Electronic – Why did CATV standarize in 75 ohms and everyone else in 50


All of the CATV industry runs on 75 ohm systems, while most of the rest of the radio world uses 50 ohms.

Why was this standard chosen?

I was wondering this because good quality RG6 cable can be obtained everywhere for very little, compared to decent quality 50 ohm cabling.

Best Answer

How is transmission line impedance selected? explains why transmission line impedance matters.

The CATV industry deals with low-level signals, so it cares ONLY about loss and not at all about power-handling. That's why they chose 75Ω transmission lines.