[Towertalk] Stackspacing for Triband Beams

[Guy Olinger, K2AV]

Stacking of dissimilar tribanders is problematic. Your 30 foot spacing
should be left alone.

Practical considerations around guy wires will govern where the
antennas go. Unless all guys are Phillystran, having guy wires run
through one of the antennas in order to match some theoretical
distance to the nearest inch will not produce wanted results.

Triband antennas vary in the difference between feed phase and release
phase of the driven cell/element, per band. They also vary in the
effective position of the driven cell/element, per band. These are
equal for identical tribanders, where equal feedline distances to the
pair from the selector box are effective. For all else it's an art
form. Lacking phase measuring equipment and a portable reference
signal transmitter, you make your guess and you live with it.

NEC-4 runs on stacked C31XR's show that distances in excess of 35 feet
produce large unwanted lobes first on 10 and then on 15. Stated
differently, the optimum distance for 20 meters cannot be used without
undesirable results on 10 and 15.

Although 28-33 is not optimum for 20, remember that stacked tribanders
are ALWAYS a COMPROMISE. Anything around thirty that fits the guy
wires will work OK.

AND MORE THAN ANYTHING, always remember that the greatest db
advantages are to be found between the ears, in the guise of operating
skills. Stated differently, a lid braying ineffectively at a pileup,
ramped up with an amp and a big antenna, is still a lid braying
ineffectively at a pileup. A top op with the same amp and a big
antenna is the fella that likely beats you in the next dx test.

73, Guy.


----- Original Message -----
From: "Dale L Martin" <kg5u@hal-pc.org>
To: "TowerTalk Reflector" <towertalk@contesting.com>
Sent: Saturday, November 30, 2002 10:38 AM
Subject: [Towertalk] Stackspacing for Triband Beams


>
>
> I've looked through the archives and cannot find the thread
discussing
> recommended spacing of triband beams on a tower.
>
> I've got an A3 hardmounted at 40 feet with a C3 at 70 feet.
>
> Should the spacing be a 1/4-wave at the lowest frequency?
>
> 73,
> dale, kg5u
>
> _______________________________________________
> AN Wireless Self Supporting Towers at discounted prices,
> See http://www.mscomputer.com
>
> Wireless Weather Stations now $349.95. Call Toll Free,
> 888-333-9041 for additional information.
> _______________________________________________
> Towertalk mailing list
> Towertalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>