[NLRS] Is there published data on tree foliage ...

[wb7dru at usfamily.net]

In my research of historical IEEE published studies last night I found that the typical loss due to foliage at UHF was about 10 db (Dr.C.Y. Lee).  This correlates to what I have seen working in RF system design in the twin cities.  There was one case a few years ago when I found a 20 db loss in the Minnesota river valley near Chaska.  In addition, the amount of moisture in the leaf does effect the attenuation.  I have seen coverage areas that worked during dryer summers but summers with more moisture (and less then this one)  sees a reduction in coverage.

My two bit empirical comments.

Dave

David Donaldson
WB7DRU/NNN0AXK
Burnsville, MN
EN34ij
Sent from my android device.

-----Original Message-----
From: Jon Platt via NLRS <nlrs at mailman.qth.net>
To: nlrs at mailman.qth.net
Sent: Fri, 11 Jul 2014 8:00 AM
Subject: Re: [NLRS] Is there published data on tree foliage ...




Another source of interest is ITU-R P.833-5 titled Attenuation In Vegetation.   The paper does include a table that shows "attenuation through woodlands" in dB/m vs frequency.   In their work they found a different attenuation rate for vertical vs horizontal polarization below 1 GHz stating that this was perhaps due to trees trunk. 

Here are some eyeballed values off the table.

Freq            -----  dB/m ------
  50            0.01 (H)    0.03 (V)
144            0.03 (H)    0.06 (V)
432            0.09 (H)    0.15 (V)
1 GHz          0.2
10 GHz        2
24 GHz        5

No comments on wet vs dry but they do say these are ball park numbers that vary significantly based on the type of trees and whether they are leafed out or bare.   Also they talk about increased attenuation when they are moving due to wind  ..... foliage movement increases attenuation.

73, Jon
W0ZQ

 
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