MEASUREMENT OF PHASE DISTORTION 



547 



mission. In the upper part of the figure the resistance-frequency 

 curves are shown and the envelope delay-frequency curve derived 

 therefrom is shown in the lower part of the figure. The delay char- 

 acteristic for which this particular network was designed is also shown 

 for comparison and gives a rough idea of the accuracy of this method of 

 measurement. 



No figures are shown here which give the results of measurements 

 made by the methods referred to for determining envelope delay from 

 special phase shift measurements. Although the actual methods of 



2000 



3000 



4000 5000 



CYCLES PER SECOND 



6000 



7000 



8000 



9000 



Fig. 13 — Envelope delay characteristic of 737 miles of 16-ga. B-22-N program circuit. 



measurement in these cases are quite different from the impedance 

 measurement method, the delay results are obtained in a similar man- 

 ner, and these have just been illustrated by the figure above. 



Figs. 10, 11 and 12 show the results of direct measurements of the 

 envelope delay, using the method described above which has a modulat- 

 ing frequency of 25 cycles per second. Fig. 10 gives the measured 

 envelope delay-frequency characteristic for 231 miles of 19-gauge 

 H-174 side circuit. Fig. 11 gives the envelope delay-frequency char- 

 acteristics as measured for approximately 1560 miles of 19-gauge 

 H-44-25 side circuit and for approximately 1515 miles of 19-gauge 

 H-44-25 phantom circuit. Fig. 12 gives the corresponding characteris- 

 tic for 708 miles of 16-gauge B-22-N two-wire circuit. 



Fig. 13 gives the envelope delay-frequency characteristic for 737 

 miles of 16-gauge B-22-N cable circuit equipped with phase correctors 

 for program transmission.^"* The measurements for frequencies above 

 300 cycles per second were made with the measuring device using a 

 modulating frequency of 25 cycles while the measurements below 300 



'^ "Long Distance Cable Circuit for Program Transmission," A. B. Clark and C. W. 

 Green. To be presented at Summer Convention of A. I. E. E. at Toronto, June 1930. 



