>
>I can tell you experience trumps theory on these things. I have had several
>antennas (tribanders and monobanders) mounted down the tower where they were
>pretty close to the EHS guy wires. SWR was always changed for the better
>when
>the EHS was replaced with Philly or Polyrod, sometimes significantly.
SWR doesn't tell you anything about pattern. It just happens to be easy to
measure, and unexplained changes in SWR tell you that something in the
antenna system has changed, so it's a very useful diagnostic tool.
A 3 dB pad in series with the feedline will dramatically improve the SWR
and the apparent bandwidth will also increase, but is probably not a
desirable strategy in general.
In your specific case, the change in SWR (presumably from the
manufacturer's data, or from free space adjustment) tells you that there's
some sort of interaction, and, in general, interactions are bad, but not
always.
Compare a dipole and a 5 element yagi with closely spaced elements. The
dipole will have an impedance of about 70 ohms, and so will present a much
better than the Yagi, which will might have a feed point impedance of 10-15
ohms (without the matching network). The Yagi's also narrower band, once
you've matched it, particularly if you use a reactive matching network (as
opposed to, say, a tapered transmission line or a broadband transformer).
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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