Q1(2N3904) is oscillator using XTAL that connecting to Q2 with C3(82pF). Q2 is mixer between the frequency Q1 and input from antenna. There is the bandpass filter between antenna and Q2 collector. The bandpass filter is C5/C7 (820pF) and L3 (22 uF). Frquency is 1/(2*pi SQRT(LC)) that is7.445 MHz. There is the capacitance C5 (0.01uF) between antenna and Q2 collector to cut the DC effect between Q2 collector and antenna.
Mixer output appears at the Q2 emitter. It's connected to LM386 through C8 (0.1uF). This is the direct conversion receiver, therefore, LM386 should amplify audio freqency with the voltage gain(46dB). D1(1N914) is a diode to prevent current follow to pin 6 on LM386. For pin6 on LM386, DC at +9V DC is supplied through R1 1KOhm. C10 10uF is the purpose to be stabilized at +9V DC. There is 4-7V DC which depends on the current amount to pin 6 on LM386.
C4 is the simple low pass filter beyond the audio frequency. R4 keeps the DC voltage for the Q2 emittor.
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