# Problem about characteristic impedance

Discussion in 'Electronic Basics' started by Archer, Sep 26, 2004.

1. ### ArcherGuest

how to measure the characteristic impedance of a coax?
I'm starting to study the rf circuit design.

2. ### Rich GriseGuest

I've always found a time domain reflectometer gets me close enough.

Good Luck!
Rich

3. ### Roy McCammonGuest

you the impedence (complex) with the far end
shorted and with it open and the characteristic
impedence is the (complex) geometric mean of those
two measurements.

4. ### ArcherGuest

may i measure the impedence using meter?
and how would it be done that measure the open far end coax?

5. ### Roy McCammonGuest

I suppose you might do with a vector volt meter. Not sure.
Been too long since I used one. I'd use a scope.
you don't measure at the far end. you just short the far end
or open the far end.

6. ### Alexei ZyuzinGuest

Or you also could measure the inductance of the inner conductor and
capacitance between the inner conductor and the shield. Z0=sqrt(L/C)

Regards