Introduction

Television broadcasts are made on different wavebands or groups of channels and your receiving aerial is matched to the appropriate band or group. There are five aerial groups: A, B, C/D, E and W. A television dealer or rental company will advise on which group will serve you best. The size and type of aerial will also affect the quality of signal you receive: if you live close to a main transmitter or relay station, then an aerial with 6-8 elements should work well. If you live at the edge of a transmission coverage area, you may need an aerial with 18 elements in order to pick up a strong signal. Where signal coverage in an area is strong, a low-gain aerial is used, but where it's weaker, a multi-element high-gain aerial strengthens the signal. For people who move home periodically, and take their TV aerial with them, a log-periodic aerial picks up moderate signals if it can be directed at a transmitter.

Aerial Positioning

The position of the aerial is crucial for receiving strong signals: it must be as high as possible and with a clear view to the horizon. This is because VHF television signals travel by line of sight. To judge the direction an aerial should point, look at your neighbours' aerials. In areas where reception is poor - in narrow valleys, where there are lots of tall trees or even in inner cities where there are tower blocks close by - the aerial may have to be mounted on a tall mast or fitted with a booster to improve the signal strength.

Internal Aerials

If you live near a high-power transmitter, you may receive strong enough signals to give you good reception via an indoor aerial, but you may find that passing cars, movement in the room, and, on windy days, trees blowing in the garden or street, will cause interference. You can improve picture quality by moving an indoor aerial as high as possible - to an upstairs bedroom or even to the loft.

Aerial Leads

The lead connecting the aerial to your television set should be a low-loss 75-ohm co-axial cable. Because there is some loss of signal between the aerial and the set, the lead should be kept as short as possible and avoid sharp bends. The connection of the plug at the end of the aerial should be sound.

Repair any damaged connections by stripping the end of the cable and reconnecting it to the plug. Use a sharp knife to split the outer sheath 32mm (1 1/2in) lengthways. Fold or push back the copper wire mesh to clear about 20mm (3/4in) of the hard plastic inner insulation. Using wire strippers, remove 13mm (1/2in) of the inner insulation to reveal the single copper wire at the core. Slide the cap down the cable (note that some cables don't have a cap; instead there is a cable clamp, which screws over the cable). Open the jaws of the cable grip and fit it over the exposed mesh and outer sheath. Make sure there are no 'whiskers' sticking out and the mesh does not touch the inner wire. Squeeze the cable grip with pliers to close the jaws tight onto the sheath. Feed the inner wire into the pin moulding and insert the moulding into the plug body. Then slide the cap up the cable sheath (or replace the cable clamp) and screw it to the plug body.