[TowerTalk] Data on attenuation by trees? reply de KØFF

[Bud Hippisley]

I just have to reply to two parts of this thread.  

1.)  Until I moved earlier this year my shunt-fed quarter-wave Rohn 25 160-meter vertical was buried in a heavily wooded plot at my old QTH.  The trees were a mix of deciduous and evergreen, and generally up to 90-100 feet in height, versus the 125-foot tower.  As measured by SWR variation in the shack or by ability to get out, I would have to say I saw no difference between wet trees and *dry* ones, although it seems to me the living ones are also "wet"  -- it's just that the moisture in *inside* the bark, rather than outside.  If the added moisture on the bark surfaces or the leaves had any effect, it was not obvious to me, and certainly far less than normal nightly fading and other propagation vagaries.  And no one ever accused my 160 vertical of not playing well.

2.)  During the past ten years or so of trying to improve my 160-meter receiving ability, I have come to the conclusion that, opposite to what my non-ham neighbors, relatives, and friends believed, the easiest antennas to keep up in the air are the ones highest up.  Beverages, at 6-10 feet in average HAAT, are the worst; they are virtually impossible to keep strung in a wooded area because Murphy's law requires that falling branches will seek out the nearest Beverage.  Even the parts of my Beverages that ran over lawn or meadow were at risk -- the neighbor's cows always managed to take out one or two each season.

Bud, K2KIR

>I, too, live in the woods now. (Luckily, I also live on top of a pretty good
>hill.)  It never really mattered much to me in any previous QTH, but I've
>always heard that RF absorption by deciduous trees varies from summer to
>winter, depending on the density and height of the surrounding forest, and
>the moisture content of the leaves. I have no idea how measurements that
>would account meaningfully for all the variables could be taken, but it's
>such an obvious question that somebody somewhere must have tried sometime. I
>would really like to see some data, if any exists. K3MGT
>
>----- Original Message -----
>From: K0FF <K0FF@ARRL.NET>
>To: <towertalk@contesting.com>; Wes Cosand <wz7i@ARRL.NET>
>Sent: Wednesday, November 22, 2000 8:15 AM
>Subject: [TowerTalk] Re: [TowerTalk] Data on attenuation by trees? reply de
>KØFF
>
>
> > Sorry Wes, I don't have the source of the info you require, but would like
> > to add that
> > as the resident of a dense forest, one of the most detrimental effects of
> > trees has
> > to do with Murphy's Third Law of Selective Gravitation, which states:
> > "A dropped or falling object will fall where it will de the most damage"



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