Based on my modeling experience (eznec) , getting the phasing right is a big
deal.
I recently stacked two 6m antennas. I modelled two indentical 5 element
antennas on 19' boom, vertically stacked with 16' between them. The gain
increased by about 2db over a single 5 element yagi.
Replacing the bottom by a 3 element totally spoiled the pattern. The launch
angle moved up considerably.
I next adjusted the antenna below so that the two driven elements were in
the same vertical plane (one exactly above the other). This fixed the launch
angle but the gain was only 0.5 db better than the 3 ELE LOWER antenna.
UGH!
I did not try other adjustments. It seems that it is really worthwhile to
consider phasing. After all, that is what produces the gain in the first
place.
Regards,
Rajiv, N2RD
----- Original Message -----
From: "J. Kincade" <w5kp@swbell.net>
To: <n4kg@juno.com>; <TOWERTALK@contesting.com>
Sent: Wednesday, October 17, 2001 2:56 PM
Subject: [TowerTalk] Stacking quandry
>
> I have a C3XL (33' boom) at 80' on a 45G. It works like absolute
gangbusters
> by itself (have yet to call anybody more than twice to get a comeback, and
> even twice is unusual), but naturally I'm greedy and want more, and would
> especially like more Africa in the log. After hunting for weeks, I've
about
> given up finding another used one just like it to stack at 40' or so (F12
> wants over $1300 + shipping to build me a new one - gulp). Have received
> dire warnings from several folks about trying to stack my C3XL with a
> dissimilar tribander below it (you'll never get the phase right, will
never
> work, bad idea, etc.) So I need to ask the audience, I guess: What's your
> take on a new C3 or C3S or something instead of a C3XL at the 40' level,
> using a Stackmatch and a swinging gate? Is this more hassle than it's
worth?
> Is it a phasing nightmare? I'm very reluctant to give up this great single
> antenna just to have two alike on the tower.
> 73, Jerry W5KP
>
> > With a 60 to 80 ft tower, I would go with two antennas,
> > one at 40 ft, the other on top. The bottom antenna could
> > be a simple trap dipole or 2L tribander with a bigger antenna
> > on top. The top antenna WILL have nulls in the ranges
> > supported by the ionosphere on 10 through 20M.
> >
>
>
>
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>
> -----
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>
>
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
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