RF modulator

An RF modulator (or radio abundance modulator) is a accessory that takes a baseband ascribe arresting and outputs a radio frequency-modulated signal.

This is generally a basic footfall in transmitting signals, either beyond accessible air via an antenna or manual to addition accessory such as a television.

Design

In adjustment to affectation abstracts advice on aboriginal analog televisions, the abstracts accept to be modulated, or conditioned, to the architecture that the television expects. TVs were advised to alone acquire signals through the aeriform connector: signals arise at a TV station, are transmitted over the air, and are again accustomed by an antenna and fed into the TV. Thus, added equipment, such as a VCR, DVD player, or video bold console, which wishes to forward a arresting to such an old TV accept to carbon this process, in aftereffect "faking" an over-the-air signal. Technically, this usually agency accumulation the abstracts with a carrier beachcomber at a affiliated frequency.

RF modulators aftermath a almost poor picture, as angel superior is absent during both the accentuation from the antecedent device, and the demodulation in the television, but the aeriform adapter is accepted on all TV sets, even actual old ones. Since after television designs cover composite, S-Video, and basic video jacks, which skip the accentuation and demodulation steps, modulators are no best included as accepted equipment, and RF modulators are now abundantly a third-party product, purchased primarily to run newer accessories such as DVD players on old televisions.

An RF modulator yield the audio and video arresting from a PAL or NTSC blended video, RGB, YUV or added blended AV source, and generates a advertisement RF arresting that can be fed into a television's aerial/coaxial connector.

Multi-channel RF modulators are frequently acclimated in home audio/video distribution. These accessories accept assorted audio and video inputs and one RF output. Audio/video outputs from antecedent accessories such as a DVD player, VCR, or DSS receiver are affiliated to the audio/video inputs on the modulator. The modulator is again programmed to advertisement the signals on a assertive frequency. That RF advertisement is again accustomed by the affiliated TV. When the TV is acquainted to the programmed channel, the audio/video arresting of the antecedent accessory is accessed. RF accentuation can become difficult in a CATV system. High pass, low pass, and cleft filters accept to be acclimated to block assertive frequencies, or channels, so that the modulator can advertisement the audio/video arresting of the antecedent accessory on that channel.

Uses

Internal RF modulators are frequently begin in VCRs, in earlier video bold consoles such as the Atari 2600, NES, or Sega Master System, and in earlier home computers such as the Commodore 64, Atari 800, and Sinclair Spectrum.

During the 1980s and aboriginal '90s, it was accepted for video bold systems that did not accept centralized RF modulators to accommodate alien units that affiliated to the antenna jacks of a television. One acumen for this is that a accessory which outputs an RF arresting have to in accepted be certified by authoritative authorities—in the US, the FCC—and appropriately by accepting an alien RF modulator, alone the modulator itself bare to be certified, rather than the absolute video bold system.

TV modulators about affection analog passthrough, acceptation that they yield ascribe both from the accessory and from the accepted antenna input, and the antenna ascribe "passes through" to the TV, with accessory admittance accident due to the added device. In some cases the antenna ascribe is consistently anesthetized through, while in added cases the antenna ascribe is angry off if the accessory is outputting a signal, and alone the accessory arresting is beatific onward, to abate interference.

In North America, RF modulators about achievement on approach 3 or 4 (VHF), which may be selectable, although the Atari consoles action channels 2 and 3. In Europe accepted modulators use approach 36 (UHF) by absence but are usually tunable over allotment or all of the UHF band.

stereo

Modulating a TV arresting with stereo complete is almost circuitous and a lot of bargain home TV modulators aftermath a arresting with monaural audio. Even some units that accept two audio inputs artlessly amalgamate the larboard and appropriate audio channels into one address audio signal. Some acclimated on actual aboriginal home computers had no complete adequacy at all. A lot of cheaper modulators (i.e. not advised for able use) abridgement balance sideband filtering.

Audio RF modulators are acclimated in low-end car audio to add accessories like CD changers after acute dashboard accouterments upgrades. For example, a carriageable CD player's headphone jack is affiliated to the modulator, which outputs a low-power FM radio signal, which plays through the car radio. Car FM modulators ache from accident of superior and arrest issues.