Graeme Zimmer wrote:
the synchronous AM detector is a dual-sideband detector

Some are, some aren't.

My Sony ICF-SW7600GR lets you select sidebands while in Synchro mode,
as does my homebrew DSP RX.

Selecting sideband in AM mode is most useful.

Ok it can be done but not with the circuit described in this thread
and on the referenced site.

You need two mixers and 90deg phase shifts to do it.