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Radio Record, Volume I, Issue 2, 29 July 1927, Page 16

Manufacturers who claim that their two and three-valve sets will give continuous reliable reception "from all the inter-State stations’ (says the Melbourne "Argus’’) will be disturbed by a recent investigation carried out by the British Broadcasting Corporation to show the type of receiver needed for first-class reception at various distances from the main British stations. For really effective reception from Daventry, the most powerful of the British stations, it is estimated that for distances up to 30 miles a two-valve set will give satisfaction, For distances between 30 miles and 100 miles, a minimum of three valves is considered necessary, while for effective reception in towns, where field strength is reduced by buildings, four valves are recommended. A minimum of four valves is needed for distances between 100 and 150 miles, and a five-valve set is required for reception of Daventry over greater distances. The real importance of these estimates will be apparent when it is remembered that Daventry uses a power five times as great as the power of the largest Australian broadcasting stations, and transmits on a long wave. For the ordinary British stations, which are about half the power of the Australian stations, :two valves are recommended for reception up to five miles, three valyes for reception from five to 15 miles, and four valves for reception over distances of more than 15 miles. Two Valves Needed. For the relay stations, which are about the same size as the B class stations in Melbourne, two valves are recommended for reception up to two miles from the station, and three valves for reception over distances of between two and three miles. All ‘these estimates assume the use of an aerial not less than 25 feet high and 100 feet long. On the above: figures it will be clear that for reception of Australian stations over distances of 500 miles, about a dozen valves would be required.. British manufacturers, however, freely admit the fact, which is generally disregarded in Australia and América, that the receiver has not yet been built which will give a consistently satisfactory service from a _ broadcasting station working on ordinary broadcasting wavelengths over distances‘ of more than about 70 miles, ‘This distance is the limit of effective reception, irrespective of the power of the broadcasting station. , Fading and Distortion. The limit is determined, not by the sensitivity of the receiver, but partly by the extent to which signal strength is varied, or signals are distorted, by fading effects, and partly by the extent to which transmissions are interrupted by atmospherics. Hoth these factors operate for an average of one night in two throughout the year over distances of more than 70 miles from a broadcasting station, and seriously interfere with ‘the musical value of a programme. It is perfectly true that inter-State stations can be received in Melbourne on two valyes, but for a considerable portion of the time for which the signals are audible, the transmissions are value. less as a sotrce of entertainment,