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BELL SYSTEM TECHNICAL JOURNAL 



100 db which is usually provided in a main IF amplifier that can be located 

 conveniently within the receiver indicator portion of the radar system. The 

 main IF amplifier is commonly designed as a complete shielded unit, required 

 by the high-gain concentration and desirable from the standpoint of allowing 

 the same unit to be used in several radar systems. Three IF amplifiers are 

 shown in Fig. 30 which well illustrates the technological development in this 

 field during World War II. The first amplifier employing 6AC7 tubes was 

 developed at the beginning of the war, has an over-all gain of 95 db with an 

 appro.ximate band width of 2 mc, and employs synchronous single-tuned 



Fig. 30. — T\-pical IF amplifier c(|ui[Miient designs for military radar ap])lications. 



interstage networks. This design was employed extensively in early mili- 

 tary radar equipments for land, sea, and air use. It has a total power con- 

 sumption of 31 watts and weighs 2 pounds 4 ounces. The second amplifier 

 illustrated was de\-el()ped early in the war primarily for airborne search and 

 interception radar systems and employs 71 7A pentodes with a double-tuned 

 and single-tuned interstage combination of networks to produce a gain of 

 85 (11) with an over-all band width of 4 mc. The total power consumption is 

 11 watts and the weight here has been reduced to 1 jiound 14 ounces. This 

 design of li' aniplilier with minor modil'ications was employed on the major- 



