Gate Leak Detector. On the left is an air wound transformer. The number of loops in the symbol indicates that the primary has more turns than the secondary. The coil is labeled Hammond P dash C70 dash eh. The upper end of the primary connects to an antenna and the lower end connects to earth ground and circuit common. The lower end of the secondary also connects to circuit common. The upper end connects to the top of a variable capacitor which is labeled 30 to 365 p f. The lower end of the variable capacitor connects to circuit common. The upper end of the coil and variable capacitor connect to the parallel combination of a resistor and capacitor. The resistor is a 2.7 meg ohm and the capacitor is a 27 p f. The other end of the R C parallel combination goes to the gate of an F E T, M P F 1 0 2. The source of the fet goes to common. The drain of the fet goes through a 1 k ohm resistor to plus 12 volts. The drain also goes through a 0.1 u f capacitor to common. The drain also goes through a 1 u f capacitor to the center conductor of the output jack. The outer side of the jack goes to common. The end of the 1 u f cap the connects to the drain is marked with a plus sign. This completes the verbal description of the schematic diagram.
The oscilloscope screen shot shows a normal A M modulated wave near the top of the screen. The modulating signal is a sine wave. The modulation percentage is 90%. Near the bottom of the screen is the recovered audio wave. The positive peak occurs at the minimum amplitude of the envelope of the AM wave. It is clear that the recovered audio wave is distorted. The positive peak . is more rounded and broader than the negative peak which is narrower. There is also some carrier leak through showing on the negative peak. The scale setting for the A M wave is 200 mV per division and for the recovered audio is 20 mV per division. This completes the verbal description of the oscilloscope display.