CAN WIRELESS TELEGRAPHIC MESSAGES BE INTERCEPTED?

Otago Daily Times, Issue 11507, 21 August 1899, Page 8

CAN WIRELESS TELEGRAPHIC MESSAGES BE INTERCEPTED?

As much disciission has been provoked by the' possibility of wireless telegraphic messages being intercepted during their flight through the,air by.persons other,than those for whom they were intended, the article in the current " Windsor" upon " Signor Marconi and Wireless Telegraphy" will be read with timely interest. Regarding this point, Mr Cleveland Moffet, the writer of the article, says:-■"ln-the first place it is evident-that-generals and admirals, as well as private individuals, could always protect themselves by sending their despatches in cipher. Then, during active military operations, despatches could often be kept within a friendly radius.by lowering tho wire on the mast until its transmitting power came iwithin that., radius. Marconi realises, of course, the, desirability, of, being able in certain cases, to transmit messages in one and only one direction. To this end he has conducted a special series of experiments with different sending apparatus from that already' described! He uses no wire here but a Ttighi" oscillator placed at the focus of a. parabolic copper reflector two or three feet in diameter. The waves sent out by this oscillator are quite different from the others, being only about 2ft long instead of 300 ft or 400 ft, and the results," up to the present, are. less important than those obtained ■ with the pendant wire. Still, in trials on the Salisbury Plain, Marconi and his assistants sent messages perfectly in this way over a distance of a mile and three-quarters, and were- able to direct these messages at will by aiming the reflector in one direction or another, 'it appears that these Hertzian waves, though invisible, may be concentrated by parabolic reflectors into parallel, .beams and projected in narrow lines just as a bull's-eye lantern projects beams of light. And it .was found that a very slight shifting of tfie refleutov would stop the messages at the receiving end. Iv other words, ' juiless th,e Hertzian beams fell directly on the receiver there was an end of all communication. Besides the possibility of directing the waves with reflectors, Marconi is now engaged in most promising experiments in syntony, which I may describe us the electrical tuning of a particular transmitter' to a particular receiver, so that the1 latter will respond to the former, and no other. That, of course, is a possibility in the future, but it bids fair soon to be realise^'. There are even some who maintain thjfc they may be produced as many separate sets of transmitters and receivers only capable of working together as there are- separate sets of Yale locks and keys. In that event, any two private individuals may communicate freely without fear.of being misunderstood by others."

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