[TowerTalk] Jungle forest attenuation

[Jim Lux]

At 12:54 AM 4/22/2006, Olivier F5MZN wrote:
>Thanks all for the informations. Unfortunately, I don't have access to
>the IEEE journals where most of the interesting papers looks to be on. I
>read some docs on the "Near Vertical Incidence Skywave", but this does
>not exactly anwer to my questions: my problem is rather to know what
>attenuation can I expect due to such a lossy ground as jungle forest,
>than incidences on the antenna itself.

If your antenna is above the forest, not a heck of a lot of loss. You 
"might" get a slight change in a pattern because of the refractive effects. 
You might try doing a NEC (or HFTA) model putting in soil parameters as
epsilon = 1.1 to 1.2  (instead of the usual 13 for "average" soil)
sigma = 1 to 0.01 mS/m  (instead of the usual 5 for "average" soil)
{these are the outer bounds suggested by Tamir in his first paper in 1967, 
based mostly on measurements by Parker and Hagn)
and see what happens.





>Anyway, thanks again and CU later!
>
>73
>--
>Olivier / f5mzn
>http://www.fy5ke.org
>
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