@>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
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: K7LXC@contesting.com
Sponsored by Akorn Access, Inc & KM9P
|