THE RADAR RECEIVER 755 



is arranged to be normally nonconductive except during the application of 

 a clamping pulse bias introduced as shown. During this clamping interval, 

 the grid circuit point of the condenser is re-established to reference poten- 

 tial by the low impedance of the conducting diode circuit. At the time of 

 decay of the clamping pulse wave forms the operation of this circuit follows 

 the principles of the d-c restorer types just described. This circuit has 

 been employed less extensively than the preceding simple d-c restorer 

 methods because of the relatively more complex arrangement, but has an 

 advantage in that the impressed signal may be clamped to a convenient 

 reference potential at any particular repetitive point in the cycle. 



2.34 Typical Radar Receiver Video Amplifier Circuits 



The radar receiver video amplifier signal output is required to modulate 

 the indicator by either position or intensity change. In the A type of 

 display the video signal is usually impressed upon a pair of vertical de- 

 flection plates of an electrostatic type of cathode-ray tube to present the 

 amplitude characteristics of the signal while the range to the target is 

 displayed as the horizontal coordinate. The maximum video signal am- 

 plitude required here to deflect the beam satisfactorily is usually of the order 

 of several hundreds of volts. In the case of B, C, and PPI forms of display 

 the radar video signal is required to intensity modulate the cathode-ray 

 tube. Here a maximum video signal amplitude of 50 volts is commonly re- 

 quired by the radar indicator. 



In certain military radar system applications it is desirable to locate the 

 indicator component at some distance from the main radar receiver and 

 video amplifier assembUes. This requirement is commonly encountered 

 in large naval vessel installations where the main radar components may be 

 located below deck and the indicator mounted as a part of the gun pointing 

 mechanism. In such cases video amplifier designs employing video trans- 

 former coupling between the output amplifier stage and a coaxial trans- 

 mission line and between the line and the indicator circuit proper, have 

 proven to be entirely successful. 



The development of video pulse transformers for radar purposes repre- 

 sents a considerable advance in the art of communication transformer de- 

 sign. The greatly improved wide frequency band performance of these 

 components is the result of the employment of improved magnetic core 

 materials such as supermalloy having relative permeabilities upward of four 

 times that available in the permalloy materials, improved techniques of 

 coil winding distribution, and the use of additional network elements in the 

 final configuration. Figure 35 illustrates the constructional features of 

 such a video pulse output transformer which has a band width extending 



