K8RYU wrote: "A couple comments. First off, the thing can be tuned from
the shack with an "unbalanced openwire" feed, simply a wire carefully
insulated from earth with, ideally, a number of parallel wires under it
in or on the ground. Needless to say this will put a LOT of high
voltage where people and pets might get hurt, but it will work and will
not suffer the losses of a piece of RG-213."
An UNBALANCED open wire feeder will radiate badly, and could have much
more loss than a piece of RG213 depending on feeder length and frequency
because it is close to the ground. Did you ever hear of a folded
monopole antenna? It's just a quarter wavelength of unbalanced feeder,
feeding a short circuit.
Jerry, K4SAV
Ralph Matheny wrote:
> A couple comments. First off, the thing can be tuned from the shack with
> an "unbalanced openwire" feed, simply a wire carefully insulated from
> earth with, ideally, a number of parallel wires under it in or on the
> ground. Needless to say this will put a LOT of high voltage where people
> and pets might get hurt, but it will work and will not suffer the losses
> of a piece of RG-213.
> HOWEVER
>
> To run it on 160 and 80 seems require such a simple matching system that
> I fail to see why one would do much else. A coil to ground, the size of
> which will set the resonance of the vertical, with a tap on it which will
> allow you to select the "50-ohm" point will get you all that the antenna
> and ground that you have can do. You'd need to switch the coils and taps
> to change bands, and perhaps even within the bands, but that all seems
> very easy to do with little loss. The greatest problem will be dealing
> with switching if really high power is involved, wien one might expect
> 5-10KV on the base of the vertical.
>
> Why do they sell these things??? I don't know, but I bought one back in
> 1960 while in high school. Then...it was called a "Gotham Vertical" and
> I don't think I'll ever forget the "I've been had" feeling when the box
> was opened and my $19 purchase consisted of 23 feet of aluminum tube,
> 4 conduit clamps, and a piece of coil stock (not B & W). No magic box,
> no free lunch, no nothin' special. But...I sure did learn a lot from that
> vertical, and made a lot of contacts.
>
> Ralph Matheny
> K8RYU
> 207 Gibbons Place
> Marietta Ohio 45750
> mathenyr@marietta.edu
>
>
>
>
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