MEASUREMENT OF DELAY DISTORTION 



i61 



variations cause changes in the relative phase of the two successive meas- 

 urements required when using the circuit of Fig. 5 which do not represent 

 changes in the delay. In effect the circuit of Fig. 8 makes the two phase 

 measurements simultaneously, and thus eliminates effects due to variations 

 of phase with time. 



X 10' 



45 



40 

 10 

 Q 



Z 

 O 35 



Q 25 



<20 



15 



10 



52 



58 60 62 64 66 68 70 72 



FREQUENCY IN MEGACYCLES PER SECOND 



78 



Fig. 12 — Measured curve of the relative delay of an intermediate frequency amplifier 



Results 

 Figure 11 shows a photograph of the delay measuring equipment which 

 has been described. With the aid of patch cords and switches that have 

 been included in the equipment this apparatus can be set up according to 

 either Fig. 5 or Fig. 8. The ganged oscillators are on the panel above the 

 oscilloscope box. The box contains the dividing attenuators, detectors, 

 amplifiers and oscilloscope. A separate power supply is required for the 

 oscillators and the output stages of the amplifiers. A number of different 

 lengths of flexible coaxial cable are mounted on the panel above the oscil- 

 lators and arranged so that various lengths of balancing line can be con- 

 veniently obtained by patching. The coaxial phase changer can be seen 

 on the shelf in front of the oscilloscope. 



