[TowerTalk] Rule of thumb?

[Mike Gilmer - N2MG]

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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