Varying Antenna Height was: Re: [TowerTalk] SteppIR 4 Element Yagi - Analysis and Thoughts

[Bernard]

    Thanks to all who replied on this thread.  There were a lot of good
comments and I am going to print the answers for future reference.

    I did get my copy of QST today and that MonstIR antenna is some array!
It is, however, too much antenna for my tower system.

    I tried to call Fluid Motion a couple of times today, but all I could
raise was their voice mail system.  I didn't leave a message because I
wanted to talk to someone about the possibility of a 40-20 M driven element
(only) on the 3 element SteppIR array.  Maybe I'll try again tomorrow.

    By the way, is Dayton this weekend?  If so, maybe they are gone for the
week.

        73


        Bernard, WA4OEJ
----- Original Message ----- 
From: "Pete Smith" <n4zr at contesting.com>
To: <towertalk at contesting.com>
Sent: Wednesday, April 14, 2004 7:32 AM
Subject: Varying Antenna Height was: Re: [TowerTalk] SteppIR 4 Element
Yagi - Analysis and Thoughts


> At 08:13 AM 4/14/04, Bernard wrote:
> >         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.
>
>
> The program HFTA, bundled with the current edition of the ARRL Antenna
> Book, displays statistics for arrival angles derived from thousands of
> IONCAP runs modeling propagation over an entire sunspot cycle on all HF
> bands.  It also calculates a figure of merit for each antenna system
> evaluated, which is based on how well the antenna system's pattern matches
> the distribution of arrival angles (I explained out this idea, then called
> "scoring," in a National Contest Journal article about 4 years ago).
>
> Going from this theoretical construct to an operationally useful matching
> of antenna height to arrival angles is tricky.  During a single day's
> opening on 20, for example, arrival angles may vary by as much as 2 or
> 3:1.  You would find yourself cranking the antenna up and down at least
> twice per opening, as angles went from relatively low at the start and end
> of the opening to relatively high in the middle of it.  There would also
be
> significant angle variations depending on which part of a continent you
> wished to work.  For example, the optimum antenna height for working UAs
at
> 1400Z could be a lot different than that required to work G's.  And of
> course, the "right" height for 20 is probably very different from the
> "right" height on 10.
>
> I suspect that on balance you are better off fixing the height of your
> antenna where it gives the best compromise match to arrival angles on your
> bands of interest, wherever that height is, and then adding other antennas
> to deal with other special needs, even if they are just wire dipoles.
>
> Just my two cents.
>
> 73, Pete N4ZR
> The World HF Contest Station Database
> is back, at www.pvrc.org/WCSD/WCSDsearch.htm
>
> _______________________________________________
>
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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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