL added a calculation on his own, but if you define a dielectric
> in EZNEC+ it will result in a shorter wire for the same effect as a bare
> wire. That at least fits the physics of the situation.
>
> Dave AB7E
>
>
>
>
>
> On 9/20/2022 6:36 PM, Edward McCann wrote:
>> I’ve been looking for several decades for a technical analysis of the Vf of
>> a single bare and insulated wire, hearing nothing but lore from just about
>> everywhere, unbelievable proposals and formulas from some, exhortations from
>> academics that such a search is pissin’ in the wind, since there is no
>> return path, as there is in twin lead or in coax.
>>
>> 73
>> Ed McCann
>> AG6CX
>> Sausalito
>
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