Data Sheet

#53 TV and radio reception when touring

#53 #53 TV and radio reception when touring
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2: Receiving a good TV signal

Receiving a good TV signal

The leisure industry is well served with TV aerials - most new caravans and motorhomes have had one as standard equipment for many years.

Initially most of these were omnidirectional, meaning they picked up signals equally from all directions and so needed no adjustment. In the days of analogue television this could lead to a ghostly looking picture if the aerial picked up a signal directly and then the same signal was reflected from a nearby object a tiny fraction of a second later.

The gradual switch over to digital television with its better picture quality but initially low transmission power encouraged caravan and motorhome manufacturers to fit directional aerials for their ability to shut out unwanted signals and deliver a better quality signal.

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The Status 315 omnidirectional TV aerial is a common sight on older caravans and motorhomes

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Directional aerials such as this one from Status 530 have largely replaced the omnidirectional ones

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Where a TV aerial is not a standard fit it can be quite easy to use something like this self-adhesive unit from Maxview

With one of these you not only need to know which direction to aim for but also whether the aerial's elements need to be vertical or horizontal, according to the polarisation of the signal. To help with this the Club has produced a handy guide called TV Aerial Direction and Advice covering the Club Sites (see information panel).

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A signal strength meter is a big help in maximising the signal from the aerial

Look at the position and angle of aerials on buildings, other caravans and motorhomes on site and see if you can match them.

Without such a guide you could use one of the many smartphone apps such as Antenna Aligner or Freepoint that indicate where to point the aerial for best reception. Even then the "all or nothing" nature of digital signals is such that a signal strength meter of some form is really the best way to get a good signal.

If you are in a strong signal area you may get away with an indoor aerial but these tend to be ineffective inside caravans and motorhomes with aluminium sides, as the aluminium blocks the signal.

One of the issues with terrestrial TV when touring is the need to retune your TV as you move from one area to another. This is because adjacent transmitters use different frequencies so as not to interfere with each other.

Retuning is not a big issue with modern TVs as most will find and store stations automatically, but only once you have found the menu item that tells them to do so.

Digital transmissions can carry lots of signals on a single frequency. The process that makes this possible is known as multiplexing or muxing and the resulting signal is referred to as a MUX. The signal can include multiple TV and radio channels, text services and electronic programme guide information.

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This aerial has been turned to the vertical position to pick up a relay station

The full Freeview service in the UK uses six multiplexes. Three of these are designated for Public Service Broadcasts (PSB) and include the main BBC and ITV channels. The remaining three are designated Commercial (COM) and carry all the other channels.

In addition to the primary transmitting masts, there are a large number of smaller ones, known as relay stations, designed to provide cover in those areas where the primary masts do not reach, perhaps because of terrain issues.

While the primary transmitters carry all six multiplexes by default, it is up to the operators of the relay transmitters to decide which, if any, of the relay stations will do so. So far none has done so.

Another interesting point about relay stations is that the signals from them are normally vertically polarised to avoid interference with the primary transmitters, which usually have horizontal polarisation.

Satellite broadcasts

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Just some of the many satellites visible from the UK. The satellite highlighted in yellow is Astra 2, which carries many UK channels

Satellite-based broadcasts have revolutionised TV and radio reception by making it available throughout the UK. To pack in the huge amount of data needed to make satellite broadcasting worthwhile, extremely high frequencies are used, typically in the range 10,000 to 13,000 MHz. Reception requires a suitable dish, equipped with a Low-Noise Block downconverter (LNB) and pointed accurately at the satellite.