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RADIO BROADCAST
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number (or a wide band) of wave frequencies and so produce interference in receivers sharply tuned to single (or narrow bands of) frequencies.
3. Most radio receivers will select sharply between waves having frequencies a few thousand cycles apart if the intensities of the two
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waves are equal, but will not exclude interference from a very intense signal wave even though its frequency be widely different from that of the weak desired signal.
Because of these difficulties, the number of independent, or non-interfering channels is still quite highly restricted. In fact, it is safe to say that a closely adjacent wireless transmitter of the spark type can effectively prevent reception (despite the use of the best receivers on the market) from a distant transmitter, even though the interfering spark wave has a basic frequency hundreds of thousands of cycles different from that of the desired signal wave.
The greatest single advance which can now be made toward an interference-free multiple
independent-channel condition for radio operations is the restriction of transmitting stations to the modern types which radiate almost their entire power at practically a single basic transmitting wave frequency. This change, which would involve elimination of many spark transmitters from the radio scheme of things (or, at
least, their segregation upon wave frequencies widely different from those used by high-grade selective sending stations) would give opportunity for the effective use of sharply tuned interference-excluding receivers. The number of stations which could work independently in a given territory would be greatly increased, for the greatest source of radio interference would be done away with. There is a strong probability that this step forward will soon be taken; legislative inquiries are now under way to determine how new laws may be framed to aid in reducing interference, and this particular remedy is receiving such full consideration that it is likely to be among the first which will be adopted.
FREQUENCY IN THOUSANDS OF CYCLES PER SECOND
A chart showing, in the same way, the state of aflfairs which would exist if the interfering broad-wave station were twice as powerful as each of the three others. In this instance the interference would be so powerful over the 725,000 to 825,000 cycle range that the 360 meter station (833,000 cycles) could hardly be heard at all. Even the 400 meter station (750,000 cycles) would be difficult if not impossible to understand. Only at the margins of the interfering wave, as with the 870,000 cycle station (345 meters) would reception be possible at all through the interference
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