RCDD · Question #182
What is the appropriate impedance of coaxial cable for use with broadband distribution?
The correct answer is B. 75. Coaxial cable used for broadband CATV distribution has a standardized impedance of 75 ohms. This impedance is distinct from the 50-ohm coax used in RF and data networking applications.
Question
What is the appropriate impedance of coaxial cable for use with broadband distribution?
Options
- A50
- B75
- C100
- D150
How the community answered
(27 responses)- A7% (2)
- B74% (20)
- C4% (1)
- D15% (4)
Why each option
Coaxial cable used for broadband CATV distribution has a standardized impedance of 75 ohms. This impedance is distinct from the 50-ohm coax used in RF and data networking applications.
50-ohm coaxial cable is used in RF transmission, wireless antenna systems, and baseband data networking - not broadband CATV distribution.
75-ohm coaxial cable is the industry standard for broadband video and CATV distribution systems, as defined by SCTE and TIA standards. This impedance is optimized for video signal transmission and matches the input impedance of CATV equipment such as amplifiers, splitters, and set-top boxes. Using mismatched impedance causes signal reflections and degraded performance.
100-ohm is the impedance of balanced twisted-pair cabling such as Category cables used for Ethernet, not coaxial cable.
150-ohm is not a standard impedance value for any common coaxial cable type used in commercial distribution systems.
Concept tested: Coaxial cable impedance for broadband CATV
Source: https://www.scte.org/standards/library/catalog/scte-2-2020-environmental-qualification-testing-for-broadband-cable-telecommunications-equipment/
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