[TowerTalk] Stacked tri-banders and 40m dipole - which antenn a where?

[Curtis, David B]

Hi Dave,
   OK, here is the "think-out-of-box" question of the day:

As you point out, putting a 40M dipole parallel to and spaced very
close to the boom of a tri-band yagi works pretty well.

So... why can't one build a 40M dipole and then use it *directly*
as the boom for a tri-bander?

Issues I can think of:
a. Tri-bander elements may provide a little capacitive loading
    that needs to be accounted for, but overall only serves to
    shorten the dipole.
b. Insulated gap at the center of the dipole might be a 
    mechanical weak point.  So... if a strong insulating material
    can't be found, perhaps the 40M dipole is gamma or T-matched.

Ok gang: so what is dumb about my suggestion?

73, Dave N6NZ
n6nz@contesting.com

-----Original Message-----
From: k6ll@juno.com [mailto:k6ll@juno.com]
Sent: Wednesday, August 11, 1999 10:13 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Stacked tri-banders and 40m dipole - which
antenna where?





On Tue, 10 Aug 1999 22:17:17 -0700 "Dan Levin" <djl@andlev.com> writes:
>
>My main antenna system will be a 2 stack of 4 element 20' boom 
>tri-banders,
>and a shorty forty rotatable dipole. 

Another option is to put the top tribander AND the 40 dipole
at 85', with the dipole parallel to the tribander boom. The
20' tribander boom shouldn't affect the dipole, especially if the
tribander elements are insulated from the boom. The dipole won't
affect the tribander, since it's at right angles. The dipole won't
directly add to
the windload, since it's at right angles to the tribander
elements, which is usually the worst-case wind direction for
a yagi. This option will also allow you to hang your lowband
wires from the mast at about 83 feet, using one of the
methods discussed here recently.

Since you are in California, 55' is a good height for your
lower antenna, and 30' is a good stacking distance for a
small tribander.


Dave Hachadorian, K6LL
San Diego, CA
K6LL@juno.com

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