TV Senders - A Buyers' Guide

Introduction

If you have multiple television sets in or around your home, perhaps in a kitchen, bedroom, or even the garden shed, in addition to the set in your living room, you may want all of them to receive signals from a single conveniently and effectively positioned aerial. This is not altogether easy in the average home however, and although multiple aerials may be a possibility, aerials and cabling are expensive and do little for the aesthetics of your home. A neater and more cost-effective solution may be a wireless A/V ("Audio Video") transmitter (also known as an A/V video or TV "sender") which operates in the same way as a traditional aerial, only on a smaller scale. Indeed an A/V sender can be employed to transmit signals from not only your living room TV, but also your DVD player, "Freeview" box etc., to a receiver positioned anywhere in your home. Signals travel through the air and through intervening walls and ceilings, so no additional cabling is required.

How TV Senders Work

When you connect a wireless A/V transmitter to a TV or any other piece of A/V equipment within your home, that device effectively becomes a broadcaster of audio and video signals. Similarly, if you connect a wireless A/V receiver to another TV (perhaps a TV in a bedroom, for example) that TV becomes capable of receiving and decoding the signals broadcast by the sending device. This means that audio and video signals can be distributed throughout your home, and you can even change TV channels remotely, using a remote control. If you have just a single source of audio, video or both, the only additional piece of equipment that you require is a remote control extender so that you can change channels on a "Freeview" box located in your living room, from a bedroom or elsewhere.

The installation of a TV sender is typically very straightforward. Aerials are usually integrated into the transmitter and receiver units, so it is simply a question of connecting a sending device to a transmitter (typically using a colour coded SCART cable) and a receiving device to a receiver by similar means. Audio and video signals are often transmitted between the sending and receiving devices by means of wideband FM (Frequency Modulation) signals, which can help to minimise interference from other wireless A/V transmitters.

TV Sender Features, Benefits & Considerations

A TV sender can, of course, allow you and your family to watch TV programmes, including "Freeview", on a TV set in a bedroom or elsewhere, without the need to drill holes, or leave trailing cables. A TV sender can also be used for other applications, such as connecting a DVD player to HiFi stereo or other audio system, or connecting a security video camera to a VCR ("Video Cassette Recorder"), again without unsightly runs of cable.

TV senders typically transmit signals in the 2.4GHz frequency band; which is also used by cordless phones, 802.11b and 802.11g based, "WiFi", wireless networking devices, and microwave ovens, and are subject to interference which can degrade picture and sound quality to that of VHS ("Video Home System") or worse. As a solution to this problem, TV senders which transmit in the less crowded 5.8GHz frequency band are becoming increasing available. In any case, it is advisable to position the transmitter and receiver of a TV sender in as open an area as possible, to avoid interference from nearby obstructions.

You should also be aware of the term "line of sight", and its implications for the transmission or reception of audio and video signals. Many TV sender specifications for example, quote the maximum range over which signals can be transmitted, without obstructions of any kind between the transmitter and the receiver. This leads to rather optimistic and unrealistic figures; even a distance of 100' or 150' is unlikely to be available without obstruction in the average home, but these can still be used for comparison purposes and may be more accurate if you wish for example, to transmit audio and video signals to a device in your garden or garden shed. Indeed, some A/V units are specifically designed for outdoor use, with waterproof housings, and the capability of transmitting signals over relatively long distances; over 3,000', or over 4,500' in some cases, when compared to standard domestic TV senders. Do be aware, that once line of sight is removed; that is, the receiver cannot "see" the transmitter, because of intervening obstructions such as walls or doors, the maximum range of a TV sender does start to drop off quite quickly.

If you do find that your TV sender is not performing as well as you might expect (reception is generally poor, or there is a good deal of interference for example) you may need to adjust the frequency or "channel"on which the TV sender is transmitting and receiving. It probably goes without saying that the transmitter and receiver must be on the same channel, but TV senders typically offer multiple channels, so that you can try each to reduce or eliminate interference from other electrical devices. If you find that a domestic electrical device, such as a microwave oven, causes interference on all channels (and this is a distinct possibility, unless you have a higher frequency, 5.8GHz TV sender) you may just need to adopt the habit of not using one device when the other is in operation. Some TV senders feature antennae in the form of high-gain rotating "paddles", which need to be adjusted or aligned to the direction of the wideband FM signal transmitted by the sending device. Bear in mind too, if you have multiple sending devices, that receiving antennae may need to be moved each time you want to receive signals from an new device; an antenna is unlikely to be aligned optimally to receive signals from more than one sending device unless of course, sending devices are in close proximity to each other.

"Wireless" TV senders may be wireless in terms of actually transmitting audio and video signals from one device to another, but more often than not require mains power, and require the sending and receiving devices, which usually require mains power, to be switched on. This means that the solution is never completely wireless. Another restriction that you may come across is that consumer level TV senders are not typically designed for digital TV. RCA or composite connections, along with SCART and S-Video, are all possibilities but very few TV senders are equipped with component video interfaces, suitable for the rigours of HD ("High Definition") TV.

Wireless technology is the most convenient and least expensive solution when it comes to TV senders, but it is not necessarily the best. If you are lucky enough to have coaxial cable (preferably CT100 grade, or above) already laid under your floorboards or carpet, or you are prepared to have it installed in these locations or along your skirting boards, or in special trunking; this may provide a stable, cost-effective, wired TV sender solution. It is really a case of weighing up whether you want an permanent, fixed, system (with the associated expense, and the measures needed to disguise unsightly cabling) or a more flexible, although perhaps slightly inferior wireless TV sender system. Wireless TV sender transmitters and receivers do require their own finite space and cabling, but are generally less obtrusive than fixed systems and offer a greater degree of portability, if you wish to move units between devices.

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