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Re: satellite antennas



Hi Mal,
The "theory" of a + pattern being better for terrestrial (and EME) is fairly sound.  The reason is the difference in ground gain patterns for horizontal elements versus vertical elements.  If you model each half of the antenna separately, you will see the big difference in gain patterns--the horizontal elements have much more gain than the vertical elements.  This advantage for the horizontal elements is greatest at the zenith, but incrementally lost as the antenna is elevated from the horizon.  Keep in mind the + orientation will actually hurt you from predominantly vertically polarized signals, like most of the LEOs as they appear over the horizon.  

With all that said, if your antennas are primarily used for satellites, most people prefer the more consistant X pattern, which gives you half of the ground gain, but in a symetrical CP pattern.  The X pattern also has a smaller footprint in both axis (easier to avoid other antennas, wires, etc.).  This is of no small concern to me because I have to rotate my sat antennas between my HF dipoles and my chimney.
73,
Jerry, K5OE

In a message dated Mon, 12 Mar 2001  8:43:41 AM Eastern Standard Time, "Malcolm M. Preston" <np2l@worldnet.att.net> writes:

<< I've done it both ways and for satellite operation I can't detect any
difference.  I guess because of the circular polarization.  I decided to
keep it set +, my thought process being that this might be better for any
terrestrial use.  This theory is totally unproven.

Mal
NP2L@worldnet.att.net
----- Original Message -----
From: Larry <ve2me@AMSAT.Org>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, March 12, 2001 1:34 AM
Subject: [amsat-bb] satellite antennas


> I have a klm 2m14c and a klm 435-40cx.
>
> in both manuals it doesnt mention about how
> the elements should be positioned either
> in a + or x  cofiguration  when mounting
> the antennas on the crossboom.
>
> any suggestions?
>
> thanks -73
> Larry ve2me
>
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