[amsat-bb] Trees and antennas and stuff

["James H. Jipping" <jjipping@xxxxxxxxxxxx>]

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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