Build this Universal Gilbert Cell Audio Detector for $9.
Blank PCB is available for $4.




SA612AN PDF Spec Sheet
This kit is a very typical SA612AN (NE602) audio detector mixer circuit.
It includes a MUTE circuit consisting of Q1 and Q2.
A positive voltage on the +MUTE signal line opens the audio signal path.
BFO oscillator injection is from a fundamental crystal tuned via C5
or from an external BFO.
The 5.068 crystal is included.