428 



BELL SYSTEM TECHNICAL JOURNAL 



in less than one-fourth per cent frequency range on either side of the 

 pass band. 



Figure 21 shows the insertion loss characteristics of a filter employed 



55 

 50 



|45 



140 



I 



;35 



,30 



I 25 



; 20 



; 15 



Fij 



144 146 148 150 152 154 156 158 160 162 



FREQUENCY IN KILOCYCLES PER SECOND 



;. 21 — Measured insertion loss characteristic of a band-pass filter used in a single 

 side band radio receiver. 



in an experimental radio system for separating the two sidebands of a 

 channel at a high frequency. Here the separation- is effected in about 

 0.15 per cent frequency range. With the best electrical filters the 

 frequency space required for such a separation is about 1.5 per cent. 

 Figure 22 shows the insertion loss characteristic of a high-pass filter 



100 



210 



:30 250 270 290 310 330 350 370 



FREQUENCY IN KILOCYCLES PER SECOND 



Fig. 22 — Measured insertion loss characteristic of a high-pass filter. 



