Reference: NAVSHIPS 91875(A), para 2h(5)
(See figure 2-3). Signals at 200 kc from the plate of V1003 are also applied across the diode detector V1005, through the broadly tuned transformer circuit Z1011. An audio voltage is developed across the diode load, R1027, and applied to the audio amplifier noise peak limiter V1101 through S1003, J1002K, J1101T, and R1102 when the RECEPTION control is in the A2 or A3 position.&
The voltage developed by the diode detector V1005 across R1027 is applied, through R1028 and link O1003 to the AGC delay diode, V1006, when the RECEPTION control in in the FSK or A3 position (AN/SRR-12 and -13 only). Capacitor C1053 in conjunction with R1028 serves to filter the modulation components of the detected signal so that only the d-c component is applied to the AGC diode. This diode is normally conducting by reason of a positive voltage applied to its plate from the B+ regulated supply through R1029. Therefore the AGC line to the r-f and second i-f amplifiers is held at a slightly positive potential until the d-c component of the signal developed across the diode load R1027, is sufficiently negative to stop V1006 from conducting. The voltage divider network R1027, R1028, and R1029 is so arranged so that the point where the diode (V1006) stops conducting corresponds to approximately 12 volts d-c at the detector (V1005). For stronger signals the AGC line becomes negative by an amount necessary to bias the r-f and second i-f amplifiers and reduce the gain in these stages.
Delayed AGC is effective only for F1 and A3 reception in the AN/SRR-12 and -13. It is not used on the AN/SRR-11 receiver, in which case the delayed AGC output lead is grounded through J1002D. When the RECEPTION control is set at A1 BROAD, A1 SHARP, or A2 the delayed AGC line is grounded by S1003 and gain is controlled by the i-f section of the GAIN control, R251B, R451B, or R651B, on the front panel.