Wolf,

Was the L.O. using 74AC74 + 74AC08 better than the simple 74 HC 107 method

?

No! I had done the 74/08 section before you produced the schematic for the
HC107. It is simpler. Is that dual-JK version fairly glitch-free?

One other note at this point. I attempted to use a CD4017B, but it just
wasn't fast enough to provide good carrier and sideband suppression. This is
definitely a project for HC or AC logic.

...and one suggestion:
To eliminate the need to adjust the offset voltage for the 4 input
opamps, simply use AC-coupling. I found this very cute to reduce the
number of trimpots to the minimum (namely zero)...

Yes, but I wondered if the switch operation would be cleaner without the
charging and discharging of the caps. I can put some in there and see if it
makes a difference. Stay tuned! Available playing time is limited this
week...

John