At 08:35 AM 2007-11-02, Martin DM4iM wrote:
>Please see www.dl0wh.de and click on GOOGLE MAPS.
>The green arrow marks our lot. The dark green trees you can see
>determine the size of our lot. You see a narrow road running abt.
>315degrees <> 135degrees. Along the road there are 5 telephone poles, #1
>is at the west-corner of our lot, #5 is where the road bends north-east,
>distance abt 240 mtrs.
>We plan to use these poles as support for the beverage.
>
>The poles carry the telephone line.
>There is an electric fence parallel to the poles only abt. 1m away, 1m
>high.
>
>We will ask the farmer to switch the fence off for the contest.
>
>What can we expect from a , say, 200m long beverage on 80m & 160m (315deg)?
>Will the phoneline and/or the fence affect the performance?
I suspected that the presence of the parallel telephone line and the
electric fence would ruin the Beverage pattern, so I ran a few quick
models in EZNEC. A 200m Beverage (2m high) alone would have about 12
dB F/B and an RDF of 10.5 dB. I added 240m of telephone line (8m
high) and 240m of 1m high fence to the model and this reduced the F/B
to about 6 dB and the RDF to 9.5 dB. Despite the reduction in F/B,
this could be a useful receiving antenna with good rejection off the sides.
Often telephone cables are shielded and the shield is grounded
periodically, so I added a several grounds on the telephone line, but
the effect was no worse than noted above.
There are far too many variables to model this accurately (such as
signal pickup on the telephone line and fence where they bend in
other directions), so I suspect you will have to try it and see. Good luck!
73, Terry N6RY
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