Bob,
Might I add to to LB's suggestion that if youconstruct a trap dipole, use a
high quality plenum coax to construct your traps. The silver-braided,
teflon-insulated stuff may cost a few bucks a foot, but it will provide
superior performance. The large braid will perform extremely well as a low
resistance inductor, while the dielectric properties will provide excellent
capacitive properties. This is a good place to spend money on expensive
coax!
To keep from cutting the expensive stuff too short and having to start over,
recommend finding some cheaper coax with similar capacitance value per foot
and use that to determine your length requirements. Always start a little
long with the expensive stuff. Some use PVC as a coil form, but it has known
dielectric problems. You may find something better. If all else fails, you
can wrap several turns together with cable ties, and attach to a long
porcelin insulator which is also used for strain relief.
Coaxial traps also offer superior weather-proofing over discreet components,
and are comparable in cost. Short of nuclear war, they'll probably last
forever!
73, Paul
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