• all main transmitters send 'horizontally polarised' signals. Your aerial therefore has to be 'horizontally polarised' (mounted) to work properly;
• but nearly all relay transmitters send 'vertically polarised' signals. Your aerial will probably have to be ‘vertically polarised' (mounted) to work properly.

All the aerial types we describe below can be horizontally or vertically mounted. In some extreme cases, one aerial may not be enough to get all channels clearly. So you may need two aerials, each adjusted to pick up different stations. You will also need two leads and a switch.

Most aerials are of the 'Yagi' type. The more rods or 'elements' it has, the better it can pick up the TV signal. A 'Yagi' aerial with between 10 and 18 elements is usually enough for good reception. (This example is horizontally polarised)

If you live in a fringe or low-lying area surrounded by higher ground, you may need a 'High Gain' version of the 'Yagi' aerial, with its characteristic X shaped elements. This can reduce ghosting or double images. (This example is horizontally polarised).

'Grid' aerials are especially good for ghosting (double images on your screen) when the source of the reflected signal is behind you. When these can be horizontally polarised (i.e. all main transmitters and a few relays) they are best for locations like estuaries which suffer from tidal fading. (This example is horizontally polarised).

Channels, aerial groups and colour codes
Aerials are often grouped in letter or colour codes according to the channel ranges they’re designed to pick up. A coloured plastic bung used in the construction indicates the aerial’s group. Some manufacturers put the full information on a plate and use a black bung instead.