frequency shifter - BFO problems

[Christopher_List at sonymusic.com]

> I'd love to get some ideas, hints etc. what could be wrong.
> I'd always love to get some experience shared from people who already
> use frequency shifters (commerciall ones, or home built ones), if they
> also have some unsteady level when the frequency shift is near zero.

I've built the Electronotes PCC Freq. Shifter using AD633 multipliers, and
the same freq. multiplication techniques and have noticed the same problem.
In my case, I've noticed some erratic output (Voltage vs. Time) from each
multiplier near 0 Hz - even without doing and x/y comparison between the
two...

I'm afraid I don't know the answer, but I figured it might make you feel
better to know that you're not alone :)

- CList