Not sure there is a "rule of thumb". If I had to
guess, I would say it depends on the antenna design
and the frequency...
One datapoint: just this weekend my Cushcraft 15-4CD
dipped low in frequency (long) when near the ground -
as I hoisted it up to 20 feet, the frequency moved up
to design spec - graphic Antenna/SWR analyzers are
great! The bottom of the VSWR curve also dipped lower
in magnitude as I raised the antenna (this was expected
and desired of course).
Until I had (or someone presented) the measurements to
prove it, I wouldn't necessarily count on the
direction or magnitude of that freq shift for an
antenna of a different design (say a dipole or maybe
even a Hygain 105BA).
Mike N2MG
K4OJ wrote:
> Been building up some yagis... what is the rule
> of thumb for how much the frequency will change
> from where it "dips" on the ground versus up
> in the air?
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