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into the magnetron lead. In the partial section shown at (b), this outer 

 cylinder is not used and the joint occurs at the end of the section where there 

 is a current antinode. In this method there exists the greater possibility 

 of sparking should the coupling not be clamped tightly. A folded quarter 

 wavelength section is built into the inner conductor. If the wavelength is 

 short enough, as in the 5J26 and the 720 A-E (see Figs. 58 and 63), this 

 section need not be folded, the inner post on the magnetron center conductor 

 can be eliminated and replaced by a solid center conductor on the load side. 



Fig. 47 — A schematic diagram of the type of coaxial output circuit used in a number of 

 magnetrons of wavelength 10 cm. or greater. Of particular interest are the means of con- 

 tact-free or "choke" coupling employed in the inner and outer conductors, consisting of a 

 folded concentric line section which presents zero impedance at the gap in the conductor, 

 (a) and (b) represent two variations'of the "choke" in the outer conductor as explained in 

 the text. 



The more recent designs of magnetrons for wavelengths greater than 10 cm. 

 have some form of this coupling. 



The impedance required at the output coupling to load the 728A-J mag- 

 netrons for sufficient power output necessitated a rather high standing wave 

 in the output line. This standing wave was provided by a transformer built 

 into the radar system to which the magnetron was attached. This caused 

 no trouble since the output power was below the point where RF voltage 

 breakdown in air in the line or coupling would occur. The press of time 

 necessitated the adoption of this output circuit although "preplumbing" by 

 incorporation inside the vacuum of the necessary transformer action for 

 coupling directly to a matched load line would have been preferable. Such 

 a design was executed but its completion came too late for its incorporation 

 into the manufacturing specifications. 



