Back

Terrestrial aerials

Even if you have an aerial it might not be good enough for digital so you might be looking to improve or upgrade it. To find out your likely signal, use the calculator at http://www.wolfbane.com/cgi-bin/tvd.exe?. This takes into account distance from the transmitter and any intervening high ground. It advises whether you might need a masthead amplifier. This is fitted on the mast no more than a metre from the aerial. The output cable from this amp goes into the house and then to a power supply unit which passes the signal through.

Different frequencies (channel numbers) are used in different parts of the country. There are four groups called A, B, C and D. You need to find out what group your nearest transmitter uses. Again Wolfbane will help. You can buy wideband aerials that cover all four groups. It is best to buy a single band one, as this will give you a slightly better signal. There is no such thing as a 'digital aerial'. It means either a wideband one, or one that gives a better signal in poor reception areas.

One further complication is polarisation. In very poor reception areas there are sometimes local low-powered transmitters to cover areas in the shadow of hills. To avoid interference, these will be on a different group from the main local transmitter and send out waves that go up and down instead of from side to side. The aerial will need to be turned so that the metal bars are vertical.

You will need a distribution amplifier in the house to split the signal if you have more than one TV or digital box. It will also boost the signal to compensate for losses in cable runs and connectors. Amps with up to eight outputs are very reasonably priced. If the power supply and distribution amplifier are in your loft you will need to provide a mains power supply. Alternatively you could install them in a spare room or in a cupboard that has a nearby mains socket.

You need a mast that reaches as high as is safe. Remember that the more free height there is above the topmost bracket the more leverage the wind will have on the mounting brackets. You can mount onto a chimney using brackets and wires. I prefer a more substantial installation on a pair of brackets bolted to the gable end of the house. Assemble the aerials and amplifier on the mast before you lift it into position.

The wolfbane site also gives you a compass bearing to aim your aerial at the transmitter. You need a compass of course, but a simple walker's one will do. Slacken the holding bolts and rotate the aerial mast to the rough position given by your compass. Then plug in a Freeview box and get a companion to tell you when the signal is best so you can do the fine adjustment. Most Freeview boxes will show you the signal strength. If yours doesn't then borrow one that does. Don't forget to tighten the bolts holding the mast!

To get an idea of prices and appearance of the equipment look at www.tvaerials.com.

	Back

(C) Peter Scott 2009

Last edit 26 December 2015