Radio broadcast .. (1922-30)

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1 12 RADIO BROADCAST Although told that it could not be done, this radio enthusiast operates a loud speaker downstairs from his upstairs receiving set, the two being connected by seventy-five feet of flexible cord columns have more to say regarding the erection of the antenna and the arrangement of the ground connection. The first consideration in the purchasing of a receiving set is to decide just what broadcasting stations are to be intercepted and how far away they are located from the proposed receiving station. The second consideration is how big an antenna can be erected. Naturally, since the antenna decides how much radio energy is intercepted, the smaller the antenna the less the radio energy intercepted, and therefore the better the receiving set must be to operate over a given distance. For receiving over distances of less than twenty-five miles, with a good antenna measuring 100 feet or more in length, elevated at least 20 feet above the ground or the roof of a house if it happens to be installed in a city apartment house, any one of the several inexpensive receiving sets, selling for about $15.00 to $25.00 will give satisfactory results. These sets generally consist of a simple tuning device, which permits of adjusting the set to any desired radio-phone station or radio telegraph transmitter within range, a simple crystal detector, and a pair of telephone receivers. The crystal detector is the device which converts the intercepted radio energy into audible sounds in the telephone receivers. It is the simplest kind of radio detector, requiring no ; battery of any kind for its operation. However, its sensitiveness is rather limited, so that for distances greater than twenty-five miles it is of little value. With inexpensive sets good results may be obtained from near by stations, but the impossible should not be expected. Thus it would be sheer nonsense to expect to operate a loud-speaking horn with a cheap outfit. Such loud-speaking devices, which make the radio receiving outfit somewhat akin to a phonograph in point of convenience and loud ! ness, can only be used with the most expensive types of receiving set. Furthermore, only one pair of telephone receivers should be used with an inexpensive outfit, because the amount of converted energy is very small, and an additional pair of telephone receivers cuts down the sound strength. Still, two pairs of receivers may be used if necessary. If louder music or speech is desired, even within a distance of twenty-five miles, it is necessary to turn to the more expensive offerings, in which the crystal detector is replaced by the vacuum tube. The vacuum tube detector resembles nothing so much as an Jectric lamp. It is provided with a filament, which glows like that of any electric lamp. However, it contains two other members, namely, a little helix or coil of wire which is known as the grid, and a cylindrical member known as the plate. The action of the vacuum tube is quite involved as far as the theory is concerned, but in practice it proves to be a far more sensitive device than the crystal detector. The crystal detector, as already mentioned, requires no battery. The vacuum tube, on the other hand, requires two batteries, namely, a filament battery, and a high-voltage plate battery or "B" battery, as it is called. The filament battery must be capable of supplying current to the filament for a long period of time. Most vacuum tubes require a potential of five to six volts and a current of one ampere for the filament, so that this heavy drain necessitates the use of a storage battery. For that reason many persons hesitate to employ a vacuum tube set because of the expense of purchasing a storage battery, and also because the storage battery must be watched and tested at intervals to determine when it