On Tue, 24 Oct 2006 14:01:03 -0400, Pat Chiles wrote:
>Has anyone done this before, without insulators, and did the
>antenna give expected results?
Since my new QTH is in a redwood forest, I've been studying this
out of necessity. :)
>From my experience, both here and at other QTH's, and from what
I've seen "in the literature," HF antennas still work in the
presence of foliage, although they might be pulled down a bit in
frequency (a few percent), so might need to be cut slightly
shorter. I also saw a piece in one of ARRL's antenna compendiums
noting that a dipole that ended quite close to the trunk of a tree
that supported it was detuned in this manner. In general, wires
that run close to, and in parallel with, the trunk of a tree, or
to big branches, are more likely to have their performance
degraded.
Also, degradation/interference increases with frequency, so lower
band antennas will be affected far less than higher bands. For
example, I see no issues on the HF bands, 6 meters works for me, 2
meters is starting to see attenuation, 440 is stinko, and no one's
cell phones work up here. My friend, WA6NMF says, "think -3
dB/tree at 900 MHz."
On 160 and 80, my best performing antenna is a 70 ft vertical.
It's in the middle of a clearing of roughly 100 ft radius, but
surrounded by 100-125 ft redwoods, oak, fir, and madrone.
73,
Jim Brown K9YC
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