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[TowerTalk] 20m / 5 el vs 4 el 1/2 wave boom

Subject: [TowerTalk] 20m / 5 el vs 4 el 1/2 wave boom
From: Bill Tippett <>
Date: Tue, 30 Aug 2005 06:58:03 -0400
List-post: <>
KT2Q wrote:
 >It's either the Force12 5 element or the M2 4 element 20M4DX.
Both have 1/2 wave booms - 36ft.

         Tony, the best way to answer your question is
to see full curves for Gain, F/R and SWR for both
antennas...i.e. modeling.  However, if you don't have
those, here's my guess based on looking at a lot of
optimized 5 element designs on 10 meters.

1.  1/2 wavelength is very short for a 5 element.
2.  3/4 wavelength is about optimum for a 5 element.
3.  The above assumes traditional designs, not a
dual-driven cell (like KLM) or the OWA trick of a
very close spaced first director.  If that is done,
then the 5th element might buy some SWR bandwidth,
but probably not much in Gain or F/R.  I'm not
familiar with the Force12 and can't find a picture
of it on their website, but my guess is they are
using an OWA design or variant.
4.  I would probably go with the 4 element for
reasons of cost, wind loading and weight without
any more info than you have given.

         Have you asked both manufacturers for full
Gain, F/R and SWR bandwidth curves?  Surely they
have them since both Force12 and M2 use modeling.
They might forward them to help in your decision.

                                         73, Bill  W4ZV 


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