[TowerTalk] How much do trees really affect verticals
Tom Osborne
w7why at frontier.com
Mon Aug 25 17:24:19 EDT 2014
I have 3 verticals in the woods next to my house. One is a 160 'L',
one is a vertical 40 meter dipole, and one is an 80 meter elevated
vertical with the base up about 6 feet.
They all seem to work just fine. ON 40 meters, I also have a delta
loop, and it is usually a toss-up which one is best. Different times of
the day different antennas work best.
We used to do our FD right on the beach, about 1/4 mile from the ocean.
We moved our site a couple of years ago to a park east of Coquille, OR.
This spot is in a little valley with 100 foot trees all around. We put
up our wire antennas in these trees and they didn't work very well at
all. We were surrounded on 3 sides by hills and after running HFTA, we
found the antennas were way to high and with the low take off angle,
most of the signal was going right into the hillsides. Next year we
lowered the antennas down to about 30 feet and it worked a lot better.
Sometimes other things can affect how good the antennas work. 73
Tom W7WHY
On 8/25/2014 10:49 AM, RLVZ--- via TowerTalk wrote:
> Hi Guys,
>
> FWIW, I will share an actual experience where a Ground Plane Vertical
> located in dense trees worked very poorly. One of my favorite Field Day
> antennas over the years has been a simple Hustler 5BTV vertical elevated 10-20'
> above ground level, and operated with 2 tuned radials per band. I've made
> thousands of FD Qso's on 40-10 meters with this arrangement and often get
> real nice pileups going. However, a few years back, my son-in-law asked me
> to do FD from his QTH in Central Illinois, which was surrounded by hundreds
> of trees. It was like operating from within a dense forest. The GP
> Vertical performed very poorly and operating was a miserable experience as I
> found it very difficult to makes Qso's, in fact it was more difficult to make
> Qso's than many of my QRP experiences. That said, my daughters cooking made
> up for it!
>
> My personal conclusion is that I love Verticals and won't be without one
> or more regardless how many Yagi's I have in the air. But now I'm a firm
> believer that they need to be located "in the clear". (just as many antenna
> books advise)
>
> 73, Dick- K9OM
>
>
>
>
>
> In a message dated 8/25/2014 8:55:39 A.M. Central Daylight Time,
> larryb.w1dyj at verizon.net writes:
>
> Hi Gregg,
>
> I asked this same question a couple of years ago -- of the QST's "The
> Doctor
> Is In." Here are the answers I received.
>
> 73 -- Larry -- W1DYJ
>
>
>
>
> ------------------------
> 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://www.its.bldrdoc.gov/pub/ot/ot-78-144/ot-78-144.pdf >
>
> 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 ... 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
>
> ----------------------------
> 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 [mailto:W1zr at arrl.org]
> Sent: Tuesday, January 02, 2007 12:24 PM
> To: Larry Banks
> Cc: Straw, Dean, N6BV
> 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
>
>
>
>
>
> -----Original Message-----
> From: k9kl
> Sent: Sunday, August 24, 2014 22:22
> To: TowerTalk at contesting.com
> Subject: [TowerTalk] How much do trees really affect verticals
>
> I have been clearing some land to plant more maple trees for my sugar bush
> to make maple syrup in the spring. While I resting I thought of all the
> room I am clearing for a 4 square for 75/80. There are 40 some deciduous
> trees on the land which is about 150 feet by 350 feet. Prime farmland,
> stream bottom with about 4-5 feet of topsoil. Its about 200 feet from my
> house/shack.
> How much are those trees really going to affect the antennas?
>
> Gregg K9KL
>
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