. An elementary manual of radiotelegraphy and radiotelephony for students and operators . et must be very narrow and closetogether, not more than two or three millimetres in width, to securethe necessary fretiuency with available si)eeds of rotation, it isessential to place all the teeth of one polarity on the same side toavoid magnetic leakage. This then results in the selection of tlie 334 RADIOTELEGRA PHY Mordey type of alternator with fixed non-iron armature andrevolving fields. It is not necessary to generate very high , as we canalways transform it up J3y an oscillation transformer
. An elementary manual of radiotelegraphy and radiotelephony for students and operators . et must be very narrow and closetogether, not more than two or three millimetres in width, to securethe necessary fretiuency with available si)eeds of rotation, it isessential to place all the teeth of one polarity on the same side toavoid magnetic leakage. This then results in the selection of tlie 334 RADIOTELEGRA PHY Mordey type of alternator with fixed non-iron armature andrevolving fields. It is not necessary to generate very high , as we canalways transform it up J3y an oscillation transformer or byresonance, but it is necessary to have high frequency. K. A. Fessenden (see The Electrician, Vol. 61, p. 441, 1908)has constructed a high frequency alternator direct coupled to aDe Laval turbine, giving a current at 225 volts, with a frequencyof 75,000 and about 2*5 kw. output. The machine is of thedouble armature type, with 300 coils on each, and a field with150 teeth. The two air-gaps are only -^^ inch in length (seeFig. 3). The required steam pressure is 100 lbs. on sq. {Reproduced hy permission from The 3.—High Frequency Turbo-Alternator (Fessenden). Also Alexanderson has constructed high frequency inductoralternators as described in Chapter III. A disadvantage of such machines is that they are non-portableand not suitable for use on board ship. Nevertheless, in landstations it would appear to provide a possible form of generatorfor long-distance radiotelephony. 3. Electric Arc Transmitters for Radiotelephony.—Turningthen to the other method already described for the production ofundamped oscillations by means of the electric arc in a hydro-carbon atmosphere, we find that V. Poulsen has brought such arcoscillation generators to a considerable degree of perfection, and RADIOTELEPHONY 335 api»liiil tlioui alsct very siuicssliilly in the iraiismiHsiun of speechfor very CDUsiderahK! tiistaiices over hind ami sea. Ah the uiethixl of proiimiii,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1916
