EMC at transmitter sites

EMC at transmitter sites is, to a certain extent, quite a different problem to that encountered in other situations; this is mainly because the broadcaster intends to radiate electromagnetic waves and, generally, problems arise as a result of intended radiation. This is especially true for long wave (LF) and medium wave (MF) transmissions where ground wave propagation is used, and for short wave (HF) transmissions where, though the mode of propagation is sky wave, the ground is an integral part of the operation of the antenna. At VHF and UHF, as transmissions are `free space´ using directional antennas, usually located some distance from the ground up a mast or tower, problems at ground level are less severe. However, the field strengths are still likely to be higher than those encountered in a `normal´ environment. Broadcasters have been operating successfully for many years in electromagnetic environments that are harsher than those laid down in the various generic standards. Until suitable product standards are completed, confusion over testing will remain and the EMC Directive will be seen as having done little for the broadcaster except introduce a raft of extra legislation