A great discussion has been taking place on eham regarding 43' verticals.
http://www.eham.net/forums/Elmers/201882
73,
Jim N9WW
James E. Chaggaris
President
PowerOne Corp.
1020 Cedar Ave.
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-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Pete Smith
Sent: Thursday, November 20, 2008 10:21 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 43ft Vertical Feeding Question and Balun type
You clearly need a tuner at the base of such an antenna, rather than in the
shack, but there are a number of possible choices for that service now. A
more interesting question is what the radiation pattern will look like on
the various bands. I ran a quick-and-dirty, and it appears that the optimum
(highest-gain) takeoff angle varies from 26 to 16 degrees on 80-20, then 37
and 57 on 15 and 10. That obviously makes a big difference in the
subjective reports on the various bands, depending on the distance.
There was a series of articles in National Contest Journal a few years ago,
using NEC-4 to evaluate on-the-ground/buried radials. The message I took
away from that series was "Them as has, gets." That is, at a QTH with very
good ground conductivity, the improvement afforded by many radials is
relatively small. At a QTH with poor ground conductivity, even a full-up AM
broadcast radial field will only get you somewhere close to the station with
very good ground and a few radials.
My 2 cents.
73, Pete N4ZR
At 10:55 AM 11/20/2008, Rick Stealey wrote:
>Michael,
>It would sure seem to me that a 43 ft vertical is essentially a random
>length antenna.
>I saw the web site too where they offer a balun to go with it. "It
>tunes all bands"
>they say, WITH YOUR TUNER in the shack, or at the base of the antenna !!!
>I did a quick and dirty check with 4NEC and got 122-j466 at the base on
>20 meters, an swr of 38:1 ! A sweep shows an SWR of >9:1 from 7 to 15
>MHz.
>On 40 m you get 150+j210, an swr of 9:1 On 80 you get 17-j257, an swr
>of 79:1 !!
>So it would seem to me you have a lot of work to do to match this thing
>at the base.
>It would not be a good idea to run coax straight into the house with a
>79:1 SWR
>and hope a tuner will fix things.
>I know there is a guy in Chicago on 20 meters running one of them with
>no radials who comes into NJ 20 over 9 at times and claims no knowledge
>as to how he does it.
>Guys he talks to rave about his rock crushing signal. Wouldn't it be
>interesting to compare his signal in real time with his neighbor
>running a beam, or a quarter wave vertical. I mean.... the laws of
>physics haven't been rewritten lately have they, and I missed out on
>it?
>Rick K2XT
>
>
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