RG-6/U is a common type of coaxial cable used in a wide variety of residential and commercial applications. An RG-6/U coaxial cable has a characteristic impedance of 75 ohms. The term, RG-6, is generic and is applied to a wide variety of cable designs, which differ from one another in shielding characteristics, center conductor composition, dielectric type and jacket type. RG was originally a unit indicator  for bulk radio frequency (RF) cable in the U.S. military's Joint Electronics Type Designation System. The suffix /U means for general utility use. The number was assigned sequentially. The RG unit indicator is no longer part of the JETDS system (MIL-STD-196E) and cable sold today under the RG-6 label is unlikely to meet military specifications. In practice, the term RG-6 is generally used to refer to coaxial cables with an 18 AWG (1.024 mm) center conductor and 75 ohm characteristic impedance.
A common type of 75 ohm coaxial cable is cable television (CATV) distribution coax, used to route cable television signals to and within homes. CATV distribution coax typically has a copper-clad steel (CCS) center conductor and a combination aluminum foil/aluminum braid shield, typically with low coverage (about 60%). 75 ohm cables are also used in professional video applications, carrying either base band analog video signals or serial digital interface (SDI) signals; in these applications, the center conductor is ordinarily solid copper, the shielding is much heavier (typically aluminum foil, and 95% copper braid), and tolerances are more tightly controlled, to improve impedance stability.
Cables typically have connectors at each end.
Like most cables, RG-6-style cables are available in several different types designed for various applications, including:
Plain or house wire is designed for indoor or external house wiring.
"Flooded" cable is infused with water blocking gel for use in underground conduit or direct burial.
Cables attenuate a signal in direct proportion to length. Attenuation increases with frequency due to skin effect.
|Frequency (MHz)||Attenuation (dB/100 ft)|
|1||0.2; 0.4 for CCS|
- 'Mike Meyers' CompTIA Network+ Certification Passport', by Glen E. Clark, edited by Christopher A. Crayton, McGraw-Hill, 3rd Edition, 2009, page 32. "Specific coax types were developed for the Ethernet standard, but a number of radio cables have very similar characteristics, and these so-called radio-grade (RG) cables also became associated with Ethernet."