This is an excellent thread.
dick.green@valley.net writes on 31/08/99:
>(snip)K4SQR did tell me that the elements themselves should be at
least 1/2 wavelength from any metal structure, especially a tower.<
However, where it is a tower (as opposed, say, to a metal building)
K4SQR reminded me of the coverage in the ON4UN book (I need to get
the 3rd edition--this was in the 2nd at least) on detuning towers.
One of the routes was using an MFJ artificial ground at the base of
the tower, connected to a wire that runs up the tower and connects to
the tower there. You tune it for MINIMUM flow at the band of concern.
My 160 4sq still hasn't gone up, partly because I wanted to get the
tower sited. When it goes up I will see what the meter on the MFJ
reports, if anything, on coupling when the 4sq is transmitting, and
no doubt use it even if the coupling is fairly small.
>Although 4-square owners tend to be very exacting on the feedline length and
element spacing (I know I was), I really don't think that they have as much
impact on the frequency at which dumped power is minimized as element tuning
does.<
My experiences bear this out. As a CW enthusiast, I spaced my 80M 4sq and
its phasing lines for low-end, not the usual compromise of 3650. My F12
verticals (which seem to perform very well) are shortened and require
retuning. I have had NO difficulty getting dumped power down to very
miniscule levels by retuning the verticals only.
73,
Jim, VE1JF/XJ1JF
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