RADIO NOTES.

Waikato Independent, Volume XXIX, Issue 3157, 7 November 1929, Page 3

RADIO NOTES.

UNITED STATES LEADS. From a bulletin recently issued by the United States Department of Commerce it has been possible to compile a list of the receiving sets estimated to be in use in various countries of the world; 129 countries have been listed, from Ethiopia with two sets to U.S.A. with nearly ten million. The leading 25 countries as listed hereunder: U.S.A. .. • • 9,640,348 Great Britain .. . • 2,511,736 Germany . . .. 2,350,000 France .. • • 1,250,000 Japan . . • • 550,000 Argentine .. • • 530,500 Sweden . • • • 371,000 Austria ‘ . . • • 325,000 Australia . . • • 304,000 Russia . • ■ • 250,000 Italy. .... 250,000 Brazil • ■ • • 250,000 Czocho-Slovakia .. .. 250,000 Canada . . • • 230,000 Denmark . . . • 215,000 Netherlands .. 150,000 Union of S. Africa .. 130,000 Finland .. .. 127,000 Switzerland .. 75,000 Norway . . • • 70,000 Belgium . . • • 62,500 New Zealand .. .. 55,000 Mexico • • • • 50,000 Irish Free State .. •. 30,000 Chile • • • • 30 > 000 ‘ ‘ CATHEDRAL” STUDIO. A “cathedral” studio has just been opened in Chicago by the National Broadcasting Company. It measures 75 ft by 45ft, and the domed ceiling is 40ft high in the centre. The studio was designed and built to accommodate the largest orchestras and to reproduce their music in its full tonal value. Ey skilful planning the acoustics have been made practically faultless; indeed any form of music can be broadcast successfully by the use of only two microphones, one in the dome and the other on a floor stand. Adjustable curtains around the walls and in the dome are used to control resonance. A large pipe organ is sot in one end wall. The Chicago Smyphony Orchestra broadcasts from the studio every Sunday evening. It is worthy of note that the 8.8. C. has provided for a very large studio in the new Broadcasting House to be erected in London. NEW TYPE MICROPHONE. A new type of condenser microphone is described by Professor Foley, of Indiana University, in a recent paper read before the National Academy of Sciences. It consists of two rigid metal plates separated by an air space. The. plates do not vibrate. They are initially charged with a biasing voltage so as to form a condensed with an air dielectric. The sound waves from the speaker's Voice are impressed upon the air between the plates so as to set up differences in the normal air pressure. As the dielectric value of air alters with its density, corresponding differences of voltage will appear across the condenser plates. These voltages are used to modulate the carrier wave in broadcasting. As there is no solid vibrating diaphragm, there can be no distortion due to inherent resonance effects. WAVE LENGTH ALLOCATION. . ! Short waves have been the salvation of the international radio authorities ■who allocate the wave length channels for world radio communication. The minimum separation of each radio channel, so as not to interfere with others, is 10 kilocycles. Take, for instance, the broadcast band of wave lengths which is approximately 200 to 500 metres. This represents a band of 900 kilocycles, no ninety 10-kilocycle channels in a wave length band of 300 metres. Now take the 10-metre to 200 metre channel, a band of 190 metres wide. We have a frequency band 28,500 kilocycles wide, which gives us 2850 separate channels. WAVE LENGTH AND FREQUENCY EXPLAINED. To those who are uncertain as to the relationship of wave length and frequency the following brief explanation may be of help: Radio waves travel at the same speed as light, approximately 300,000,000 metres per second, or 156,000 miles. If the wave length of a station is, say, 100 metres, each wave or cycle will travel 100 metres before the next one starts. In other words, the distance from crest to crest of the waves will be 100 metres, and in one second there will be 3,000,000 such waves or cycles. As such numbers are unwicldly we say 100 metres equals 3000 kilocycles; The lower the wave length, therefore, the higher the frequency as the distance between waive crests is less, and a greater number of waves, or cycles, occur each second.