SIGNAL ECHOES.

New Zealand Herald, Volume LXIV, Issue 19736, 8 September 1927, Page 18

SIGNAL ECHOES.

A CAUSE OF DISTORTION. A most interesting phenomenon has recently been noticed in experiments conducted by commercial stations on shortwave telegraphy and telephony. It is found that at certain times of the day observers notice the telephony from distant broadcasting stations working on wave-lengths of less than 30 metres becomes "mushy," and that Morse signals become indecipherable. An extremely interesting .explanation of this phenomenon which has been suggested in Great Britain is being investigated in all parts of the world. The explanation advanced is that the signals from the transmitter reach the distant receiver both ways round the world. As one of these paths is usually longer than the other, a signal which leaves the transmitter at a'given instant will arrive at the receiver at two distinct times, the time required for transmission over the shorter of the two paths being slightly less than that over the longer This means that when only one impulse should be impressed on the receive! two actually reach it. a fraction of a second apart, and in consequence the signal is distorted. Apart from its scientific interest- the phenomenon is of considerable commercial importance, because working under highspeed telegraphic conditions the arrival of the double impulse is likely seriously to interrupt communication. Its probable effect on broadcasting is equnlly important, because it is likely to distort transmissions beyond recognition for considerable periods each day.