[time-nuts] 50 Ohm vs. 75 Ohm RF cable

Tom Miller tmiller at skylinenet.net
Tue Feb 7 23:00:00 UTC 2012

> There is no particular advantage in one or the other, at least not
> for most applications. It's tradition that measurement and (most) RF
> gear uses 50R, while TV and radio uses 75R. (there was once a reason
> for this, but i don't know it).


The reason there are two primary impedance's in use comes from the fact that 
75 ohm cable has the lowest loss characteristics and 38 ohms can carry the 
highest power. For cable systems, they desire the lowest loss for obvious 
reasons. The 50 ohm was chosen as a compromise between low loss and power.

I say this from memory so the exact values may vary a few ohms. The 
information can be found on the net.


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