Slight correction, Gene.
The LPDA is at LEAST a two-element radiator. On some frequencies [at
or near the mid-point of its design] it will approximate a
three-element beam.
This is because at least one of the longer elements will act like a
reflector, while one of the shorter elements will act like a director.
Dr. Duhamel's work at Collins did NOT go unnoticed by this geezer.
73
Don
N8DE
Quoting Gene Smar <ersmar@verizon.net>:
> Jim:
>
> FWIW - A LPDA is at best a two element radiator. The gain will
> likely be less than that of a three element Yagi. The LPDA
> provides a wider bandwidth than the Yagi, hence its popularity with
> military, embassy, etc. installations.
>
>
> 73 de
> Gene Smar AD3F
>
>
> From: jim Jarvis <jimjarvis@optonline.net>
> Date: 2008/07/14 Mon PM 01:41:10 EDT
> To: towertalk@contesting.com
> Subject: [TowerTalk] C3 value?
>
> TT:
>
> I just picked up a 12 year old Force 12 C3, in an estate/takedown
> situation.
> At the same time, I had two guys approach me, to buy it from me.
>
> At the moment, I'm undecided whether to put this up, or to put up my
> T8 lpda,
> for general purpose use, and light-duty contesting.
>
> Other than rusted uBolts which hold the elements on, the antenna is
> clean and
> in good shape. This is the 3 element version, which I take to be
> the original C3.
> It uses F12's single feedline, direct connected for 20m, and
> capacitively coupled for 10 and 15m.
> I guestimated a 16' boom length. We were all too tired to measure
> it, after the
> takedown.
>
> So, I have a couple of questions:
>
> 1) What's a fair market value for the antenna?
>
> 2) Does anyone have first hand experience with it, on 12 and 17m?
> F12 says it works there.
>
> 3) Does anyone have first hand experience of performance vs. an lpda?
>
> I have some thoughts on item 3. That is, the Tennadyne logs
> outperform trapped 3 el. tribanders,
> due to their efficiency. The F12 antenna, however, is three
> monobanders on a common boom.
> No traps. So, I would expect the C3 to slighty outperform the log,
> on three bands, stipulating that f/b, gain,
> and vswr curves may not align to actually produce the hoped for best-
> cast performance.
>
> Your thoughts?
>
> n2ea
>
>
>
>
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