. The Bell System technical journal . subjected to extreme variations in ambient temperature over shortperiods of operation some difiiculty in maintaining optimum focus wasexperienced. This defocussing, due to the change in coil resistance withambient temi)erature and in part to dissipation in the winding proper, isminimized in the designs shown by the introduction of a varistor element TEE RADAR RECEIVER 769 mounted in close proximity to the winding whose resistance temperaturecharacteristic was chosen to compensate for similar characteristics of thewinding proper. The beam centering structur
. The Bell System technical journal . subjected to extreme variations in ambient temperature over shortperiods of operation some difiiculty in maintaining optimum focus wasexperienced. This defocussing, due to the change in coil resistance withambient temi)erature and in part to dissipation in the winding proper, isminimized in the designs shown by the introduction of a varistor element TEE RADAR RECEIVER 769 mounted in close proximity to the winding whose resistance temperaturecharacteristic was chosen to compensate for similar characteristics of thewinding proper. The beam centering structure included in the designsshown employs two pairs of coils arranged upon a closed magnetic corestructure adjacent to the focus winding. The perpendicularly disposedmagnetic fields are produced by direct current in the same fashion as dis-cussed in connection with the deflection coil assembly. Figure 42 illustrates the operation of a permanent magnet type of focus-sing and centering structure developed during the war and which was em-. Fig. 41.—Constructional details—deflection coil design for AN/APQ-7 radar bombingequipment. ployed extensively in airborne radar applications. Here a permanent ringmagnet is equipped with a variable internal mechanical magnetic shuntwhereby the focussing magnet field can be varied as shown. The centeringof the beam is accomplished by means of a centering ring located as showncapable of being mechanically controlled along two perpendicular linkage arrangements provide location of the focus and center-ing adjustment controls on the indicator panel convenient to the permanent magnet type structure has the advantage of maintenance ofproper focus and centering under conditions of extreme variations in ambienttemperature. Similar permanent magnetic type structures have been em- 770 BELL SYSTEM TECHNICAL JOURNAL ployed to permanently deflect the beam for off-center displays such as theB-type and certain modified sector sc
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
