Ohm rating on coax cables.

Thread Starter

Nathan Hale

Joined Oct 28, 2011
146
Hi Everyone! Hope all is well with u folks. I have a question about coax cables/ wires . I notice a lot of times that a coax cable of lets say 75 feet has a resistance rating of 50 ohms. What does the ohm rating mean? After all a wire is a wire and not a resistor. What is this resistance rating indicating?

Thank you for all you replies.
 

Brownout

Joined Jan 10, 2012
2,364
That's 50ohm impeadance, it's not the resistance of the wire. This is determined by the inductance and capatcitance of the coax. Typically, the electronics' impeadance are matched at each end of the coax (aka transmission line)
 

bertus

Joined Apr 5, 2008
20,053
Hello,

The resistance given is not the real resistance, but the impedance of the cable.
This impedance depends on the diameter of the inner wire, the diameter of the shielding and the dielectricum in between them.
More info can be found on this page of the EDUCYPEDIA:
http://educypedia.karadimov.info/electronics/cablingrf.htm

On the bottom of the page is the formula to calculate the impedance.

Bertus
 

Papabravo

Joined Feb 24, 2006
12,405
Impedance is a characteristic of AC circuits, and it has absoutely nothing to do with DC resistance. In addition DC resistance is a real number measured in Ohms. Impedance is a complex number whose MAGNITUDE is also measured in Ohms. It also has a phase angle measured in radians or degrees.
 
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