Figure 7.9 Ratio Detector. On the left is a transistor. This is the last IF amplifier which is most likely a limiter. The base and emitter are not shown as connected to anything. The collector connects to the top of the primary of the detector transformer. The bottom of the primary connects to Vcc. The primary is tuned to the center frequency of the IF by a variable capacitor. The secondary winding is center tapped and is also tuned by a variable capacitor. The tertiary winding is not tuned and has its upper end connected to the secondary center tap inside the transformer can. The bottom of the tertiary winding connects to one end of a 68 ohm resistor. The other end connects to one end of a 330 pf capacitor. The top of the secondary connects to the anode of a diode, D1. The bottom of the secondary connects to the cathode, that's right, cathode, of D2. The cathode of D1 connects to one end of another 330 pf capacitor. The anode of D2 connects to a third 330 pf capacitor. The free ends of these two 330 pf capacitors are connected together and go to the junction of the 68 ohm resistor and the 330 pf capacitor. This point also goes to an arrow indicating an output signal is taken from this point. It is labeled M P X which means multiplex. This point also goes to one end of a 75 k ohm resistor. The other end of this resistor goes to ground through a 0.001 u f capacitor. The junction of the 75 k and 0.001 u f goes to another arrow output labeled Audio, meaning monophonic audio. The junction of the cathode of D1 and the 330 pf capacitor connects to one end of a 2.2 k ohm resistor. The other end of the 2.2 k ohm goes to ground through a 10 k ohm resistor. The junction of the anode of D2 and the 330 pf capacitor goes to ground through a 10 k ohm resistor. The junction of the 2.2 k and 10 k goes to the positive end of a 5 u f electrolytic capacitor. The junction of the D2 anode and the 10 k resistor goes to the negative end of this capacitor. This same point goes to one end of a 47 k ohm resistor. The other end goes to an arrow output labeled AGC. End verbal description.
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