RF modulator
From Wikipedia, the free encyclopedia
An RF modulator (for radio frequency modulator) is a device that takes a baseband input signal and outputs a radio frequency-modulated signal.
This is often a preliminary step in transmitting signals, either across open air via an antenna or transmission to another device such as a television.
[edit] TV Modulators
In order to display picture information on a television, the data must be modulated, or conditioned, to the format that the television expects. This usually means combining the data with a carrier wave at a standardized frequency.
TV Modulators take the audio and video signal from a composite video, RGB, YUV or internal source, and generates a PAL or NTSC broadcast signal that can be fed into a television's aerial/coaxial connector.
Internal RF Modulators are commonly found in VCRs, and older videogame consoles such as the Atari 2600, NES, or N64. During the 1980s and early 90s, it was common for systems that did not have internal RF modulators to provide external units that connected to the antenna jacks of a television; however, as television designs gained composite, S-Video, and component video jacks, manufacturers stopped including the modulators as technology advanced. RF modulators are now largely a third-party product, purchased primarily to run newer equipment such as DVD players on old televisions.
RF modulators produce a relatively poor picture, as image quality is lost during both the Modulation from the source device, and Demodulation in the television.
For this reason, many newer televisions provide RGB, composite video or S-Video inputs, which offer superior image quality and bypass RF modulation altogether. However, the aerial connector is standard on all TV sets, even very old ones. For this reason, stand-alone RF units are available, for connecting video devices using newer inputs to any TV set using an aerial connector. RF modulators generally output on channel 3 or 4, although the Atari consoles offer channels 2 & 3.
Different RF modulators that are audio only, and output on FM Radio frequencies are also used in car audio to connect such devices as add-on CD changers and video systems. These FM modulators also suffer from loss of quality and interference issues.
An example of RF Modulation in use can be found at herenl:HF-modulator
