UK Free TV shows the coverage area for a radio transmitter as a coloured overlay (orange for FM, other colours for DAB) on the grey map. We have computed the coverage by combining the terrain with the official radiation pattern. A single click will select the transmitter to view the coverage for a single site, and a double click goes to a page showing full details. Click on the buttons in the right-hand corner of the map to choose from different frequencies (or multiplexes for DAB). 
multiplexes
SDL National