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Spatial Properties of Meteor-Burst Propagation

The experiments described in this paper were carried out to determine the probability of simultaneous reception of meteor-burst signals at different geographic locations (interception) so that the possibility of interference and frequency sharing as well as the suitability of this type propagation to broadcasting may be assessed. Interception tests were conducted at five different sites using transmissions on a 1000-km circuit between Terminal A, near The Hague, The Netherlands, and Terminal B, near Toulon, France. The five monitoring stations were located at Harrogate (Station C) in England, Station D near Paris, Station E near Frieburg in Germany, Station F near Rome, Italy, and Station G, some 35 km from Terminal A. It was found that at Station G the same signal bursts were received as at Terminal A and interception was practically total. At the other four stations, interception was mainly due to the simultaneous occurrence of two meteor trails reflecting waves in different directions. The amount of information intercepted was on the average between 3 and 16 percent, but could occasionally be 100 percent due to sporadic-E reflections. However, the experiments used a frequency of 36 MHz; by operating at 70 MHz or higher interception due to abnormal ionospheric propagation conditions could be virtually eliminated. It is estimated that interference to meteor-burst link from beyond the horizon would be very inefficient since the power ratio at 40 MHz is about 25 to 1 in favor of the link. At higher frequencies the advantage for the link would be much greater. The results of the interception tests show that meteor-burst systems can be used for broadcasting provided that three separate antenna systems are employed to cover ranges up to 2000 km and to repeat the message continuously from one to several minutes to achieve a high probability of reception. Frequency sharing between several meteor-burst links operating in the same area also appears to be feasible with frequencies high enough to eliminate ionospheric scatter and sporadic-E layer reflections.