THE L3 SYSTEM — EQUALIZATION AND REGULATION 



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FREQUENCY IN MEGACYCLES PER SECOND 



Fig. 25 — Regulator selectivity without the crystal filter. 



cathode current. In so far as trans-conductance depends upon cathode 

 current, trans-conductance changes are reduced. This is of material 

 value in further reducing the effects of vacuum tube aging. 



Fig. 25 shows the external gain of the 7,266-kc amplifier without 

 the crystal filter. The filter response is shown in Fig. 26. The relatively 

 wide 3 db bandwidth of ±1.5 kc is to reduce the contribution of the 

 filter to the gain enhancement problem. The large rejections to fre- 

 quencies further removed from the pilot prevents operation of the regu- 

 lator by signals other than the pilot. Also note that for very strong signals 

 such as the television carrier at 4,139 kc the filter is aided by the am- 

 plifier selectivity. 



The diode detector is also designed to reduce the effects of inter- 

 ference. The time constant of the detector is made short so that the 

 output will follow envelope fluctuations up to about 40 kc. Thus the 

 output of the detector in the presence of an interfering signal within 

 40 kc of the pilot becomes the power sum rather than the voltage sum of 

 the two signals. This is readily understood from Fig. 27. Here Ej, is 



