ABSTRACTS OF TECHNICAL ARTICLES 389 



ized and data are presented to show the performance of the instrument 

 which is in fair agreement with the theory. 



Peak Field Strength of Atmospherics Due to Local Thunderstorms at 

 150 Megacycles} J. P. Schafer and W. M. Goodall. Atmospherics 

 in the 150-megacycIe 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-com- 

 munication 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 re- 

 ceiving 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 micro- 

 seconds. (5) The maximum peak field strength of disturbances for a 

 storm one mile distant is 85 decibels and for a storm ten 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. 



Metal Horns as Directive Receivers of Ultra-Short Waves} G. C. 

 SouTHWORTH and A. P. King. The paper describes some experiments 

 made to determine the directive properties of metal pipes and horns 

 when used as receivers of electromagnetic waves. The experiments 

 were of two kinds. One consisted of measurements of received power, 

 with and without the horn in place, and the other of the determination 

 of the directional patterns of the horns in two perpendicular planes. 

 The results indicate that electromagnetic horns of this kind provide a 

 simple and convenient way of obtaining effective power ratios of a 

 hundred or more (20 decibels). The effects of varying the several 

 horn parameters are investigated. It is shown that there is an 



^Proc. I. R. E., March 1939. 

 * Proc. I. R. E., February 1939. 



