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Re: [TowerTalk] Verticals and trees (was Hustler 6-BTV installation )

To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Verticals and trees (was Hustler 6-BTV installation )
From: "Larry Banks" <larryb.w1dyj@verizon.net>
Date: Wed, 09 Apr 2014 21:38:49 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Hi Hans,

I asked QST's "The Doctor" this question a number of years ago. I have attached a series of emails I received from a number of well known hams below. This is the best I have ever seen. It is quite long

73 -- Larry -- W1DYJ



-----Original Message----- From: Hans Hammarquist
Sent: Wednesday, April 09, 2014 12:08
To: towertalk@contesting.com
Subject: [TowerTalk] Fwd: Hustler 6-BTV installation

Thank you, Gary,

I have always wondered how surrounding (vertical) trees are affecting the radiation from a vertically radiating antenna. There are (probably) as many opinions about this (or many be more) than there are (active) radio hams.

Best 73 de,
Hans - N2JFS


-------------------------------------------------------------------------------------

From: Eugene Zimmerman
Sent: Tuesday, January 02, 2007 18:33
To: Hallas, Joel W1ZR ; Larry Banks
Subject: Re: Dear Doctor: Antennas and Trees

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

-----------------------------------------

----- Original Message ----- From: Hallas, Joel W1ZR
To: Larry Banks
Cc: Zimmerman, Eugene W3ZZ
Sent: Tuesday, January 02, 2007 4:30 PM
Subject: RE: Dear Doctor: Antennas and Trees

I have known serious V/UHFers who had towers high enuf to clear the trees, so it may be a problem there. Perhaps Gene has some thoughts?

Regards, Joel

Joel R. Hallas, W1ZR
Technical Editor, QST
American Radio Relay League
The national association for AMATEUR RADIO
TuTh;  860-594-0393
MWF; 203-226-7353


--------------------------------------------------------------------------------

From: Larry Banks [mailto:larryb.w1dyj@verizon.net]
Sent: Tuesday, January 02, 2007 4:14 PM
To: Hallas, Joel W1ZR
Cc: _Larry@ home; Straw, Dean, N6BV
Subject: Re: Dear Doctor: Antennas and Trees


Thanks Joel,

Floyd's comments agree with KF4IX's comments in Nov. '91 QST. That makes sense to me. I would assume that horizontal branches would have to be really horizontal and ~¼ wave to have much effect -- probably more obvious on 10M and 20M than 80 & 40. Branches are also "usually" at about a 45º angle, more or less, which I think would decrease the effect by 20 dB or so.

My bigger concern is VHF and UHF -- one reason I am choosing this site is that it's in FN53, much rarer than my current FN42, and I love the VHF contests.

I do know that trees are BAD for SHF.

Thanks again & 73,
Larry
W1DYJ

------------------------------------------

----- Original Message -----
From: Dean Straw
Sent: Tuesday, January 02, 2007 15:33
To: Hallas, Joel W1ZR ; Larry Banks
Subject: RE: Dear Doctor: Antennas and Trees

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 and HNY,

Dean, N6BV
Senior Assistant Technical Editor, ARRL
Editor, The ARRL Antenna Book

-----------------------------------------------------

----- Original Message -----
From: Hallas, Joel W1ZR
To: Larry Banks
Cc: Straw, Dean, N6BV
Sent: Tuesday, January 02, 2007 3:24 PM
Subject: RE: Dear Doctor: Antennas and Trees


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
The national association for AMATEUR RADIO
TuTh;  860-594-0393
MWF; 203-226-7353


--------------------------------------------------------------------------------

From: Larry Banks [mailto:larryb.w1dyj@verizon.net]
Sent: Monday, January 01, 2007 10:10 PM
To: doctor
Cc: _Larry@ home
Subject: Dear Doctor: Antennas and Trees

Hi Doctor,

I have been "lucky" in that the two QTH's on which I have been active -- Southern Connecticut in the early 60's as K1VFX and a current QTH ten miles north of Boston -- have been on hills which have provided great upper HF and VHF antenna opportunities with simple roof towers. The lack of trees have meant poor horizontal antennas for 80 and 40 however. Now I am contemplating moving to Maine to a low coastal area full of tall Pines and hardwoods. I am wondering about the effect of trees on antennas.

Searching the ARRL site I found two references: a Nov. 1991 Technical Correspondence from KF4IX detailing the effect of HF verticals sited close to trees (not good) and a Dec. '85 Ham Radio article by Bill Orr, W6SAI, which I don't have since I gave my "all-but-Vol. 1, #1" set away to a library long ago (bad idea!) I also searched LB's web site, W4RNL, for info on trees and found nothing. A GOOGLE search on "antennas and trees" was also fairly useless -- about 1M citations, the early ones all about using trees for hanging antennas.

What is the effect on horizontal antennas -- dipoles, yagis, etc. -- that are on modest towers in a forest of tall pines and hardwoods? Is there a difference between winter and summer -- remember, this is Maine. Is there a difference between HF, VHF, and UHF?


73,
Larry
W1DYJ


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