What is RG?
Stands for Radio Guide, a U.S. Army specification for grades of transmission lines.
RG specifications refer to forms of coaxial cable used in networking, as in the following examples:
RG-8: Also known as N series cable, which is a coaxial cable with an impedance of 52 ohms. RG-8 looks like thicknet Ethernet cabling but is actually a lower grade and does not perform as well. True thicknet cabling is labeled as IEEE 802.3 cabling, has a diameter of 3/8 inches, and is yellow or orange.
RG-58: Often called thinnet, which is a form of coaxial cabling with an impedance of 50 ohms and a diameter of 3/16 inches used in 10Base2 Ethernet networking. Subdesignations of this standard include RG-58 /U, which has a solid copper core, and RG-58 A/U, which has a stranded copper core.
RG-59: Another name for CATV or cable television cabling, which is a form of coaxial cabling with an impedance of 75 ohms.
RG-62: A form of coaxial cabling with an impedance of 93 ohms that is used in ARCNET networks.