On Wed, 04 Apr 2007 21:48:08 -0700, Bryan wrote:

A stub of coaxial cable will work... approximately 30pF/foot for 50 ohm
types... approximately 20pF/foot for 75 ohm types.

Good evening, Bryan.

Thanks, but there are a couple of problems... the antenna will be for 160
through 40 and so two of the traps will be for 80 meters... I forget what
the capacitance will be but I think it was somewhere in the 200 pf range.
Also, the antenna is meant to be portable, and so the traps need to be as
physically small as practical. Also the power will usually be low... as
low as 5 watts, usually no more than 50 and never more than 100 watts...
so I guess I need to make the antenna as efficient as I can... kind of a
contradiction in terms for trapped antennas especially where the traps
need to be physically small.

If I could find the doorknob capacitors for a reasonable price that would
be ideal, but $15 each is way too much.

On the other hand, the ones from RF Parts are all at least 4 KV, and up
from there (40-50 KV). I don't know how to accurately calculate the
voltage rating I'll need (I'll post that as another question under another
topic), but my guess is that for 100 watts max, I don't need 5 KV, and may
not need 1 KV.

Who else besides RF Parts has these things and has a decent website?