"Roy Lewallen" wrote in message
...
Cecil Moore wrote:

Can a doorknob cap rated at 20 KVDC be used to
resonate a small loop?

Sure, but I think you'd end up with a pretty poor antenna.

I don't know for sure, but guess that doorknobs are typically made from
Z5U or similar ceramic. If so, the capacitance is a strong function of
both temperature and voltage. Therefore, the loop tuning will change with
both those factors. I'd also guess that the Q wouldn't be too hot, so
you'd also incur a lot more loss than you would if you used an air
dielectric part.

Roy Lewallen, W7EL

It's not just the voltage but the RF current too. If this is a compact loop,
the RF current can be high and just because a capacitor can withstand a high
voltage doesn't mean it an also pass a high RF current. The spec's I've seen
call out the max voltage and a max RF current for transmitting capacitors.


--
John Passaneau W3JXP
State College Pa.