TopBand: Proximity to Trees

[W8JITom@aol.com]

In a message dated 96-12-13 22:05:31 EST, you write:

>

It seems to me a tree would be a useless antenna.

I've never observed trees to affect FS readings except at VHF and microwave.
The attenuation is greater as frequency increases. Roy Lewallen W7EL said he
thinks a very thick pine forest attenuated his 40 meter signal several dB
over a long groundwave path, but he wasn't positive. 

Nichrome or stainless steel is poor as a dipole, nichrome has about 37 times
less conductivity than copper.

If I soak a rope in salt water it is useless as an antenna, it has about 1000
times less conductivity than copper.

Sap is much worse than saltwater, it has a fraction of the conductivity of
saltwater.

Common sense and experience tells us that that trees don't affect 1.8 MHz
signals much at all. As for the bamboo, how do quad uses get away with using
bamboo spreaders if bamboo is so conductive? In a quad, the bamboo is at
right angles to the element and in some designs attaches right to the voltage
points.

If I replaced the bamboo with a string of resistors, the effect would be
almost NIL if the resistors paralleled the radiator.  If I attached them at
right angles at the voltage point, the effect would be greatest. Something
else was wrong in the groundplane.

If trees are as bad as implied, many many 160 operators and BCB stations
would be in severe trouble. You can bet the ranch there would be a lot of
data publised, and BC stations would select sites without trees in the path
to the service area. The only time this is a documented consideration is at
VHF and higher.

>Much of the above is modeled on higher levels of NEC that are not
>released to the public. 

What is the special NEC program used for trees, Elm-nec??

73 Tom

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