- RF modulator
An RF modulator (for
radio frequency modulator ) is a device that takes abaseband input signal and outputs aradio 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 .TV modulators
In order to display picture information on a pre-digital
television , the data must be modulated, or conditioned, to the format that the television expects. This usually means combining the data with acarrier wave at a standardized frequency.TV modulators take the audio and video signal from a
composite video ,RGB ,YUV or internal source, and generates aPAL orNTSC broadcast signal that can be fed into atelevision 's aerial/coaxial connector.Internal RF modulators are commonly found in
VCR s, and older video game consoles such as theAtari 2600 , NES, orSega Genesis . During the 1980s and early 90s, it was common for video game systems that did not have internal RF modulators to provide external units that connected to the antenna jacks of a television. RF modulators produce a relatively poor picture, as image quality is lost during both the modulation from the source device, and the demodulation in the television, but the aerial connector is standard on all TV sets, even very old ones. Since later television designs include composite,S-Video , andcomponent video jacks, game manufacturers have stopped including modulators. RF modulators are now largely a third-party product, purchased primarily to run newer equipment such asDVD player s on old televisions.RF modulators generally output on channel 3 or 4, although the
Atari consoles offer channels 2 & 3. In Europe standard modulators use channel 36 (UHF).Modulating a TV signal with stereo sound is relatively complex and most low-cost home TV modulators produce a signal with monaural audio. Even some units that have two audio inputs simply combine the left and right audio channels into one mono audio signal.
Multi-channel video modulators
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 audio/video signal of the source device is accessed. RF modulation can become difficult in a 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.
Audio modulators
Audio RF modulators are used in low-end car audio to add devices like CD changers without requiring dashboard hardware upgrades. For example, a portable CD player's headphone jack is connected to the modulator, which outputs a low-power
FM radio signal, which plays through the car radio. CarFM modulators suffer from loss of quality and interference issues.
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