Peak Field Strength of Atmospherics Due to Local Thunderstorms at 150 Megacycles

Atmospherics in the 150-megacycle frequency range were investigated with a broad-band receiver and cathode-ray-tube scanning technique. The results are of general interest in connection with the problems of atmospheric noise interference on various types of ultra-short-wave radio-communication channels. Some of the conclusions are: (1) The peak intensity of disturbances varies 20 decibels between different storms at the same distance. (2) The inverse distance relation is a good approximation for the calculation of the variation of peak disturbance with distance, for any distance and height of receiving antenna likely to be used in a commercial system. (3) The use of high instead of low receiving antennas increases the signal-to-disturbance ratio almost directly with height for storms within 10 miles. (4) The durations of some of the narrower peaks in any particular lightning discharge are at least as short as a few microseconds. (5) The maximum peak field strength of disturbances for a storm 1 mile distance is 85 decibels and for a storm 10 miles distant is 65 decibels above 1 microvolt per meter at a frequency of 150 megacycles with a band width of 1.5 megacycles. The technique of observations provided a visual indication of the noise interference which might be expected with television signals. It appears that with signal field strengths, such as might reasonably be expected, atmospherics due to thunderstorms will be noticeable for ultra-short-wave television transmission at times when storms are in progress near the point of reception.