On Thu, 6 Sep 2001 17:35:28 -0400 "David L. Thompson"
> Any software is just a tool. At the best case the software tells
> you what
> to expect. At worst case the software at least tells you if its
> worth the
> effort. The problem is interaction with other nearby antennas. I
> had a
> perfect looking W2PV 24Mhz 3el that fell apart within 7 feet of the
> K6STI had an interacion model that showed promise. You need both
> there is nothing on the tower or nearby (40 feet or so).
There's a pretty easy test for interaction on yagi antennas, once
they are installed.
The yagi characteristic most sensitive to interaction is f/b ratio.
f/b deteriorates much more than forward gain, and, fortunately,
f/b ratio is fairly easy to measure:
1. Have a ham across town transmit a steady signal.
2. Turn the back of your antenna toward him, and note the s-meter
3. Turn your antenna toward him and crank in attenuators until the
s-meter matches the original reading.
4.Read the f/b ratio off the attenuator setting.
A precision attenuator is nice, but even the attenuators/AIP built
into modern radios are fairly accurate.
Dave Hachadorian, K6LL
Big Bear Lake, CA
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