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[TowerTalk] 1

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Subject: [TowerTalk] 1
From: (Tom Rauch)
Date: Sun, 8 Aug 1999 16:58:16 -0400
> On Sun, 8 Aug 1999 14:13:13 -0400, Tom Rauch wrote:
> > I'd wager there is NOT an abrupt change in 
> > anything at the tree level at HF, since even 144 MHz signals are 
> > barely affected.
> Can't speak for the HF side, but 144 sigs are very much attenuated with
> trees.  There is a tremendous change in signal levels between winter and
> summer when the vegetation is on the limbs.  

Attenuation and other effects vary with distance the wave travels 
through the media. In a stand of trees 500 feet thick, we measured 
almost three dB of extra attenuation on 144 MHz over the same 
path distance in winter. At 2 GHz, attenuation was so great we 
couldn't even measure the signal level from a 2500 watt ERP 
system at the other end during summer. On 1370 KHz, we couldn't 
tell any difference at all, summer or winter.

Comparing a signal that travels miles through trees on two meters 
is pointless at HF, because most of the pattern is formed within a 
several hundred feet.

73, Tom W8JI

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