[TowerTalk] 43 foot vertical feed

[K4SAV]

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 at marietta.edu
>
>
>
>