[TowerTalk] SteppIR 4 Element Yagi - Analysis and Thoughts

[Jim Lux]

----- Original Message -----
From: "Bernard" <wtrone at comcast.net>
To: "Joe Subich, K4IK" <k4ik at subich.com>; "'G.E. Tucker'"
<gtucker at bostoneng.com>; "'Dan Levin'" <djl at andlev.com>;
<towertalk at contesting.com>
Sent: Wednesday, April 14, 2004 5:13 AM
Subject: Re: [TowerTalk] SteppIR 4 Element Yagi - Analysis and Thoughts


>     Joe:
>
>         I was wondering if you or anyone else on this thread have
considered
> a single antenna (like a SteppIR) on a motorized tower where you could
raise
> and lower the tower to optimize to the angle of arrival.  I haven't seen
any
> comments on this subject and I don't know if there are any computer
programs
> that take propagation data, etc. and calculate the optimum height.  I know
> that many "big guns" spend $1000s for that extra dB or two, but many of us
> don't have the real-estate for multiple towers and/ or antenna stacks.
>
>         Comments, anyone?
HFTA, in the latest ARRL Antenna Book does some of this modeling. It
compares propagation predictions (take off angle probabilities) with
patterns calculated from  terrain models (specified as heights along a
radial from your antenna) and the use of one (or more) of a library of
canned antennas which span a reasonable variety of types.

I'm not real wild about the program ARRL provided for getting the radial
data from terrain databases (I prefer RadioMobile), but it does work.  HFTA
also only does horizontally polarized radiation and assumes "flat" earth
(well.. really more like 1 dimensional waves, with ripples only in the
direction of propagation).