RADIO'S SHARP EARS

Evening Post, Volume CVI, Issue 90, 13 October 1923, Page 21

RADIO'S SHARP EARS

WONDERFUL DISTANCE RECORDS.

Last- Saturday's cable message from Au*£r*)i," sia-tiag that Mr. C. D. w.'-Orarcaa, ot Strathfield, N.S.W., had communicated with Mr. F. D. Bell, of Shag Valley, Palmevston South, using only .0037 watt', sounded too good to be true, notwithstanding that both these experimenters an d others in Australia and New Zealand have been-doing wonders with small' The "Otago Daily Times'' inquired into the accuracy of the report,, and found that Mr. Bell was able to hear .Mr. M'Clurcan briefly when the power; ; used was i .04 watt (near enough to .037 watt), but was unable to get him again. We. have no details yet as to what sort of equipment was used for reception, but no doubt it was the most sensitive available in Mr. Bell's extensive array. The extraordinary significance of catching, even momentarily, such a weak transmission across 1200 miles of sea can be judged from the fact that SCO miles for a swatt transmitter is regarded as extraordt inarily good, and as attainable only with a radiating system of the highest efficiency. Mr. S. M. Newman, a 'Victorian amateur, using a transmitter which except for the high tension generatorand the milliammeter is home-made, has results of that character to his credit, and as long ago as last April his 0. "W. Morse signals and speech, addressed to a Sydney.. amateur,. were heard by Mr. Bell, 1400 miles away, and afterwards the two stations got into systematic communication, Mr. Newman using six watts. Mr. Newman appears to work at 400 meters; Mr. Bell at various lengths from 155 to 270. A GOOD PABT OF THE WORLD! There may be something especially favourable to long-distance low-power work in this part of the world, for nothing of the same kind appears to be recorded either at Home or in America. A feature of American wireless literature is the constant recording cf "DX," as long-distance reception is called in radio jargon,. and amateurs are quite proud of picking up 500 watt broadcast I across the width of the. continent, let alone low-power amateurs. Yet New Zealand amateurs have heard American amateurs by the ' dozen, and not only those on the Pacific Coast, but in States ' all over the union, including New York, j On (jne Sunday evening Mr. Bell heard j 17 stations, scattered across the whole width of America, and got their call signs. These results are incomparably ■brighter than Australian. amateurs have been able to claim. The difference is probably due to atmospheric differences rather than to equipment or operatorship. . . .VALVES IN COMMERCIAL WORK. It is remarkable that the amateur experts have been able to_ make performance which seem completely to outshine commercial Morse work, with its much higher power. But an essential difference is that most commercial work except that of the high-power stations, is done with spark transmitters, the waves of which seem to die out much sooner than the sustained waves-of the valve transmitter. The superiority of continuous waves, especially of the easily controlled and pure, oscillation of the valve transmitter, is steadily winning in the radio field, and it will not be j long before spark stations, will disap- ' pear. They are more troublesome, far more costly to maintain and run, and less effiicent; and they cause more interference than valve transmitters. ' The relative efficiency of valve and spark in comercial work was recently demonstrated by a test carried out by the United States navy, between a. 100 kilowatt spark set and a 6 kilowatt valve transmitter. . The listeners declared that the valve signals were read more easily than the spark signals. In another test, a 6 kilowatt valve set gave better results than a high-power arc. Highly gratifying results were also secured with a valve transmitter installed on the battleship Wyoming. The naval regort states that some results were unexpected, such as ability to receive on the same vessel numerous broadcasting stations transmitting on about 400 metres, while the ship's valve transmitter was supplying 36 amperes to the main aerial on a wave-length of 507 metres. This condition allows duplex communication, which has actually been put in practice on' the Wyoming, and will be further developed on the Colorado and West Virginia.