. Practical wireless telegraphy; a complete text book for students of radio communication . ning coil, as a simple open circuit oscillator, may bemeasured by the circuit and apparatus shown in Fig. 226. The radio-frequency coil A, B, is set into excitation by an aperiodic buzzer circuit whichincludes the 1 mfd. condenser C-1 and the resistance R of 2,000 ohms. The wavemeter, fittedwith a sensitive detectorD, is placed in inductiverelation to the coil in theusual manner. If thecoil possesses a fairvalue of distributed ca-pacity, the resonant pointon the wavemeter willbe sharply defined, but,lac
. Practical wireless telegraphy; a complete text book for students of radio communication . ning coil, as a simple open circuit oscillator, may bemeasured by the circuit and apparatus shown in Fig. 226. The radio-frequency coil A, B, is set into excitation by an aperiodic buzzer circuit whichincludes the 1 mfd. condenser C-1 and the resistance R of 2,000 ohms. The wavemeter, fittedwith a sensitive detectorD, is placed in inductiverelation to the coil in theusual manner. If thecoil possesses a fairvalue of distributed ca-pacity, the resonant pointon the wavemeter willbe sharply defined, but,lacking this, the point ofresonance may be some-what difficult to locate. 175. Measurementof Electrostatic Ca-pacity.—(a) Capac-ity at low voltage andaudio-frequencies. Wemay measure the sim-ple electrostatic ca-pacity of a condenseror an aerial by thebridge method of The condenserof unknown capacityis shown at C-x, anda standard variablecondenser calibratedin microfarads at and R-2 are non-inductive resistancesof low value such asfound in the usualsliding wire bridge, P. Wjm^ ill Fig. 227—Diagram for the Measurement of Electrostatic Capacity. 208 PRACTICAL WIRELESS TELEGRAPHY. and S are the primary and secondary windings respectively of an ordinary tele-phone induction coil. A buzzer and battery are connected in series with P. Thisapparatus afifords a source of electromotive force for obtaining balance of thebridge. To carry out the measurement, the buzzer is set into vibration and the values of R-1 andR-2 varied until complete silence or a minimum of sound is heard in the telephone P-1. Thevarious quantities are then related as folows: C-x R-2 R-2 = or C-x = X C-n C-n R-1 R-1 If condensers C-x and C-n have different dielectrics, complete silence cannot be obtained,hence a minimum of sound is an indication of balance. To carry out the measurement forlow values of capacity, the total resistance of the sliding wire bridge, need not exceed 110 ohms. If the aeria
Size: 1740px × 1436px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
