318 BELL SYSTEM TECHNICAL JOURNAL 



In an effort to get high power from the 725A magnetron operating on long 

 pulses, considerable work was done to build a cathode for a power input of 

 225 kw. While a few thousand such magnetrons were made and tested at the 

 higher test condition, entirely satisfactory operation was never achieved. 

 Magnetrons tested at 225 kw. input were coded the 2J53/725A but after 

 the first production run were not manufactured again. The 4J50 and 4J52 

 magnetrons are now available for this range of operating conditions. 



Fig. 69 — The 2J55 magnetron (55 kw., 9375 mc/s) — the "packaged" version of the 

 725A. Compare with the size of the 725A and its magnet shown in Fig. 44. 



17.3 The 2 J 55 and 2 J 56 Magnetrons: The 2J55 and 2J56 are by- 

 products of the development of a tunable 3 cm. magnetron, the 2J51, de- 

 scribed below. The 2J51 design, being "packaged" and thus lighter and 

 more compact than the 725A and its magnet, with which it is interchange- 

 able, was ideally suited for conversion into a fixed frequency, "packaged", 

 3 cm. magnetron. The only design changes required were those associated 

 with the removal of the tuning mechanism and the change in dimensions of 

 the resonator system needed to bring the wavelength to the proper value. 

 The two magnetrons designed in this way for operation at the wavelengths 

 3.2 and 3.25 cm. were coded the 2J55 and 2J56, respectively. Each weighs 

 3 lbs. 12 oz. as compared to the weight of 11 lbs. 2 oz. of the 725A mag- 

 netron and its magnet. 



