A CURIOUS PHENOMENON

Radio Record, Volume I, Issue 26, 13 January 1928, Page 4

A CURIOUS PHENOMENON

‘Nature’? of October 15, 1927, says the experiments being made with short radio waves all over the world are giving most astonishing results. In the October number of ‘‘Experimental Wireless," the Radio Research Board refers to results obtained by E. Quack, published in two German technical papers. Oscillographic records have been obtained at Geltow, near Berlin, of signals sent from Rio de Janeiro. Each signal is accompanied by an ‘echo’ signal, caused, most probably, by waves which have travelled round the earth in the opposite direction to the direct signal. This is most curious, because the beam transmitter is not only directional, but also works with a reflector. Further experiments carried out recently show that several signals are received at definite equal intervals after the first signal. As the interval of time between the first direct signal and these additional signals is always a multiple of 0.187 of a second, it looks as if the waves, after causing the first signal, travelled completely round the world several times, recording signals as they assed the receiver. For waves lying etween 14 and 34 metres, donble signals have been observed. It has also been noticed that double signals occur most commonly when the great circle on which the receiver and tranamittgr lie is in twilight, On the other hand, the "echo" signals caused by waves travelling round the world in the opposite direction to the direct signal are often noticed in the daytime. The attenuation of the signals after encircling the earth several times is not great, and it is concluded that many more encirclings occur hefore the waves subside. In practical work, methods have to he devised to eliminate the disturbances caused by these multiple signals, but their systematic study should be a great help in elucidating the phenomena of short-wave propagation, ; .