On Sat, 11 Nov 2006 18:04:47 -0800, Roy Lewallen
wrote:


Trap loss when used in an antenna is a function of many factors, and
there's really no practical way to determine what it'll be except for
modeling. Of course you have to know the equivalent L, C, and R or Q.

Roy,

Sure. I should have mentioned that after trying NEC models to get a
low VSWR solution for just two bands (one twice the frequency of the
other) I gave up figuring that it was likely that an ATU would be
needed in any case, and the traps were just an unnecessary
complication.

As you know, trapped antennas are sometimes explained by considering
the traps to be equivalent to frequency selective switches that are
o/c or s/c at certain frequencies of operation, and conveniently
disregarding the conductors on the outboard side of the o/c switches.
It is a simplistic view, it does not lead to a design that works, nor
does it explain designs that do work, but it remains the most popular
explanation to be heard on air in my experience.

Owen
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