there's no "probably" to it! It is lowest (in frequency) closet to the
ground.
I have now range tested 2 15 meter 6 elements and 2 20 meter 5 elements as
well as tested a 40 meter dipole and 4 element by raising them from 32" (on
saw horses) to just mounted at the low point on the Razor mast on the side
of the test tower at ~8' and then up to 37' at its max height.
I've seen changes of 100Khz on 15 meters going from 8' to 37'. I'm sure it
is where it will be from there on up. The SWR might change due to the
changes in R/X but the frequency be about the same there and up.
On 20 meters a change of 115 Khz from 8' to 37'. I would suspect it is where
it will be as well (when at 37') - no additional shift from there on up.
Finally on 40 meters I saw as much as a 300Khz change from 32" (on saw
horses) to 37' on just one element of the yagi... I believe it was about 150
Khz from 8' to 37'. And think there might be an additional 20 Khz or so
shift from here on up to probably 50' or so.
On the 40M4LLDD I have an SWR of 1.15:1 at 7.0 - pretty flat from there to
7250 where it is still 1.3:1 and at 7300 its 1.9:1. (CW-LoPhone tuning
chosen for better FB at DX end 7.000 - 7.170 - although still pretty darn
good up to 7.3!)
Gary
K9RX
-----Original Message-----
From: Don W7WLL
Sent: Saturday, May 28, 2016 5:29 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Change in Frequency As Antenna Height Rises Above
Ground
Well, as usual, a number of opinions are offered/stated/given as
fact/experienced in TT and direct email messages I've read so far. Most
agree that, at least for wavelengths below at least 1/2, the effect will
probably be a decrease.
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