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Original Message
RE: what make coaxial cable impedances of 50 ohms and 75 ohms ?
Posted by Duster on January 16, 2017 at 20:01:35:
It's the relationship of the center conductor with the braided shield, meaning the plastic dielectric that separates the two, and how well a perfectly round shape is kept along the entire length of the 75 ohm cable. It can be a bit confusing, since there does not seem to be a clearly identifiable relationship that meets the eye. There are 75 ohm mini-coax cables that look very compact vs. an RG-59 or RG-6 for that matter that can also seem to look a bit arbitrary in nature. However, if proper measurements are followed during the design and manufacturing process, a proper 75 ohm characteristic impedance can be determined and achieved.