There are many places in the UK where there are more than one transmitter to point TV Aerials at in which to get a good reception and picture. Take Lancaster in the United Kingdom, here is a city where you will see some aerials pointing one way in a horizontal position and then aerials in a vertical position pointing in the opposite direction. Ever wondered why and which would be the best set up to choose? Well firstly it would be useful to discover why the aerials are pointing to two separate locations and also why some are in the vertical position and others in horizontal. The reason is that as an Aerial Fitters in Lancaster you’d be faced with this situation is because it is possible to pick up both the main transmitter broadcast from winter hill near Bolton, and also the relay transmitter just outside of Lancaster.
When digital aerials point at the main transmitter for the region they will be positioned horizontal because of the way that the digital signal is being transmitted, but when the aerials are pointing towards a relay transmitter then they will all be positioned vertical. The reasons for that are to stop a repeating of the same signals when in an area that can pick up both the main and relay transmitters. If that where to happen there would be a situation of some TV’s picking up a strong signal and others a weak one, also there would be ghosting on the screen. This still used to happen in some areas when the TV signals were broadcast in analogue not digital.
In Lancaster, depending where about in the area the aerial is situated, it can pick up a good enough signal from winter hill, which is preferable than the relay because it picks up more channel choice from the main over the relay which always broadcasts less channels. If an aerial is required to be installed in the loft, then it would be advisable to have it pointing towards the relay transmitter because it will have a stronger and clearer signal, and loft installed aerials will always receive less of the signal than if they are mounted out side on the house.
A little bit further towards the coast in Morecambe or Heysham the signal from winter hill although further away is still stronger and an average signal strength is around 60-65db with good quality. Here it is possible to put an aerial in the loft pointing to winter hill, but it may need to be amplified if it is being split.
As stated before the way the aerial is positioned determines which signal it will pick up, since the signal broadcast is either vertical polarization or a horizontal polarization. Even if you were to point the aerial at the wrong transmitter the way the aerial is positioned will favour the other one.