This subject has been discussed here plenty of times in the past, and the
consensus has always been that trees and other foliage near a 160m antenna
has a negligible effect on the transmitted signal. That's what I have
believed for some time.
This was discussed last month at
http://www.eham.net/ehamforum/smf/index.php?topic=90638.0 . This article
by
Carl Luetzelschwab K9LA appeared in the March/April 2006 NCJ titled "Low
Band Antennas and Trees". LINK:
http://k9la.us/Low_Band_Antennas_and_Trees.pdf .
Look at the chart and discussion there. It flies in the face of previous
observations by a lot of intelligent Topbanders.
I'm not at all saying that I agree with this. But it certainly does seem
that after the leaves came out and the weeds grew around my 160m
inverted-L, my signal on the Reverse Beacon Network is nowhere near what
is
was in the early spring. I doubt that it has anything to do with the tall
weeds under my elevated radials or the oak leaves near the inverted-L.
But never mind all that; what do you gentlemen think about this article? I
don't know what to think.
73, Mike
Mike, from what Ive read on here from many intelligent topbanders, and also
commented on in the past, is that trees definitely have an effect on
vertical antennas. I'll certainly have to agree with the "other" Carl.
Other forums have had similar agreement.
Ive no 160M experience with them.
Someone with the time can research the US Army experiments in the 50's that
was published in either CQ or QST, I forget which and dont have the time
today to search. It was done at Ft Monmouth in NJ and also in the Canal
Zone.
To repeat my own experience it was in the early 80's. I started out with a 6
wire 12" diameter cage vertical for 80 hung from a branch of a pine tree
about 1-2' away from the trunk. Even with 64 on ground radials performance
was dismal. Moving it out to about 8' and I could work DX without having to
wait until I was the only one calling. The resonance point also changed.
There were only 2 trees in the back yard, both pines, and the other was very
cooperative with a branch a quarter wave away so another cage was hung at
the same distance. This was phased with the other using coax and relays for
2 cardiod and a broadside figure 8 pattern and was competitive in pileups.
I then used the array as half waves on 40 in a pair of figure 8's but was
never satisfied and felt the trees were absorbing considerable RF. A 4el 40M
KLM at 120' soon took care of that problem.
In retrospect I have to believe the trees were still affecting 80 to some
degree.
The only test equipment I had at the time was a Bird 43, a noise bridge, and
a borrowed Knight T-150 as I was not about to haul a 100+ lb CE-100V back
and forth from the basement.
Carl
KM1H
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Topband Reflector
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