THE L3 SYSTEM — EQUALIZATION AND REGULATION 



867 



2 5 0.1 



FREQUENCY 



2 e. ,0 2 5 



IN CYCLES PER SECOND 



Fig. 19 — Loop gain characteristic for the line regulator. 



through resonances due to the crystals and introduces a gain character- 

 istic on the hne that cannot, in practice, be equahzed. Thus it is neces- 

 sary to hide the filter from the line with loss. To hold the transmission 

 distortion of signals to 0.15 db with 500 regulators (0.0003 db per regu- 

 lator) requires a voltage loss of 23 db with the filter impedance changing 

 by large factors from its nominal 25,000-ohm level. The power loss 

 bridging on the 37.5-ohm (75 into 75) circuit is, of course, much greater. 

 The 7,266-kc pilot level at the line amplifier output is —16 dbm into 

 75 ohms. The filter and pad loss totals 24 db (voltage ratio) leaving an 



.-7^ 6 



lU 4 

 a 



z 



I 



5 6 



20 30 40 60 80 100 200 



FREQUENCY IN CYCLES PER SECOND 



400 600 



Fig. 20 — Feedback characteristic for the line regulator showing the gain en- 

 hancement effect. 



