> Got a note from Dieter last night, who saw these listings and he
> went into the theory behind the Shifter and how it cancels out the
> second sideband to isolate the sum and difference. Much as I've
> always heard its done, by [hase cancellation using the 90
> degree output of a quadrit. oscillator. It's a very complex circuit.

Yes, even one look at the board tells you this, and having traced most
of it out, you are not left in much doubt! Since I haven't totally
fathomed it out myself yet, I'd quite like to see the explanation too,
so if you *are* listening Dieter and would care to forward your
response to me also, I'd be most grateful!

Tim

[The views expressed above are entirely those of the writer and do not
represent the views, policy or understanding of any other person or
official body.]