Two comments :
Back in the mid 90's W1KW stacked two fairly large LP's. From what I
observed, including a contact wtih him while I was visiting TU2AA, It did
very well - top of the pile ! Also, as you may recall there used to be
stacked, tilted LP's for TV reception. Of course they would have been many
wavelengths high.
I'm a relative newcommer so it may have been previously discussed in
detail, but what about the TH-11. Back when Hy-Gain was really Hy-Gain I
talked with the guy who designed that and was quite impressed, but I haven't
heard much about it's success or failure electrically or mechanically.
Gene / W2LU
----- Original Message -----
From: "jim Jarvis" <jimjarvis@optonline.net>
To: <towertalk@contesting.com>
Sent: Friday, January 22, 2010 4:19 PM
Subject: Re: [TowerTalk] LP vs SteppIR
>
> I made comments directly to Doug, at his first posting, and said that this
> thread would
> again get legs. :)
>
> So let me repeat some of my comment, for those who didn't see it the last
> time.
>
> 1) I've had several LPDA's, the T8 being the best of them. It's head
> and shoulders
> above most trapped tribanders on short booms. The F12 C3S may be an
> exception,
> It's pretty good.
>
> 2) I changed from LPDA to a 3 el SteppIR, and was extremely pleased with
> its performance.
> It was a 3 el, and sure enough, results were like going from a 2 el yagi
> with the lpda
> to a 3 el with the steppIR. No magic there.
>
> Band change, with the Icom interface, was very fast. It took
> approximately
> 2-3 seconds for the computer to command the rig, amp, and antenna to
> switch over.
> Barely enough time to get a sip of coffee, before calling the station I
> was chasing.
> (I like to use the bandmap in small station contesting, in a point &
> click mode.)
>
> 3) Stacking Log Periodics:
>
> An interesting topic. And one which seems worth experimenting, to me.
> I started to, but got wrapped around the axle:
>
> With two T8's, each with 16' booms, you can put the front elements half
> wave apart
> at 28MHz, and the rear elements half wave apart at 14 MHz. The upper
> antenna
> tilts downward and the lower antenna tilts upward. I don't recall the
> angle, at this point,
> something like 22.5 degrees. My plan was to mount the lower antenna with
> the longest
> 20m element at 36', and the upper 20m reflector at 70'.
>
> I went so far as to buy two blank mast-boom plates from Tennadyne, and
> have them
> locally drilled for the calculated tilt angles. I was in process of
> designing the In/Out of
> phase system, which can be done fairly simply with a single relay, given
> the transmission line boom
> feed system for the T8.
>
> Somewhere in there, I got bogged down trying to model the thing. Cebik
> also got
> bogged down modelling it. Healthy discussion followed. I was about to
> buy the second
> LPDA and get on with my empirical approach, when a hurricane blew
> through, took out
> a big oak tree, which took out my tower. Then I got transferred.
>
> The feeling was that tilting the antennas would tend to raise the
> radiation angle, at the
> heights we were talking about. If I could have put the lower one at 70'
> and the upper
> at 100, it might have been different. That's what we had hoped to model.
>
> I still think this would be a worthy experiment--but not one I can pursue
> in suburbia.
>
> N2EA
>
>
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