DISTORTION CORRECTION 



SOI 



A comparison of the propagation characteristic of a line section and 

 that of its simulating network is shown in Fig. 24 for three different 

 line lengths, / = 10, 20, and 30 miles. Even in the longest section 

 the simulation is good up to 3000 cycles per second. The iterative 

 impedances are, of course, identical as in Fig. 25. 



1800 

 1600 



moo 

 noo 

 woo 



^ 600 



I 



^ 400 



I 



200 







-ZOO 



-too 



-600 



WOO woo 3000 4000 5000 



Frequency (cycles per second) 



Fig. 25 — Iterative impedance of 104-mil open-wire smooth line and of the simulating 



artificial smooth lines. 



While the above general design considered four parameters, a 

 similar procedure can be followed with other networks having a smaller 

 or greater number of parameters. The structure can be obtained 

 by building the series impedance of any section out of various com- 

 binations of the impedance elements Za and 25. However, several of 

 the above four-parameter composite sections can perhaps meet most 

 design requirements. 



Appendix 1 

 Discussion of Linear Phase Intercept 



Let us first consider steady-state transmission over a circuit where 

 the impressed e.m.f., consisting of simple sinusoids of any two angular 

 frequencies co] and C02, is given by 



E{t) = sin coit + sin co2^ 



= 2 cos |(co] — wo)^ sin |(coi + coo)!- 



(89) 



Assume that the circuit has at these frequencies the transfer exponents 

 fli + ibi and 02 + i&2 such that ai = a2 = a'. A straight line drawn 



