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A. B. CHAMBERLAIN,
Chief Engineer
Columbia Broadcasting
System, Inc.
THAT the power output from one microphone is so small that it would require the combined output of twenty-four billion microphones — or about twelve to every human being on earth — to produce sufficient power to light an ordinary 40-watt electric light bulb. Broadcast microphones produce only .00000000166 watts. This is amplified thirty trillion times (30,000,000,000,000) before being broadcast from a 50,000-watt station. This is accomplished without distorting the character of the original complex sound wave.
SOUND WAVES
That radio waves travel with the same velocity as light — 186,000 miles per second. This is equal to a distance seven and one-half times around the world? Audio signals transmitted over telephone circuits, such as are used for network transmission, have a velocity of approximately 20,000 miles per second. Contrast this with the speed of sound waves, which is approximately 1100 feet per second. Because of the difference between the speeds of radio and sound waves, a broadcast listener in California, or a short-wave listener on the opposite side of the world, can hear a program broadcast from the stage of a New York CBS Playhouse before a spectator seated in the last row of the orchestra hears it.
OPERATING FREQUENCY
That radio engineering is one of the most exact of sciences? The operating frequency of most American broadcast stations is maintained with 10 cycles of its assigned frequency. At 1000 kilocycles, this represents a deviation of only ten parts in one million.
RECEPTION
That geography has a lot to do with radio reception in your home? The primary service area of a broadcast station is dependent upon the station location, frequency, power, soil conductivity, topography, antenna radiating efficiency, interference from other
stations and interference created by electrical noises — both man made and natural.
1937 BROADCAST HOURS
That more than 3,250,000 hours of broadcasting took place in the United States this past year? Nine stations operated by CBS originated 100,000 programs during this period. Of these 100,000 programs 20,000 originated for the Columbia network from the New York studios alone. This vast amount of entertainment was made available to 25,000,000 radio homes and 4,000,000 radio equipped automobiles. There are at the present more than 100,000.000 radio listeners in this country.
FADING
That fading is caused by the "sky" and "ground" wave signals, radiated from a single location, arriving at the point of reception over paths of different distance? This results in the signal being received at different intervals of time. Broadcast receivers that use automatic volume controls compensate to a great degree for "carrier" frequency fading but are not capable of eliminating "selective" fading, which is the result of the "carrier wave" and side band or audio frequencies fading at different time intervals. This phenomena identifies itself by "mushy, distorted" reproduction. Fading is a transmission evil which engineers are continually investigating in the hope of eventual reduction or pos
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