At NR4M we haven't gotten around to getting a more permanent 160M antenna in
place, so we've been using a sloping wire vertical or most recently a TEE.
There is a catenary between the 120 foot 15M tower with a stack of three 5
el yagis on it, and the 20M tower. There's probably 150 feet between the two
towers and the vertical portion of the TEE is about twenty five feet from
the 15M tower.
During the CQWWSSB contest we had about five radials connected to the
antenna. Ken K4ZW who operated that contest from NR4M said SWR was good
around 1850 and the 2:1 points were 1800-1900.
We layed 45 "insulated" radials on the ground under the vertical section of
the TEE. SWR at 1850 is now about 2.5:1 and using an AEA analyzer, appears
to be resonant at 3100 with an swr of 1.2:1.
We need to look at this some more, but first conjecture is that for some
reason we're seeing more interaction between the 15M tower and the TEE now
that there's a better RF ground beneath them.
Does it make sense that the addition of 40 radials would make the reasonant
frequency appear to drop from 1850 to 3100?
73 de Larry K7SV
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