Nature 175, 948 - 949 (28 May 1955); doi:10.1038/175948c0

Focusing of Waves in Radio Reception

H. V. GRIFFITHS

(Engineer-in-Charge) B.B.C. Engineering Information Department, Tatsfield Receiving Station, Near Westerham, Kent. Dec. 30.

THE normal maximum field-strength in Kent of the broadcast transmission on 9,700 kc./s. (30.93 metres) from Sofia in undisturbed propagation conditions, and at times of the evening or night when 9.7 Mc./s. is about the optimum working frequency for the transmission path by single refraction in the F-2 layer, is about 1.0–1.5 millivolts per metre (Fig. 1). The aerial power of the Sofia transmitter is believed to be 120 kW. approximately, and the calculated quasi-maximum field-strength in conditions of minimum absorption agrees fairly closely with this field-strength being obtained at the path-distance involved.