This product is kitted up as required by Spectrum Communications. 

The board is designed as an add-on demodulation of FM on any receiver that has an AM passband and 455kHz IF output and a AF input back to the volume control.  Otherwise is can be fitted inside and a switch added to for AM/FM demodulation.

The board will work with any DC supply from 9-13.5V.  It requires 20uV IF signal for full quieting though the IF output from receivers could be as high as 100mV, but that will not overload it.  The recovered audio for a signal with a modulation frequency of 1kHz and a deviation of +/-2.5KHz is typically between 200 & 300mV.

It requires a 10k linear potentiometer squelch control and would ideally be built into a box with the control and an input IF and an output AF socket and with a flying red/black lead for a bench DC supply.  The board size is 2.4 x 1.6 x 0.6" (61 x 40 x 16mm) and is offered as a ready built PCB.