Heikki,
I dug this issue out of the archives and looked at the circuit. I'm not
surprised that the performance is not real good. This circuit has no balance
or switching symmetry. It is a simple half-wave switch which samples the IF
at the BFO frequency. The output will have significant energy at the IF
frequency as well as the BFO frequency, and these components might be
overloading the audio amplifier.

I'd suggest something that has full-balance. You could modify the '4066
circuit to have this property if you could generate 2 opposite phases of the
IF and drive them separately into the inputs of the two '4066's. If you set
it up right, you will get very large dynamic range.

Alternatively, a traditional double balanced IC circuit such as an NE602 or
even a diode DBM will work just fine as long as there is adequate
selectivity in front of it to ensure that it is normally working with one IF
input signal.

Joe
W3JDR


"Heikki Ahola" wrote in message
...


W3JDR wrote:

Heikki,
I'm not sure exactly what this particular circuit looks like, but I
strongly
suspect it's just a balanced mixer made from 4066 analog switches. I
have
used this technique and it is quite good at low IF frequencies (a few
MHz or
less). Are you sure you have the switches biased properly? The thru-path
should be biased at about 1/2 of the 4066 DC supply voltage in order to
avoid severe signal clipping. Can you point to a link where the circuit
is
shown??


The circuit can be found in QST Nov 1992 (Recent Advances in Shortwave
Receiver
Design)! I t is unclear whether only two switches are used or if each
switch is
actually two in parallel. The biasing should be OK!

73 de Heikki