EXPONENTIAL TRANSMISSION LINE 



567 



was decided to introduce each of these factors one at a time. This test 

 was made on a 600 : 300 ohm Hne constructed of No. 6 copper wire with 

 lockstitch insulators except at the terminals. The correct termination 

 was obtained by tests on a uniform 300 ohm line with the same physical 

 structure at the termination. Of necessity the tying of the wire to the 

 strain insulators at the end introduced a shunt capacitance which 

 augmented the inherent additional capacitance due the "end effect." 

 This additional capacitance is equal to that of a short length of line. 



Fig. 5 — Photographs of terminations of 300 ohm line, 

 upper right for curve 1 1 

 lower for curve 2 ^ of Fig. 6. 



upper left for curve 3 J 



If the correct amount of inductance is inserted in series with the 

 resistance load the combined effect of the additional capacitance and 

 inductance becomes the same as the addition of a small length of line 

 for all frequencies up to those for which this length of line is an appre- 

 ciable fraction of a wave-length. Accordingly a small amount of induc- 

 tance was inserted in series with the resistance as shown in the right 

 picture of Fig. 5. The input impedance of the uniform line with this 

 termination is given by "Experimental Curve 1 " at the bottom of Fig. 6. 



