This is a singly balanced diode demodulator with dual carrier oscillators to be used in conjunction with an AM radio that has a 455kHz IF. The two oscillators are switched from their supply rails and their outputs are parallel coupled to demodulator.  

There is a buffer emitter follower at the IF input presenting a very low impedance to the centre of the demodulator trifilar transformer.  This further attenuates any residual carrier signal getting back to the IF input port.  The oscilloscope probe connected to the IF pin show under 1mV p-p carrier oscillator emission.  There is no discernable emission of carrier signal from the AF pins.

Supply to the buffer is also derived from the oscillator rails using diodes.  PCB size 70 x 37mm (2.75" x 1.46").

The carrier oscillators use ceramic resonators which provide excellent stability.  As it is likely the unit will be used with an AM radio that does not include a SSB bandwidth filter it is best if the oscillators are aligned for 458kHz for LSB and 452kHz for USB.

This board is recommended to be built into an RF tight enclosure with IF input PTFE feedthrough and ground terminal.  Similarly for the AF output and for +LSB & +USB terminals.