Dr. Ulrich Rohde described in one of his articles (QST ?) a novel
product
detector based on CD4066 MOS-switch, which is supposed to have a
superior
performance compared to other types. I have tried the schematic and
found the distortion quite unacceptable.

I have not found any other reference to this type of product detector
and may have misunderstood the cocept somehow. Therefore I would like to
know if this idea is still alive and/or if somebody has any experience
of it. Otherwise I will rely on either DMB or MOSFET in my homebrew
receiver which is intended to be an advanced .
project.

I have already successfully constucted the front end with Fairchild
FST3125
switching mixer followed by a strong postmix amp, 12-pole xtal filter
and the following if-stages. It would a shame to destroy the whole thing
with an inferior detector/af-portion when I am trying accomplish
something better than my previous
design which is heavily based on the W7ZOI Progressive receiver.

73 de Heikki

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??

Joe
W3JDR


"Heikki Ahola" wrote in message
...
Dr. Ulrich Rohde described in one of his articles (QST ?) a novel
product
detector based on CD4066 MOS-switch, which is supposed to have a
superior
performance compared to other types. I have tried the schematic and
found the distortion quite unacceptable.

I have not found any other reference to this type of product detector
and may have misunderstood the cocept somehow. Therefore I would like to
know if this idea is still alive and/or if somebody has any experience
of it. Otherwise I will rely on either DMB or MOSFET in my homebrew
receiver which is intended to be an advanced .
project.

I have already successfully constucted the front end with Fairchild
FST3125
switching mixer followed by a strong postmix amp, 12-pole xtal filter
and the following if-stages. It would a shame to destroy the whole thing
with an inferior detector/af-portion when I am trying accomplish
something better than my previous
design which is heavily based on the W7ZOI Progressive receiver.

73 de Heikki

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??

Joe
W3JDR


"Heikki Ahola" wrote in message
...
Dr. Ulrich Rohde described in one of his articles (QST ?) a novel
product
detector based on CD4066 MOS-switch, which is supposed to have a
superior
performance compared to other types. I have tried the schematic and
found the distortion quite unacceptable.

I have not found any other reference to this type of product detector
and may have misunderstood the cocept somehow. Therefore I would like to
know if this idea is still alive and/or if somebody has any experience
of it. Otherwise I will rely on either DMB or MOSFET in my homebrew
receiver which is intended to be an advanced .
project.

I have already successfully constucted the front end with Fairchild
FST3125
switching mixer followed by a strong postmix amp, 12-pole xtal filter
and the following if-stages. It would a shame to destroy the whole thing
with an inferior detector/af-portion when I am trying accomplish
something better than my previous
design which is heavily based on the W7ZOI Progressive receiver.

73 de Heikki

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

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

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

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