At least, it seems my concerns about the relative youg age of the F12
company (compared to the others), were unfounded, as I have not seen any
negative comment about robustness.
I bought the beam report from N0AX and K7LXC, and the Force 12 antennas
certainly blow the competition away. The only measureable advantage of my
24' boom TH7DX on the shorter F12 antenna (C3, 18' boom) is the front to
back ratio. Most everything else is a wash. They have the same number of
elements. The TH7DX has more active elements on each band, so the front to
back is more typical of a 4 elements beam, but it has traps, so the less
lossy C3, with its 2 active elements on 20 and 15, makes up for the lower
theoretical gain with better efficiency.
Before putting my used TH7DX up, based on suggestion from N1MM and others, I
carefully took apart all the traps, cleaned them thoroughly with a soft wire
brush, put no-ox under all the metal-to-metal interfaces and protected the
coils with clear varnish spray before putting the tubes back over.
Considering that the antenna was about 15 years old (it had been thoroughly
cleaned 7 or 8 years before I bought it), it was in great shape. The
previous owner had put no-ox on all the mating surfaces of the various
tubes, which made disassembly a snap, but not under the screws holding the
coils, and that interface had some corrosion on about half the traps.
73,
Didier KO4BB
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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