[TowerTalk] Change in Frequency As Antenna Height Rises

[Ed Sawyer]

I have the Force 12 EF240X.  This is the wire loaded elements that are about
45 ft long and a 24ft boom.  I have tuned this antenna and have found the
resonance (not the 1:1 SWR) changes pretty significantly from 15 ft to 35 ft
to 80 ft.  I don't have my original notes, but I recall seeing at least
100khz total shift.  However, the 35 to 80 ft shift was maybe 20 - 25khz vs
the 15 to 35 ft shift being the rest.  I always attributed it to the
additional ground coupling changing the net "loading" on the shortened
elements that got less impactful as it got higher.

 

I have not used the antenna in a couple of years.  It was potent but the
construction weaknesses were an issue.  Its on the "refurb" list but not a
priority.

 

Ed  N1UR