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Re: tree polarization (was Re: Antenna Selection)



Would it help you guys if I told you that the hill that I live on has
something about it (I don't know what) that makes it ideal to transmit or
receive from?  Examples:

    1.  I can (from outside or inside the house) hit repeaters that are 30
miles away using an HT and 5W.

    2.  I use an RCA DSS dish (18") that "shoots" through the trees
(something that RCA said couldn't be done) and consistently read 93 or
better on a strength meter included with the system software that has a
scale of 0 to 100.  RCA says that most people only get 85 or so with or
without trees.

Maybe it's the hill, maybe it's luck, I don't know.  I *do* know that the
same types of pine trees that are here at my QTH will greatly attenuate a
VHF repeater signal, but it doesn't happen here.  Any suggestions as to why
this happens?  Theories and WAG's are welcome. :-)

Thanks.

Joel B. Black
jbblack@wwisp.com
-----Original Message-----
From: Franklin Antonio <antonio@qualcomm.com>
To: Richard@g3rwl.demon.co.uk <Richard@g3rwl.demon.co.uk>
Cc: amsat-bb@AMSAT.Org <amsat-bb@AMSAT.Org>
Date: Saturday, September 26, 1998 6:00 AM
Subject: [amsat-bb] tree polarization (was Re: Antenna Selection)


>Richard:
>>>>Trees absorb *vertical* polarisation better than any other.
>Franklin:
>>> I am really surprised by that statement.
>>> Can you provide a reference to the technical literature\
>Richard:
>>No. Saw it in RSGB's "Radio Communication" several years ago. Might have
>>been in the same issue that talked about using trees as vertical radiators
>>for hf
>
>Franklin:
>I can believe it for HF.  At HF freqs, you need long pieces of tree to be
>resonant.  For most kinds of tree, that means the trunk, and trunks are
>indeed mostly vertical.  At higher frequencies, smaller branches, or even
>leaves or needles are more likely to be the parts that matter, and they
>tend (for most kinds of trees) to have a more random orientation.
>Therefore, I'd be very surprised if signal attenuation due to trees was
>very polarization specific at VHF or UHF or higher.
>
>
>
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