TEE RADAR RECEIVER 



769 



mounted in close proximity to the winding whose resistance temperature 

 characteristic was chosen to compensate for similar characteristics of the 

 winding proper. The beam centering structure included in the designs 

 shown employs two pairs of coils arranged upon a closed magnetic core 

 structure adjacent to the focus winding. The perpendicularly disposed 

 magnetic 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 bombing 

 equipment. 



ployed extensively in airborne radar applications. Here a permanent ring 

 magnet is equipped with a variable internal mechanical magnetic shunt 

 whereby the focussing magnet field can be varied as shown. The centering 

 of the beam is accomplished by means of a centering ring located as shown 

 capable of being mechanically controlled along two perpendicular paths. 

 Mechanical linkage arrangements provide location of the focus and center- 

 ing adjustment controls on the indicator panel convenient to the operator. 

 The permanent magnet type structure has the advantage of maintenance of 

 proper focus and centering under conditions of extreme variations in ambient 

 temperature. Similar permanent magnetic type structures have been em- 



