The implementation of a network for terrestrial television is of course dependent on the provision of suitable transmitting antennas radiating from suitable locations. In general, the most appropriate aperture on existing structures is already used by the service for which the mast was built. On the supposition that new structures for most stations will be prohibitively expensive, the re-use of existing antennas is of primary interest. If this is not possible, other alternatives will need to be considered.