Not much more info. These are definetly feedthru caps and they want
them verified to be Zo of 50 +/- 10. ( We're a small parts testing
house) Maybe they're meant to be signal feedthrus? I assumed they were
for power lines ,but you're right; being Zo = 50 they must be for
signals?
On Tue, 06 Jul 2004 16:46:25 -0500, Bob Liesenfeld
wrote:



wrote:

I have a bunch of small feedthru caps that I need to measure their Zo
to assure it's 50 +/-10 ohms. Any thoughts on how to do it? I'm going
to try to put a 50 ohm load on them and look at them with a network
analyzer. I should be able to get it's Zo from the VSWR, no? Any other
ways?

Hmmmmm....Are you sure you mean feedthrough capacitors? My
understanding of FT caps is that they are a very low Z from the
terminal(s) to ground while allowing a DC voltage to pass through. I
don't see where you are getting the 50 Ohm Z value. But, perhaps I have
missed something. More info?

Bob WB0POQ

We're a small parts testing
house)
I assume you do testing for profit, this is an Amateur Radio newsgroup. But,
since you asked :-).

These are definetly feedthru caps and they want
them verified to be Zo of 50 +/- 10.

The Zc of a capacitor (capacitive reactance) is frequency dependent. Not sure
what Zo of a cap. refers to. At some frequency the capacitor will have a
Zc=1/2*pi *f*c. I am sure you know that. An ideal capacitor will have a
Zc=0-jZc. A real world capacitor will have a non-zero real part of R+-jX. To
have the real part 50 ohms( Zo), must mean the frequency is in the VHF region
or higher. To measure what you want, you need a Z meter with the capability of
measuring the complex impedance of the feed-thru capacitors at the frequency of
interest. I have an antenna analyzer that I use for that sort of thing, but it
only reads capacitive reactance at the frequency of interest.
Not sure if this helps?
73 Gary N4AST