characteristics impedence

hi all,

can anybody plz tell how do we measure cahracteristic impedence of a cable, may it be coaxial, stp, utp or power looks impedence matching and trying to get the maximum power. i s there any other way?

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If you really want to do this look here:


Reply to
Tom Biasi

Well, you can safely forget about the concept for an equipment power cable.


Reply to

Just measure it.

1] Measure the "L" with the lead ends short circuited. 2] Measure the open circuit "C" 3] Then Zo= square root of L/C

Some I did last year ...

2mtr of "75ohm" coax L=1.48uH C=146pF ... Zo=100ohm* 2mtr of 50ohm coax L=0.83uH C=168pF ... Zo=70ohm 2mtr of 'twin flex' L=1.23uH C=70pF ... Zo=132ohm 2mtr of 'mains cable' L=2.84uH C=281pF ... Zo=100ohm 3mtr CAT5 patch cable L=2.51uH C=157pF ... Zo=126ohm

(measured twice, still same result!)

Reply to
john jardine

"john jardine"

** Likely the frequency you used for the L and C measurement was not in the normal RF range.

Zo for co-ax tends to rise at low RF and audio frequencies.

....... Phil

Reply to
Phil Allison

I would either look it up in the cable spec, calculate it, or measure it with a TDR.

Good Luck! Rich

Reply to
Rich Grise

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