FM reception

Press, 18 December 1986, Page 16

FM reception

Sir, — Many people in fringe areas of radio and television reception feel a little frustrated by the varying levels of signals received. While appreciating the advent of FM in Canterbury, I am disappointed at the apparently weaker signal from the concert programme FM transmitter, compared with both of the pop-type stations in Christchurch. Would someone in authority please explain, if this is so, why it has been allowed to happen? — Yours, etc.,

F. J. FORD. Culverden,

December 6, 1986.

[Mr S, A. Mae Diarmid replies for the southern regional engineer, 8.C.N.Z.: “With FM transmissions, listeners may erroneously conclude that loudersounding signals derive from more powerful transmitters or better reception conditions,

whereas the louder sound of one station compared with another is solely due to the different average modulation levels used by these stations. In Christchurch the two commercial “pop-type” stations and the concert station all use quite similarly powered transmitters - and the same transmitting antenna at Sugarloaf. It would be most unusual to find any significant difference in received signal strengths at locations like Culverden. I am confident that the "weaker” signal referred to is simply a signal with a lower average modulation level. Commercial competition causes most stations to opt for compressed programme material, resulting high average modulation and for a “loud” sound to overcome the environmental noise of car travel, business or parties and to have commercial “impact.” The Concert Programme, on the other hand, caters for an audience who wish to hear the maximum dynamic range of symphonic music from the concert hall or compact disc. The use of compression is unacceptable and, essentially, the average modulation is low, even though the peak levels are identical to those of the commercial stations. In Culverden, Concert Programme reception may be unsatisfactory in motor cars and noisy locations, but where the listening environment can be controlled, good reception should be possible.”]