Matt T Powell wrote:
> I have been following the thread relating to the effects of steel
>guys affecting HF antenna patterns. I am wondering if the same effect
>occurs when using antennas from 50 mhz and above ? Has anyone using a
>rotating tower with VHF and UHF arrays pointing through the steel guying
>noticed any ill effects ? Or would it be worthwhile to invest in
>Phillystrand, to be used in the upper guys ?
>
You can expect high-order VHF resonances in normal lengths of guy wire,
considerable scattering causing pattern distortion, and some loss of
gain.
Obviously these effects will depend on the azimuth of the beam antennas
relative to the guy wires, and also on the beamwidth - in some
directions a UHF long yagi with a narrow beamwidth will not "see" the
guys at all.
As usual, the only way to be sure is to model the setup, in some detail.
This time, the capacitance of the egg insulators will definitely be
important ;-)
Even if you use insulating guys, the tower itself can be a significant
fraction of a wavelength wide at VHF.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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