MICROWAVE REPEATER RESEARCH 



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testing method permits a study of the shapes of rectangular pulses which 

 have passed through a repeater amplifier many times, and thus simulates 

 transmission through a relay system with many repeaters. Figure V-20 

 shows an example of the results obtained from such tests made on the IF 

 amplifier alone. The top row shows a 1.25-microsecond test pulse after 1, 



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 FREQUENCY IN MEGACYCLES PER SECOND 



Fig. V-18. — Delay characteristic of RF amplifier. 



10, and 30 trips through the IF amplifier. Part of the distortion appearing 

 after one trip through the amplifier was in the viewing oscilloscope. It 

 was difficult to detect distortion from a single trip through the amplifier, 

 but Fig. V-20 demonstrates how it increases with successive trips. The 

 second row of pulse pictures shows the improvement achieved by adding 

 phase equalizers to the circuit. It was particularly noticeable in this test 

 that without equalizers the details in the shape of the pulse after 10 or 30 

 trips were very sensitive to the exact value of the intermediate frequency. 



