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"Stacking" 40M dipole question

To: <towertalk@contesting.com>
Subject: "Stacking" 40M dipole question
From: alsopb@VANCE.NET (alsopb@VANCE.NET)
Date: Mon, 25 Nov 1996 16:59:20 -0500

@>Guys,

@>I'm interested in "stacking" a Cushcraft rotatable dipole (half their
@>40cd2) with my 4 element GEM 10-15-20 meter quad.  Stacking isn't
quite
@>correct.  I plan to mount it parallel to the boom and 1 foot above it.
@>The GEM quad boom is only 16' in length.

@>I did some calculations with K6STI's AO program to assess the
@>interaction.  There was absolutely no impact on the quad  with the
@>shortened dipole modeled as a solid 1" full length dipole.  (Didn't
know
@>how to model the lumped constants and capacity hat of the real
antenna)
@> This was not entirely unexpected.  Metal booms don't impact the
quad's
@>performance either.

@>Now for the key question.  Does the boom (and tower) impact the rotary
@>dipole.  Again I modeled the dipole, first in free space.   Then I
@>modeled it with the 16' boom and 75' tower (20" diameter).   There was
@>absolutely no impact again.

@>Now for what Cushcraft says.  I sent a note about possible interaction
@>to Cushcraft.  They say the presence of the boom will seriously detune
@>the rotary dipole and mount it at right angles to the boom.   This
@>arrangement , when modeled, is detrimental to the quad.

@>So I have contradictory information.  The antenna modeling program
@>contradicts Cushcraft's statement.

@>Any thoughts on who is right-- or do I flip a coin and actually try it
@>with both orientations and find out both are wrong?

@>73 de Brian/K3KO
Vance Net Inc
End Of Message 


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