Here are two circuits which include a Product Detector, an AVC circuit for those Commmand Receivers which don't have one originally, and selectable-sideband.

1) My modification of a circuit designed and published, I have no idea where, by W9QAZ and K9DUI. My original copy was a hand-drawn single-page. Click HERE for a PDF copy of my circuit.

2) The earlier circuit by W9QAZ and K9DUI. Click HERE for a PDF of this circuit.