. Practical wireless telegraphy; a complete text book for students of radio communication . type of key is employed. One type manufactured by the Mar-Fig. 137-A Hand Manipulated Telegraph Key. coni_ Company appears in Fig. 137., , . ^, ... Earlier types had platinum points forbreakmg the current, but silver contacts of increased area have proven a satis-factory substitute. The circuit of an electromagnetickey is shown in Fig. 138. A pair ofmagnets M, Mi are wound to approxi-mately ISO ohms resistance and con-nected to 110 volts D. C. through asmall W. U. sending key. Extra , B a
. Practical wireless telegraphy; a complete text book for students of radio communication . type of key is employed. One type manufactured by the Mar-Fig. 137-A Hand Manipulated Telegraph Key. coni_ Company appears in Fig. 137., , . ^, ... Earlier types had platinum points forbreakmg the current, but silver contacts of increased area have proven a satis-factory substitute. The circuit of an electromagnetickey is shown in Fig. 138. A pair ofmagnets M, Mi are wound to approxi-mately ISO ohms resistance and con-nected to 110 volts D. C. through asmall W. U. sending key. Extra , B are mounted on the arma-ture and stationary posts which maybreak 50 or 60 amperes without type has a solenoid windingwith a plunger extending into a box ofoil. The contacts make and break thecircuit under oil, reducing arcing to aminimum. In certain high power stations spe-cially constructed electromagnetic keysinterrupt the circuit from the secondary ^^- 138—Circuits of Magnetic Key. winding of the transformer instead of the primary. 500 kilowatls can be broken in this. 110 VOLT PART VIII. AERIALS OR ANTENNAE 112. Function of the Aerial. 113. Determination of theWave Length From the Dimensions of an Fundamental Considerations. 115. Various Types ofAerials. 116. Directional Aerials. 117. Standard Mar-coni Aerial. 118. The Deck Insulator. 119. Installa-tion OF the Aerial. 120. Earth Connection. 121. Radia-tion. 122. Antenna Decrement. 123. TransmissionRange. 112. Function of the Aerial.—The function of the aerial or antennae of anygiven radio station is two-fold: (1) To radiate energy in the form of electromagnetic waves; (2) To absorb part of the energy radiated by the distant transmitter. The stations employing two aerials, one for transmitting and one for re-ceiving are few in number; in fact, the great majority of wireless stations employa single antenna for both purposes, which in its simplest form consists of a wireof silicon bronze, copp
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
