TYPE-O CARRIER SYSTEM 



709 



-30 -20 -10 



INPUT IN DECIBELS 



Fig. 18 — Typical group receiving and repeater regulator characteristic. 



it controls in any case. There are other important differences, however, 

 between X and channel regulators. In N the channel regulator follows 

 the channel band filter and thus tends to compensate for its flat trans- 

 mission variations. Also the N regulator is controlled from the demodu- 

 lator dc output and thus compensates in some degree for demodulator 

 variations. In O, the twin-channel control is ahead of both the chaimel 

 band filter and the channel demodulator, and therefore does not make 

 up their variations. 



A statement might be intei-polated at this point to emphasize that 

 the relative advantages of single-sideband and double-sideband trans- 

 mission are by no means easily listed and evaluated, since the differences 

 are many and devious, some necessarily and some fortuitously. An ex- 

 ample worthy of note is that in N it is necessary to be concerned about 

 relati\'e phase shift of the sidebands and in the instances of longer cir- 



-9 -8 -7 -6 -5 -4 -3 -2 -1 



CHANGE IN CARRIER INPUT IN DECIBELS 



Fig. 19— Typical twin-channel regulator characteristic. 



