Video sender

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A video sender is a device for transmitting domestic video signals wirelessly from one room to another, as for example sending the output of a satellite TV decoder located in the lounge, to a television set in the bedroom.

Some video senders also incorporate a return path, to permit infrared remote controls to operate the equipment whose output is being sent.

The equipment requirement is usually either SCART (Europe), composite video or HDMI.

Video senders offer analogue or digital solutions. Analogue versions may be subject to RF interference from other household wireless appliances such as cordless telephones or wireless networks. Where-as digital models utilise standards more familiar with Computer Networks such as Powerline LAN or WiFi.

Analogue solutions have the advantage of low manufacturing costs as the Video and Audio signals are simply modulated onto a carrier at 2.4 GHz . But they have the adverse effect of causing reduced bandwidth to WiFi networks and in some cases WiFi networks can cause picture interference on the video sender signal. To avoid this, some video senders now use the 5.8GHz ISM band, but these are not legal in all the countries that use 2.4GHz ISM for video senders. However, 5.8GHz video senders retain the manufacturing cost advantage. More information can be found in the article on electromagnetic interference at 2.4 GHz. See [1] for explanation and mitigation

Usually there are four FM transmit channels, A, B, C & D, with L & R audio on 6.0MHz and 6.5MHz FM subcarriers added to the composite video baseband. The reverse remote control channel is usually 433.92MHz, fixed, using whatever modulation is on the 34kHz to 45kHz IR remote "carrier". ASK/OOK schemes such as RC5 and RC6 work best over the RF link as the receiver uses a data slicer and AGC designed for ASK/OOK with Manchester encoding.

Digital solutions combine the use of a System on Chip (used for picture and sound encoding/decoding) with a means or launching the signal such as Powerline LAN, WiFi or Ultra-wideband (also known as UWB, ultra-wide band and ultraband) . Whilst Ultra-wideband is generally used for low range applications of typically 10 meters, some manufacturers use proprietary versions of Wi-Fi technology enabling greater ranges to be achieved of typically 80 meters in-building and in excess 2 kilometres clear line-of-sight. Some Digital models maintain an advantage of achieving HD or even Full HD and provide additional connectivity standards such as HDMI as well as analogue connectivity standards such as SCART (Europe) and composite video. The increase in manufacturing cost is reflected in the end user price.