WIRELESS ECHOES.

Matamata Record, Volume XI, Issue 933, 2 July 1928, Page 5

WIRELESS ECHOES.

- Not many years ago the small dl tance to which radio signals could be sent was a serious limitation com mercial application. The difficu y was overcome in relative y. time by means of receiving mstraments of greater sensitivity transmitting stations of higher pow er so that now distance is no limi tion. Interesting evidence that developments of this character may overshoot themselves is (says the El rical World) indicated by recent e periments; between radio stations in Germany and the United States. It had been noticed for some time that in certain;, stations signals were repeating themselves at short-time intervals, with a consequent blurring and confusion of subsequent signals, thus lowering the purity of the received message. The experiments indicated were carried out to investigate the cause of this repetition. Oscillographic records were taken, which permitted an exact knowledge of the amplitude of the original and subsequent signals, and the time interval between them. In some cases triple signals were found. The observation have pointed to the very interesting conclusion) that the .repeated signals may be due either to the passage of the original. signal around the earth the second time, or to its passage in the reverse direction j from the sending station, or to both parts of propagation. The time intervals are of the order of tenths of a second, and the velocities of propagation indicated are of the same order of magnitude, although somewhat less than the velocity of light. An additional indication from the experiments ii that a directional antenna may give out a reverse signal of considerable intensity which, on the opposite side of the earth has a fraction of the intensity of the direct signal. Investigation and study are proceeding with,the purpose of finding a method to eliminate these repeated signals of over-zealous transmitting systems. So far no remedy is proposed, but one may be confidently expected. , • • ■ •