The F connector (also F-type connector) is a coaxial RF connector commonly used for “over the air” terrestrial television, cable television and universally for satellite television and cable modems, usually with RG-6/U cable or, in older installations, with RG-59/U cable.
The F connector is an inexpensive, gendered, threaded, compression connector for radio frequency signals. It has good 75 Ω impedance match for frequencies well over 1 GHz and has usable bandwidth up to several GHz.
Connectors mate using a 3⁄8 in-32 unified extra fine (UNEF) thread. The female connector has a socket for the center conductor and external threads. The male connector has a center pin, and a captive nut with internal threads.
The design allows for low-cost construction, where cables are terminated almost exclusively with male connectors. The coaxial cable center conductor forms the pin, and cable dielectric extends up to the mating face of the connector. Thus, the male connector consists of only a body, which is generally crimped onto or screwed over the cable shielding braid, and a captive nut, neither of which require tight tolerances. Push-on versions are also available.
Female connectors are typically used on bulkheads or as couplers, often being secured with the same threads as for the connectors. Thus can be manufactured as a single piece, with center sockets and dielectric, entirely at the factory where tolerances can easily be controlled.
This design is subject to the surface properties of the inner conductor (which must be solid wire, not stranded) and is not corrosion resistant. Hence waterproof versions are needed for outside use (for example, on antennas). Corrosion resistance, reliability of connector electrical conduction and water resistance can be improved by coating all bare copper wires and the connectors themselves with silicone grease.
The cable and satellite television entities (as a near standard practice) use compression fittings with F connectors on customer premises. In Europe, block down-converted satellite signals (950–2150 MHz) from LNBs and DC power and block signalling from satellite receivers are near exclusively passed through F connectors.
F connectors are probably the most suitable for domestic terrestrial, cable, and satellite TV installations where the delivery of very high frequency information is required. Belling-Lee connectors (IEC 169-2; used on European terrestrial receivers) are not well suited for long-haul building delivery of frequencies above 500 MHz, because the standard was designed around tube receivers and mediumwave (or shortwave) antennas (but workarounds[clarification needed] exist). F connectors require slightly more care to properly install the male connectors to the cable than the Belling-Lee type, with the exception of compression or flex type connections.