Interpreting the U.K. and R.O.I. TV coverage maps

The reception predictions presented have been calculated using public-domain information about analogue and digital UHF BBC, ITC, Channel 5 and Restricted Service Licence stations (in the U.K.) and RTÉ 1, RTÉ 2, TV 3 and TG 4 stations and deflectors (in R.O.I.). Although care has been taken to maintain this information as accurately as possible, and the methods of calculation have been examined and tested, it must be borne in mind that vital additional factors need to be considered when interpreting the results. Consequently, all results should be used only as a rough indication as to which transmitters might be available at a specified location. Where the predictions show a choice of transmitters giving similar field strengths, it is usually worth considering the closest first.

Full details of the calculations will be written up later. For the present, please regard all results as preliminary and experimental. Several assumptions have been made in the current methods, of which we consider the following three to be markedly unsafe:
 

• For the U.K. stations, but not for those of R.O.I., no account has been taken of the directional radiation patterns of some transmitters (e.g. coastal restrictions).
• It has, for the present, been assumed that all U.K. radiators are omnidirectional. This is certainly unrepresentative of many cases, a good example being the Channel 5 coverage from Croydon which is in reality heavily reduced to the South and South-East to prevent interference with French stations. This is being actively researched at the present time.
• For points in Ireland, no account has been taken of obstacles in the intervening terrain (e.g. mountains and valleys).
• This is being actively researched at the present time.
• No account has been taken of sources of interference (e.g. strong adjacents).
• This is particularly relevant to the reception of digital signals.

The "antenna suggestions" should also be regarded as very tentative. They are based upon what would be required to provide a typical receiver with the correct input signal given the field strength calculated as described above assuming a minimum height of 10 m above ground. Where an "amplified extra hi-gain" system is suggested, the minimum would probably be a good multi-director Yagi array with a low-noise masthead amplifier. It can readily be shown that many areas marked as needing very high-gain systems enjoy adequate reception with quite modest arrays, and of course vice versa.

In cases where a transmitter's digital multiplexes have differing effective radiated powers (ERPs) or antenna heights the worst case is used in calculations.