. Radio for everybody; being a popular guide to practical radio-phone reception and transmission and to the dot-and-dash reception and transmission of the radio telegraph, for the layman who wants to apply radio for his pleasure and profit without going into the special theories and the intricacies of the art . including a ILttle back history. Loud-speakers ofthis kind are known as electrodynamic receivers. The Early Days of the Electrodynamic Receiver In 1911 two inventors, E. S. Pridham and P. L. Jen-sen, were actively affiliated with the development of arcradio transmission and reception at
. Radio for everybody; being a popular guide to practical radio-phone reception and transmission and to the dot-and-dash reception and transmission of the radio telegraph, for the layman who wants to apply radio for his pleasure and profit without going into the special theories and the intricacies of the art . including a ILttle back history. Loud-speakers ofthis kind are known as electrodynamic receivers. The Early Days of the Electrodynamic Receiver In 1911 two inventors, E. S. Pridham and P. L. Jen-sen, were actively affiliated with the development of arcradio transmission and reception at Napa, the course of work, they made a very exhaustivestudy of various methods for the reception of rapid radiosignals. Naturally enough, the development of what isknown as the string galvanometer was carried out, andit was while conducting these experiments that severalnew and improved receiving devices were built. Amongthem was the first step in the development of the electro- RADIO FOR EVERYBODY 195 dynamic receiver, now well known for its loud-speakingcharacteristics. This early type was built along the lines of a modernvoltmeter, with a revolving coil in a magnetic field at-tached by lever action to a diaphragm. This, however,was not a success as a telephone receiver, and while it. Special power amplifier, used in connection •with extra power-ful loud-speakers such as are employed for projecting the radio-phone entertainment in a large hall. This amplifier is used inaddition to the usual amplifier of the receiving set. did reproduce the voice with remarkable distinctness, itwas not nearly loud enough, or even as loud as the or-dinary electromagnetic type. While this instrument wasnot important in itself it was to be taken into considera-tion as the forerunner of the practical electrodynamicreproducer of today. 196 RADIO FOR EVERYBODY After many experiments with the revolving coil, theidea was definitely given up and a new line of experimentsstarted. The
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