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BELL SYSTEM TECHNICAL JOURNAL 



pick-up wire extending through the walls of the hollow cylinder. This 

 form of wave-meter is moderately fast and permits w^ave-length differ- 

 ences of one or two hundredths of a centimeter to be readily detected. 



Miscellaneous Apparatus 



Sometimes it is desirable to change the length of a pipe without 

 changing its diameter. For this purpose telescoping pipe is to be 

 avoided. A pipe with removable sections may, however, be provided. 

 Units of 10 cm., 5 cm., 2 cm., 2 cm. and 1 cm. have been found con- 

 venient. They are aligned in a slightly larger half-section of the same 

 kind of pipe which provides their support. 



It may be desirable at times to investigate the field inside a pipe to 

 determine if standing waves are present. This may be done by mount- 

 ing a detector similar to that shown in Fig. 15, on a carriage so it 

 may be advanced along a slot cut in a piece of wave guide perhaps 

 60 cm. long. Often it is necessary to pass from one size of pipe to 

 another. A conical reducer perhaps 30 cm. long may be used for this 

 purpose. 



It is usually desirable to construct components such as the above 

 with lengths of some integral number of centimeters such as 10 cm., 

 20 cm. or 50 cm. This obviously facilitates the addition of the 

 component lengths used and often simplifies calculation. 



It is obvious from the above that a laboratory working with wave 

 guides must use for its circuit components such unusual electrical 

 items as hollow* pipes, movable pistons and iris diaphragms. These 

 should be capable of quick assembly into a variety of forms, sometimes 

 as a generator, sometimes as a tuned receiver and sometimes as a 

 termination. This object imposes a wide range of requirements that 

 can best be met by mounting the parts by means of clamp supports 

 on a saw-horse arrangement or wave guide bench such as shown in 

 Fig. 17. 



TERMINATION 



Fig. 17 — Bench mountings with typical apparatus used at the transmitting and 

 receiving ends of an experimental wave guide. 



