The AM Forum

This link describes a fully self-contained, on-board product detector for the 51J series.  This product dtector is a self-contained plug-in accessory  for these receivers.  Comes full built up.   

PD3 Product Detector
http://www.treetopcircuits.com/pmwiki/pmwiki.php/Main/PD3

From the manual...

"The PD3 Product Detector (Fig. 1) from Treetop Circuits is designed specifically as an accessory for the Collins R-388 and 51-J series receivers. It provides enhanced performance in SSB and CW modes. Performance in AM mode is largely unchanged. A 12-volt DC supply for the receiver’s muting relay is incorporated as an added convenience.

The unit plugs into the radio in place of the detector/AVC tube V110 (Fig. 2), and most connections are made through the tube socket. In addition, two wires are connected from the PD3 to the radio, three components are removed, and one wire moved. With the PD3 installed, all controls operate as before, but performance in SSB and CW modes is markedly improved.

To achieve this improved performance, the PD3 replaces the diode detector with a high-level product detector, and provides a fast-attack slow-return dual-time-constant AVC circuit patterned after late-production KWM-2’s. These circuits are automatically switched in when the receiver’s BFO is turned on. With the BFO turned off, AM detector and AVC circuits which closely mimic the original circuits are switched in.

The PD3 comes as a PC board, ready to install and operate."

It's only $60.00

the automatic switching feature is neat... but it is soylent state...

interesting idea.

                           _-_-bear