What Is an RF Antenna Input?

A radio frequency (RF) signal is an electrical signal emitted as a radio wave. It travels from the broadcasting antenna to the receiving antenna. Different channels carry the signal at different frequencies. Depending on conditions, the signal can be received as far as 80 miles from the broadcast antenna. An RF signal can also be carried on wires that have been configured appropriately, either from a nearby broadcast antenna or as part of a cable TV distribution system serving an area ranging from a building to a city.

The most common RF input resembles a short, thick bolt about one-quarter inch in diameter and one-quarter inch long. The cable cord screws into the bolt. Older television sets may have two screws side by side, designed to attach wires from a cable called a twin lead. There is an electrical difference between the two forms of connector. An adapter may be required to attach twin lead wires to a round RF input or vice versa. The adapters are inexpensive and widely available.

A television image encoded as an RF signal contains audio and video, both of which are decoded using a tuner. The key difference between a monitor and a television set is that a monitor cannot process an RF signal directly. Most televisions, VCRs, and cable TV boxes let you output the decoded audio and video signal to other devices. Separating the video and audio signals gives better quality than the integrated RF signal; S-video, component video, and HDMI outputs offer higher quality than RF. For a computer to process RF signals it must have a video card equipped with an RF input plug, as well as other hardware and channel-selecting software.

Using an RF signal to carry audio and video from one device to another is an option of last resort, as it is always the lowest-quality option. However, with older television sets and VCRs, or in complex setups, RF may the only option available. Most VCRs, legacy game consoles, satellite receivers, and cable descramblers can accommodate an RF signal, typically on channel 3. External RF modulators are available to generate an RF signal from the video and audio outputs widely used on computers and audio-video devices.

RF signals are used for FM radio signals and Wi-Fi computer networks. FM radios and audio/video receivers may have an RF input for the radio antenna, or a connection for a cable system carrying FM radio signals. Wi-Fi antennas usually connect directly to the wireless transmitter.