Editing RF modulator (section)

== Uses ==
[[File:Cable headend modulator.jpg|thumb|Cable TV Agile Modulator]]

RF modulators are commonly integrated into VCRs, in video game consoles up to and including the [[Fourth generation of video game consoles|fourth generation]], and in 8- and 16-bit [[home computer]]s.

Some systems were supplied with an external modulator unit that connected to both the system and to the antenna jacks of a television. One reason for this is that a device which outputs an RF signal must in general be certified by regulatory authorities—such as the U.S. [[Federal Communications Commission]] (FCC) — and thus by having an external RF modulator, only the modulator itself needed to be certified, rather than the entire video game system. One example was the [[Sup'R'Mod]], designed for the [[Apple II]].{{citation needed|date=May 2012}}

RF modulators may also be used to take the audio and video signal from a [[PAL]] or [[NTSC]] [[composite video]], [[RGB color model|RGB]], [[YUV]] or other composite AV source, and generate a broadcast RF signal that can be fed into a television's aerial/coaxial connector.

Multi-channel RF modulators are commonly used in home audio/video distribution. These devices have multiple audio and video inputs and one RF output. Audio/video outputs from source devices such as a DVD player, VCR, or DSS receiver are connected to the audio/video inputs on the modulator. The modulator is then programmed to broadcast the signals on a certain frequency. That RF broadcast is then received by the connected TV. When the TV is tuned to the programmed channel, the video and audio signal of the source device is accessed. RF modulation can become difficult in a [[Cable television|CATV]] system. High pass, low pass, and notch filters must be used to block certain frequencies, or channels, so that the modulator can broadcast the audio/video signal of the source device on that channel.

"Professional" modulators such as those used in the CATV industry generally include vestigial sideband filtering which is generally absent on "consumer" grade modulators.