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. 



