OK,
Now we know why its called "the radio art"...
Thanks for sharing that info Larry. Now for sure anyone thinking about
hanging a wire from a tree will most certainly have no reason not to do so!
73,
Dave
wa3gin
----- Original Message -----
From: "Larry Banks" <larryb.w1dyj@verizon.net>
To: <towertalk@contesting.com>
Sent: Thursday, December 29, 2011 8:11 PM
Subject: Re: [TowerTalk] trees and verticals
>I have been reading all of these posts and feel perhaps I can add to the
> conversation.
>
> Back in 2007 I was looking at property on the coast of Maine -- with tall
> trees. I was also curious about the effect, so I sent off a question to
> QST's "The Doctor Is In," not really expecting too much. I was very
> pleasantly surprised at the ensuing email "back-and-forth" between various
> people in Newington and me!
>
> Here is the response from Joel Hallas:
> ------------
> Larry,
>
> I haven't seen definitive words on the topic, however I believe trees have
> more of an effect for HF signals on vertically polarized signals then on
> horizontally polarized ones. Floyd Koontz, in his Horiz Ewe article in Dec
> 06 QST asserts that sap flow makes a difference and that if the sap drains
> in winter there is less of an effect on signals. This makes some sense,
> although I'm not sure why trees with wide branches wouldn't have similar
> effect on a horiz component.
>
>
> I am copying ARRL Antenna Book editor Dean Straw, N6BV, in case he has any
> thoughts,
>
>
> Regards, Joel
>
> Joel R. Hallas, W1ZR
> Technical Editor, QST
> American Radio Relay League
> ------------
>
> ...and the response from Dean Straw:
> ------------
> Hi, Guys:
>
> My understanding is that you'd have to put a vertical radiator very close
> to
> a tree for sap/no-sap to have any impact on the antenna's performance --
> perhaps within a foot of the trunk. Having said that, I know of several
> hams
> who did very well with "disguised, stealth" vertical wires run right up
> alongside the trunks of substantial pine trees. These gents worked lots of
> DX with such setups. Of course, YMMV!
>
> 73,
>
> Dean, N6BV
> Senior Assistant Technical Editor, ARRL
> Editor, The ARRL Antenna Book
> ------------
>
> ...and the response from Gene Zimmerman:
> ------------
> Hi Joel and Larry
>
> Everyone appears to have an opinion on this subject but definitive
> scientific works are more difficult to find - at least on the Internet.
> From
> a practical observational standpoint, I have found that low band verticals
> particularly 80 and 160 do not seem to be bothered by deciduous hardwood
> trees. However I used these during contests that occurred mainly in the
> colder months though I am reasonably sure that the sap has NOT drained by
> the end of October and I never noticed a difference between late October
> [leaves have turned but half of them are still ON the trees] and February
> [leaves gone and sap drained if it really does drain in MD].
>
> My station has all its yagi antennas mounted on a 24 ft mast beginning on
> top of an 83 ft tower on a 1/4 acre lot. The good news is that the tower
> sits at the edge of a group of hardwood trees so it is nearly invisible in
> spite of its size. The bad news is that the trees, once 70 ft tall are now
> approaching 90-100 ft range. I don't think the trees bother my HF
> tribander
> at 83 ft. Or my 7 el 6 meter beam at 87 ft. But the 2 meter beam at 95 ft
> may be impacted. I think my 2 m signal on moonrise/moonset EME is at least
> 3
> dB below what it should be. I also think that at 432 and above -especially
> above- trees are bad news [see below].
>
> The best reference I can give is section 2.3 [on p. 18] in a 1978 paper by
> A.G.Longley at the U.S. Dept. of Commerce.
>
> http://72.14.205.104/search?q=cache:IEqG7929jj4J:www.its.bldrdoc.gov/pub/ot/ot-78-144/complete_report.pdf+radio+wave+attenuation+trees+HF&hl=en&gl=us&ct=clnk&cd=22
>
> That paper and others that I have found agree that avoid trees entirely is
> the best course. Anything at 100 MHz and more is unacceptably attenuated
> by
> trees with non-deciduous pine trees being somewhat worse than deciduous
> hardwoods. At HF the effect may be quite a bit less noticable. Verticals
> at
> HF may be more affected but again the difference is only a very few dB
> more.
> Pine trees at HF are worse for the reasons you have already noted.
>
> Therefore I would say if you are moving to FN53 [please do so - it is the
> only grid on 2 meters within 500 miles I do not have after the advent of
> grid squares - my last contact with FN53 on 2 was in 1982 with W1BJ (SK)]
> you need to take the dense tree cover seriously. On 2 meters you will be
> impacted and above 2 meters unless you are clear of the trees you may be
> severely impacted. I suspect on 160 - 40 meters you won't have much
> trouble
> but a tribander buried in the trees is also likely to see some
> attenuation -
> maybe more than you'd be comfortable with. The same with 6 meters. For
> less
> dense trees I think the tribander and 6 meters would be o.k.
>
> Good luck.
>
> 73 Gene W3ZZ
> World Above 50 MHz
> FM19jd MD
> 50 => 10 GHz
> Grid Pirates Contest Group K8GP
> Member, CQWW Contest Advisory Group
>
> ------------
>
> If I remember, the URL for the paper may no longer be a good one,
> unfortunately. This link is the same paper:
> http://www.its.bldrdoc.gov/pub/ot/ot-78-144/ot-78-144.pdf
>
>
> The July 2008 QST "Doctor Is In" has the final response to my question.
>
> 73 -- Larry -- W1DYJ
>
>
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>
>
>
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