>Considering that any 160M aerial located temporarily in a forest is likely
to be
>short and tuned and very narrow in bandwidth and you have the most likely
>solution - the aerial goes off resonance compared to what it does in the
open.
>This might apply particulalry to a mobile which does not have interactive
VSWR
>tuning
Here's my empirical experience with a base loaded 160M groundplane
w/elevated radials. It consists of 66ft of copper pipe sections up through
the interlocking branches of a double trunked 90 foot pine tree. When the
environment is moist, e.g. above 20 deg F, the
antenna system shows a 2:1 SWR over about 70KHz. When the temperature drops
below 20 and stays there for a few days, the SWR at resonance rises to 1.8:1
and the bandwidth does get noticeably narrower. The tree
probably does cause some losses, but I have not seen any significant shift
in
resonant frequency. On air performance compared to a reference
dipole didn't change as moisture/temperature varied. The main "problems" are
falling limbs slicing off one or more radials depending on how close they
fall to the base, and wondering what broke when I don't remember that it's
been cold outside for a while.
Bruce W1CSM
w1csm@arrl.net
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