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BELL SYSTEM TECHNICAL JOURNAL 



In calibrating microwave attenuators and pads, comparison with an 

 accurately calibrated IF attenuator, using a heterodyne test set, has been 

 found to give excellent results. 



RF Cables and Connectors 



Flexible RF cables for connecting test equipment to equipment under 

 test are an important adjunct of field testing. At frequencies of 10,000 mc 

 and below, flexible coaxial cables of about .4" over-all diameter with solid 

 or stranded inner conductor, solid low-loss dielectric (polyethylene) and 

 braided outer conductor have been used satisfactorily, although in the upper 

 part of this range special measures have been necessary to prevent attenua- 

 tion change due to flexure and aging. Over most of this range coaxial jack 

 and plug connections have been found satisfactory but wave guide connectors 

 are preferable at the upper end. In the range above 10,000 mc, coaxial 



T 

 % 



1. 



^ 







■^RF 



© 



OSCILLOSCOPE 



NORMAL PULSE 



DOUBLE MODING 



PULSE SKIPPING 

 OR MISFIRING 



FREQUENCY JUMPING 

 DURING PULSE 



Fig. 24 — Radar pulse envelopes. 



cables of requisite stability have not yet been obtained and rubber covered 

 wave guide with soldered articulated joints is the best form of flexible cable 

 now available. 



Oscilloscopes 



Oscilloscopes are used extensively in radar maintenance (a) for examina- 

 tion of video waves and (b) for viewing RF envelopes. Satisfactory radar 

 performance depends on a variety of video wave shapes which may include 

 trapezoidal or triangular pulses, sawtooth waves, square waves or com- 

 binations of these. Observation of these wave shapes, supplemented if 

 necessary by measurements of amplitude and duration, helps in diagnosing 

 many troubles. 



Examination of the envelope of the RF pulse is a convenient but less 

 informative alternative to spectrum analysis. The envelope should be a 

 clean, single trace of good shape. Figure 24 shows traces sometimes experi- 



