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

[Donn, WA2VOI]

I think you made error in reading/writting, Rolf.  You show "432^.03," where it 
should be 432^0.3 !  Your math is correct for the value you used; with the 
"correct" value, the answer is ~1.1 meters, or about 42 inches.

Does that look better ?

As for what "foliage" means, the example that Bulletin 70 states is "...for a 
penetration of 10 meters (which is a single large tree, or two in tandem)..."

Helps ?

73 Donn
WA2VOI/0


----- Original Message ----- 
From: "Rolf Krogstad" <rolf.krogstad at gmail.com>
To: "Jon Platt" <w0zq at aol.com>
Cc: <nlrs at mailman.qth.net>
Sent: Friday, July 11, 2014 4:11 PM
Subject: Re: [NLRS] Is there published data on tree foliage ...


>
>
> This is interesting.  What is the mystery here to me is what is meant by
> foliage, or the variable R.
> If we assume, that Jon's numbers derive from Donn's formula, which may or
> may not be valid, we can calculate for R.  Let's use 432 MHz in the example:
>
> 432^.03 = approx. 1.2
> so .2 * 1.2 * R^0.6 = .09 db (from Jon's table)
> R^0.6 = .375
> R = approx. .195 meters
> .195 for us non-metric types is about 7.7 inches.
>
> This exercise has still left me confused.
> Does that mean the total width of the foliage if stacked and compressed is
> 7.7 inches?
> How does one apply that to real life?
>
> 73
> Rolf   NR0T
> EN34it
>
>
> ======================================================
> Donn, WA2VOI wrote:
>
> Foliage loss
> L(dB)= 0.2 * f^0.3 *R^0.6
> where: f = MHz
> R= depth of foliage (in meters)
> Valid for 200 - 95,000 MHz
> Depth of foliage R < 400m
> ======================================================
>
> On Fri, Jul 11, 2014 at 8:00 AM, Jon Platt via NLRS <nlrs at mailman.qth.net>
> wrote:
>
>>
>>
>>
>> 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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