WIDE RANGE MICROWAVE SWEEPING OSCILLATOR 



557 



A crystal detector and an oscilloscope are used to view the output. It 

 is convenient to use a sinusoidal horizontal sweep on the oscilloscope, 

 driven from the same 6.3 volt transformer as the mechanical sweeping 

 mechanism. In this case, a phase shifter is needed to synchronize the 

 oscilloscope sweep with the motion of the tuning plunger, because there is 

 an appreciable mechanical phase shift in the loudspeaker mechanism. 



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ANODE 

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RADIAL 

 LINE 



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HJ CATHODE 



Fig. 3. — Simplified equivalent circuit of the oscillator. 



Fig. 4. — The complete oscillator, showing the output coupling window and the ridged 

 waveguide coupling transformer. 



When properly phased, the output spectrum will be displayed across the 

 oscilloscope screen with the minimum and maximum frequencies at oppo- 

 site ends of the trace. In addition, a vibrating relay (such as the Western 

 Electric 275 B Mercury Relay) is used to short out the input to the oscillo- 

 scope during half of each cycle. This converts the return trace into a 

 zero-signal reference line, so that the complete picture is a closed loop 

 with a flat bottom. The separation of the active from the reference trace 



