Hi Martin,
unfortunately you can't test at 10ft and tune the driven element only.
Neither adjusting SWR is the proper way to obtain reasonable F/B, BW
and gain.
Even tilting upward the antenna isn't a solution since you'll detune
the reflector if the distance from ground of it is not enough.
In a 2 element yagi none of the element is self resonant within the
band.
I did a light modeling of something like that, imposing a full band
coferage and a direct feed.
It comes out a reflector of 11.7ft and a driven of 11.0Ft.
The spacing is 7Ft.
73,
Mauri I4JMY
2el Beam
over ground
21.250 MHz
2 wires, feet
h = 40
d = 11.0084
r = 11.69124
s = -7
1 0 -d h 0 d h #12
1 s -r h s r h #12
1 source
wire 1, center
---------- Initial Header -----------
>From : towertalk-admin@contesting.com
To : "towertalk@contesting.com" <towertalk@contesting.com>
Cc :
Date : Wed, 06 Nov 2002 19:41:18 -0600
Subject : Re: [Towertalk] Freq on Ground and On Tower
> I should have mentioned that it is a two element wire beam using bambo
o to
> support the 12 gauge stranded wire. I will tilt it and measure again.
I
> am feeding directly with RG 213 with a .20 spacing.
>
> Tom W8JWN
>
> Tom Martin wrote:
>
> > I built a 15 meter beam with the DE cut for 21.250. The MFJ analyze
r
> > reads 23.000 for a 1-
1 match. I added about 8 inches and the best SWR
> > is at 22.500. These tests were made at 10 feet. Will the frequency
go
> > down when the beam is at 40 feet? I can't believe that I have to ke
ep
> > adding to the DE.
> >
> > Tom W8JWN
> >
> > _______________________________________________
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__________________
> AN Wireless Self Supporting Towers at discounted prices,
> See http://www.mscomputer.com
>
> Wireless Weather Stations now $349.95. Call Toll Free,
> 888-333-9041 for additional information.
> _______________________________________________
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