At 04:53 PM 12/12/96 -1000, you wrote:
>The military has done extensive studies regarding RF absorption
>by foliage. 20 years ago while in Coast Guard Radioman school
>I recall some instruction regarding this; my memory is a bit
>dim but what stands out is that all antennas should be kept
>clear of all growth, and don't depend heavily upon ground
>wave propagation over forested areas.
"Don't sweat the small stuff"
I remember this too from US Army Signal School, fall 1974. However, the key
factor was frequency. Since most platoon and company communications is VHF,
this was the frequency range of greatest concern. PRC 25/77 series radios
use either a long rigid whip or a flexible steel antenna (the one you often
see bent over the RTO's shoulder.) The long whip was better for covering
greater distances. The steel whip is, at best, like a rubber duck,
convenient but not the best DX antenna.
I have somewhere a "Green-Beenie" (best bunch of guys to ever train me) FM
that shows how to make field expedient antennas using telephone wire and
other electrical conductors. The book makes extensive use of trees as
support structures. It also shows directive arrays as well as a number of
other interesting antennas. My guess is that this book was written from the
ARRL Antenna Handbook. I don't remember it saying much about foliage or trees.
Most HF communication in the Army is Battalion to higher commo on secure
RTTY. These rigs are located usually in 5/4 ton trucks in a shelter. I have
seen them in jeeps too but for voice communications. These vehicles use a
8-10' whip that is matched with a tuner. There is also a steel tape dipole
but usually you don't have time to install it as you are constantly on the
move. In today's world, you can bring fire on a stationary radio target
within several minutes. There is simply no time to erect antennas or find
clear open spots for establishing communications. You locate your
transmitter in the woods (for self preservation) and try to establish your
commo link.
I also remember, from the dark recesses of my mind, an article in QST that
addressed using a tree as an antenna. McCoy and DeMaw were involved and the
picture showed a tree with a coil type matching device attached. I can't a
better give a citation; however it was from either early 60's late 50's.
Finally, I wouldn't sweat running my Beverages in the woods and thru the
trees. A UHF site yes, Beverages for 160, no.
My Beverages are supported on, thru, around and by trees. They work and work
well. Sure I could spend hours optimizing them. What good would it be? First
wind or ice storm, branches will fall and back to work I go making repairs.
Keeping it simple but maximizing performance should help guide you. Make
sure your ground is good. Make sure you match the feedline to the antenna
properly. I have seen far too much about tweaking, twisting, optimizing
that ends up wasting time and money.
Yesterday on the Tower reflector a fellow suggesting adding additional guys
to his 100' tower, now guyed at 33, 66 and 100'. His question was would it
be stronger? Of course, but from what and for what? Would it be worth the
time and expense, I doubt it.
The book "Zen and the Art of Motorcycle Mechanics" suggests that if "it aint
broke, don't fix it." My suggestion is don't sweat the small stuff. Trees
should be enjoyed, not cleared. Run your antennas thru the woods. Do the
best you can and ad Bob Kile and others have said here, enjoy yourself, keep
it all in perspective.
Craig
Cpt USAR
Signal Corps
1974-1987
Craig Clark
Hu-rah! now W1JCC
ex NX1G, N1ACH, WA1QWW, WN1IGG
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