----------
From: John Langdon[SMTP:jlangdon@outer.net]
Sent: Monday, August 10, 1998 12:05 PM
To: towertalk@contesting.com
Subject: RE: [TowerTalk] Towers & Trees
John and others:
Just another fly in the ointment. Don't forget the attenuation that a forest
of trees brings, especially on VHF and UHF! I remember driving along a high
mountain road in Sequoia (sp?) National Park while talking through a two meter
repeater that was about 100 miles away in the direction that I could see almost
that far. Every time a grove of Redwood trees came between me and the horizon,
the signal would go from full quieting to nil.
A few years later I put up a moonbounce array for two and six meters with 4
yagis each on an H frame. I had a 90 foot self-supporting crank up tower and
lived next door to a forest of Alder trees (and K7LXC on the other border
line). Time and time again I tried to work EME through the trees (even in
winter when the leaves were gone) at moonrise only to be disappointed. Most
every time I raised the tower up to the point the array was looking out over
the canopy of trees, the EME signals just popped right out of the noise.
Unfortunately, I never had an HF antenna on that tower to see what the effects
were for HF and besides, it would be hard to separate the ground enhanced gain
from the tree attenuation. If anyone has any hard information on attenuation
of forests on HF signals, I for one would like to hear about it.
I have never forgotten those earlier experiences and when I moved to Montana I
looked for property with no natural trees and now I sleep easy every night when
the winds are blowing about 80 mph or so, knowing that no trees will fall
across the guy wires. With no trees on my property, I am also able to better
enjoy looking out at the forests on the mountains at a distance. Now if I
could just convince my wife how great it is!
73/Mike, N7ML
You should consider the trees to have a 100% set back requirement ala some
municipalities: if the tree would fall across a guy or anchor during a full
length fall in any direction, it should be gone. Then visualize the trees
10 years from now and apply the same standards to them now. Be mindful of
limber limbs that during high winds could rub against guys (especially
Phillystran). Watch the trees during a thunderstorm with 50+ mph winds and
you will be amazed at the excursions some of those limbs can make.
I cleared 100's of junipers out of the way, and about a dozen oaks that did
not meet the above requirement (but I'm set for firewood for a while!).
Even if you have an ordinance that requires replacing any tree you remove,
it is still cheaper than replacing the tower and guys, or disputing an
insurance claim denial as to whether or not your failure to remove the
trees was not good installation practice. We would have never been able
to run the tram line (much less the back guys) or get the antennas up on to
the tower if we hadn't removed some of the tree cover. I still don't have
all my slopers up because of the hassle of getting a line up and over the
all the trees and through the antennas mounted on the tower, but I draw the
line at removing trees for that, at least at this point. I am planting
more trees than I removed (voluntarily) to shade the shack and reduce
visibility of the antennas from the road.
BTW, sometimes the tree huggers are good for DX. The city is buying
multiple 1000's of acres near my remote QTH to make sure they never get
developed, which for me means less QRN and fewer potential TVI target
devices.
73 John N5CQ
-----Original Message-----
From: Bill Fisher - W4AN [SMTP:w4an@contesting.com]
Sent: Monday, August 10, 1998 11:01 AM
To: LYN
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Towers & Trees
When it comes to trees, my advice is to figure out what trees you need to
take down. Then take 50% more. This advice was given to me by K5ZD and
I chose to ignore it. The tree-man was happy I did.
73
W4AN
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|