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

[Rolf Krogstad]

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
>
>