Jim Lux wrote in news:j846r5$7h3$1
@news.jpl.nasa.gov:

There's a goodly bit of empiricism in trap design.

And a goodly bit of misinformation in some of the traditional ham sources.

I have had an interest in the so called coax traps, and just in the last
week or so, make some headway with some good measurments of the underlying
inductor formed by the coil of coax shield. There were some surprises. For
those interested, see http://www.vk1od.net/antenna/coaxtrap/index.htm .

Short of performing Medhurst style measurements on a range of inductors,
there is no way to be sure that the effects observe apply generally, or
what a more general model might be.

Owen