Hi Phil,
I don't know what the manual says about the mounting height yet.
I don't have it yet. In fact, it may end up being a home brew
model. But the Tennadyne T12 is looking pretty good right now.
What I _do_ know comes from measuring a number of LPDAs in
various environments to determine what their sensitivities are.
The LPDA is a driven array. This gives it some characteristics
which are significantly different from parasitic arrays. One of
these is _much_ greater tolerance to being operated at a
"cluttered" site. The site this one is going into is actually
very clean. The earth and the other antenna are really the only
nearby objects. The 40 foot height above ground is beyond 1/2
wavelength for the lowest frequency of operation. So there won't
be significant near-field zone ground losses. I'm not really
concerned about the LPDA maintaining its pattern a that height.
Once it is up, I'll be verifying the F/B. If it doesn't fly,
I'll post a warning here.
73, Eric N7CL
>From: "Phil Clements" <philk5pc@tyler.net>
To: <towertalk@contesting.com>
>Date: Thu, 21 Oct 1999 19:48:26 -0500
>
>> I live on a 192 foot AARZT hilltop with broad, relatively flat
>> river (wash) valleys extending out 5 to 8 miles in the
>> important directions. I'm putting up a 70 foot tower. At the
>> top will be a full sized three element 40 interlaced with a
>> full sized three element 30 on 40 foot boom (2 feedlines). At
>> the 40 foot level on a tic ring rotator will be a 12 element
>> LPDA coverng 14 to 30 MHz (30 foot boom, one feedline).
>
>Does the LPDA manual give a minimum height above ground to get
>the published specs? Looks to me like 20 and 17 meters will be
>influenced by the nearness to the ground.
>
>(((73)))
>Phil, K5PC
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