[TowerTalk] Shunt Feed Capacitor for Tower

[Steve Daniel]

I have a large KLM log periodic that I plan to put up at 100 feet. It is
this tower that I currently use as a top loaded vertical for 160. I also had
concerned about arcing when I realized the elements of the log are insulated
from the boom. I called KLM's successor, M2 I believe, to ask if this was a
problem. The fellow I spoke with said that never in his time with KLM or M2
had there ever been a report of a problem such as this. He simply did not
think it was an issue. And remember, he wasn't selling me anything. This is
an older antenna that I already have on hand. Steve Daniel, NN4T.
----- Original Message -----
From: <n4kg@juno.com>
To: <TOWERTALK@contesting.com>
Cc: <force12@fix.net>
Sent: Friday, February 08, 2002 1:30 PM
Subject: Re: [TowerTalk] Shunt Feed Capacitor for Tower


>
> N4KG response below.
>
> On Fri, 08 Feb 2002  Pete Smith <n4zr@contesting.com> writes:
> >
> > At 11:34 AM 2/8/02 -0600, n4kg@juno.com wrote:
> > >
> > >Another solution to the high voltage problem at the
> > >insulated end elements of F12, KLM, and X7 / X9
> > >antennas would be to install a relay to short the
> > >center of the end elements to the boom when
> > >you want to use the tower as a vertical, leaving
> > >the relay OPEN when you use the beam.
> >
> > I'm a little leery of serendipitous resonances and unexpected
> > interaction
> > that could result if you short elements and boom together.  Wouldn't
> > it make better sense to connect a small inductor between the element
> > center and boom (thanks W8JI), such that it looks like a short at 160m
> but
> > an open at 40m and above?
> >
> > 73, Pete N4ZR
> >
>
> With only a 4 to 1 frequency ratio, I expect it may be a little hard
> to make even an 'ideal' choke that will look like a short at 1.8 MHz
> and an open at 7 MHz since X = 2 pi F L.  At 14 MHz, you have
> an 8 to 1 ratio to work with which is quite a bit better, as long as
> you be careful to keep the self resonant frequency of the choke
> above 28 MHz.
>
> I think my relay suggestion makes a better OPEN and SHUT case :-)
> for those who are concerned about boom currents when using the Yagi.
> I wonder what F12 has to say about just connecting the end elements
> to the boom to prevent arcing when using the tower as a 160M vertical?
>
> Tom  N4KG
>
>
>
>
>
>
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