Hi Dave,
> I have received several emails today warning of problems with W2AU
> (Unadilla) traps.
> Power handling and reliability seem to be the major complaint.
> I only have experience using them in elevated radials I built for Bob W6RJ
> to use with his Titanex 160/80/40m vertical. He used them on his
> DXpedition to FO0 without any problems, however one was physically
> damaged.
Apples and Oranges.
Stress in the trap is inversely proportionial to the surge impedance
of the conductor containing the trap and the power applied to that
conductor. The lower the impedance at the current loop, and higher
the power applied to each conductor, the more stress in the trap.
Low elevated radials have higher surge impedance than a high
dipole (because of earth induced power losses) and also divide
feedpoint power into multiple radials.
Worse case stress is in an antenna with low impedance at the
current maxima and only one conductor carrying all the power. An
example would be a vertical with a good ground system. The trap in
it has to be twice as "good" as a trap in a dipole to handle the
same power. The saving grace in the setup you describe was earth
loss and multiple wires (radials) that "shared" the power.
73, Tom W8JI
w8ji@contesting.com
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