Reduction of mush-area distortion in common-frequency m.f. transmitter networks

The present crowding of the medium-wave band has made it necessary for several transmitters which broadcast the same programme to operate at a common carrier frequency. Reception is impaired by ground-wave interference between pairs of such transmitters in regions where the ratio of their field strengths is less than about 10 dB. At night, mutual interference is caused by sky-wave signals from other transmitters in the group. The results of laboratory tests are given which assess the improvement to daytime reception that would result if the times of arrival of the two modulations were equated in these regions. The practicability of implementing such an arrangement is discussed and the preliminary results of a field trial are given.