[TowerTalk] 43ft Vertical Feeding Question and Balun type

[Pete Smith]

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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