THE L3 SYSTEM EQUALIZATION AND REGULATION 



849 



network would insert a deviation characteristic 



e =/(i2r)-/(co)db. (12) 



Such a network would yield a given shape independant of setting and 

 thus would have linearity as well as symmetry. Actually the Bode net- 

 work has symmetry but only approximates linearity. As shown, it may 

 be designed to insert a variable impedance either in series or in shunt 

 with the line. When using only one control element it is not a constant 

 resistance structure and must be operated between terminations of the 

 design value. The choice of series or shunt configuration was governed 

 for L3 by the fact that very low thermistor resistance would require ex- 

 cessive dc currents from the regulators. For a 75-ohm circuit and this ther- 

 mistor hmitation the series regulator provides lower normal-setting loss. 

 The insertion gain for the series regulator may be written as: 



d 



<?. + 2arctanh[|^.pe-^^], 



where ^.v = The normal setting fiat loss as given by 



■p 



aif = 20 log ~ decibels. 

 ti 



r^VCV-i 



CONSTANT 



R 



NETWORK 



-vw 



SYMMETRY 

 RESISTOR 



(13) 



(14) 



GENERATOR 



LOAD 



(a) SERIES TYPE 



GENERATOR 



SYMMETRY 

 RESISTOR 



CONSTANT 



R 

 NETWORK 



Rt 



LOAD 



(b) SHUNT TYPE 



Fig. 5 — Block diagram of Bode Regulating Network, 



