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Re: Trees and antennas and stuff



Where I first lived in upstate NY we lived in a valley and had to put our TV
ant on top of a hill. Had 500ft of foam 300ohm line coming down the hill.
one station was our local uhf ch 18 (494-500MHz). When it rained the signal
would drop to almost nothing but then if it froze, the signal came in like
gangbusters. after a rain I would open an upstairs window and give the line
a good shake that would oscillate up the hill ( had line suspended so I
could do that ) and as the water dropped off, up came the signal
dramatically.

Chris N2YQP
----- Original Message -----
From: "James H. Jipping" <jjipping@macatawa.org>
To: <amsat-bb@AMSAT.Org>
Sent: Sunday, July 14, 2002 7:22 AM
Subject: [amsat-bb] Trees and antennas and stuff


> Good Morning, everyone:
>
> I recall my days back at the University of Minnesota working with
> oscillators and using a Faraday Box.  As you recall  a Faraday Box is a
box
> that completely (or hoped to be ) confines any radiation inside. When Mode
> B first came about and the "new" 435 Mhz band was used I noticed that the
> trees which surround my house, when wet, were trying to be my own natural
> Faraday Box.  The effect can be very noticeable, even, a 435Mhz when the
> trees are dense and wet.  And, yes, the Tree Faraday Box gets better and
> better as the frequency increase.
>
> There are lots of interesting things going on.
>
> As the wavelength become a significantly small fraction of the openings in
> the screen used for a Faraday box  other things happen,  diffraction
begins
> to take place.  I doubt whether this has a chance of happening with trees
> as there are many, many layers of natural screens.
>
> I recall the difficulty radio astronomers have when the spacing between
> rain drops approximates the wavelength of the signal desired to be
> detected.  This is different than the Faraday Box, but what about the size
> of a wet leaf (hundreds of wet leaves) as compared to that wavelength of a
> 2.4 Ghz signal ???
>
> My front yard trees do not allow me to "see" through them for reception of
> AO-40.  As soon as AO-40 move in the clear I hear it again.
>
> Jim Jipping,  W8MRR
> AMSAT 5512.
>
> ----
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