Hi Jim,
I am moving my station to Maine -- and asked the "QST Doctor" about trees
and antennas back in January 2007. There is a response in the July 2007 QST
"The Doctor Is In" column. I also received this correspondence from W3ZZ,
Gene:
------------
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].
...snip...
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.
...snip...
Good luck.
73 Gene W3ZZ
------------------------
73 -- Larry -- W1DYJ
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <towertalk@contesting.com>
Sent: Sunday, April 05, 2009 8:09 PM
Subject: Re: [TowerTalk] EZNEC- needs improvement
> On Sun, 5 Apr 2009 16:00:50 EDT, RLVZ@aol.com wrote:
>
>>Yes- do have poor performance with verticals, but you mentioned that you
>>live in a heavily wooded area. Verticals work poorly in heavily wooded
>>areas so I don't believe that's a fair environment to compare verticals
>>to horizontals.
>
> I've looked for published scientific work on this and all I've found
> addresses VHF/UHF (either military, 2-way, or cellular applications). What
> I've seen generally agrees that absorption that increases with frequency,
> and that correlates with my experience. Can you point me to anything that
> addresses MF or HF in forests and heavy vegetation?
>
> 73,
>
> Jim K9YC
>
>
> _______________________________________________
>
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>
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