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 bulkradio frequency 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 and cable sold today under the RG-6 label is unlikely to meetmilitary specifications. In practice, the term RG-6 is generally used to refer tocoaxial cables with an 18AWG center conductor and 75ohm characteristic impedance.
Applications
A common type of 75 ohm coaxial cable is cable television distribution coax, used to route cable television signals to and within homes. CATV distribution coax typically has a copper-clad steel center conductor and a combination aluminum foil/aluminum braid shield, typically with low coverage. 75 ohm cables are also used in professional video applications, carrying either base bandanalog video signals or serial digital interface signals; in these applications, the center conductor is ordinarily solid copper, the shielding is much heavier, and tolerances are more tightly controlled, to improve impedance stability. Cables typically have connectors at each end.
Types
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. Messenger or aerial may contain some waterproofing but is distinguished by the addition of a steel messenger wire along its length to carry the tension involved in an aerial drop from a utility pole. Plenum wire comes with a PTFE outer jacket designed for use in ventilation ducts to meet fire codes.
Attenuation/signal loss
Cables attenuate a signal in direct proportion to length. Attenuation increases with frequency due to skin effect.
