This is a first draft. Critique, corrections, and suggestions for
improvement and inadvertently omitted information welcome.





AM Synchronous Detector Review: Sony ICF-2010 vs RL Drake R8B

Two terrific SWL receivers with comparable performance up to a point.

Operating technique differs between these two synchronous detectors.
Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome phase distortion introduced
in the incoming signal by dynamics and irregularities in the Earth's
ionosphere and magnetosphere. The restoration of the signal's phase
relationship results in a significant increase in readability. Both
receivers' synchronous detectors are enabled by pressing the
respective 'Sync' button. The difference in their operation occurs
when adjusting the other signal enhancing function of this remarkable
AM detector.

One of the primary tools employed by the radio operator is the
selection of bandwidth appropriate to the current reception
conditions. Narrowing the bandwidth is effective in removing two
additional types of signal degrading effects: atmospheric noise, and
adjacent channel splatter and heterodyne. T?he AM synchronous
detector provides the means to continue the exploit of this bandwidth
narrowing philosophy significantly by providing the means to further
restrict the detection envelope to only a single sideband of the
inherently double-sideband AM signal

This 50% reduction in the significant portion of the incoming signal
permits the bandwidth to be further narrowed to reduce the amount of
noise being demodulated, thus improving the signal to noise ratio. It
also permits the operator to choose the sideband experiencing the
lessor adjacent frequency interference, further increasing the signal
to noise ration.

With the Sony ICF-2010, the selection of which sideband on which the
detector will lock is achieved by changing the main tuning setting.
The RL Drake R8B receiver provides for selecting the sideband without
changing the position of the receiver's main tuning by pressing the
'LSB' or 'USB' buttons. To this point the effects of adjusting the
receivers results in similar enhancement of levels of signal
intelligibility. However the RL Drake R8B provides two additional
signal to noise enhancing functions: 'Passband Offset' and 'Notch.'

Drake's 'Passband Offset' control "alters the position of the
receiver's intermediate frequency (IF) passband without disturbing the
main tuning." Changing the setting of this control permits the
operator to emphasize a portion of the audio spectrum contained within
the sideband being detected. This function can further enhance the
readability significantly, and places the capability of the Drake
receiver above the Sony. But the Drake has another effective function
to even further improve the final quality of the radio signal for
listening.

Drake's 'Notch' filter provides the radio operator the ability to
remove narrow band of the audio spectrum (500-5kHz) contained in the
final signal output. It is useful to remove any steady tone that
remains such as an interfering heterodyne. Drake also provides a
multi-position Noise Blanker notably absent on the Sony.

While the Sony ICF-2010's synchronous detector provides superlative
signal clarification and intelligibility, the RL Drake R8B's ability
to enhance the most marginal of radio signals to pleasant readability,
well beyond that of the Sony, is nearly magical.

Larry Dighera wrote:


This is a first draft. Critique, corrections, and suggestions for
improvement and inadvertently omitted information welcome.





AM Synchronous Detector Review: Sony ICF-2010 vs RL Drake R8B

Two terrific SWL receivers with comparable performance up to a point.

Operating technique differs between these two synchronous detectors.
Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome phase distortion introduced
in the incoming signal by dynamics and irregularities in the Earth's
ionosphere and magnetosphere.

The distortion is caused by selective fading where the carrier is reduced in
amplitude resulting in the equivalent of an over modulated signal. It is
the effective overmodulation that results in a distorted signal when using
a peak detector.

The restoration of the signal's phase
relationship results in a significant increase in readability. Both
receivers' synchronous detectors are enabled by pressing the
respective 'Sync' button.

Rather than 'restoring the phase', you are switching from a peak detector to
a product detector which does not rely upon receiving a carrier to
demodulate the signal. A product detector has two inputs, one being the
received signal, the other being a locally generated frequency (I choose
not to say carrier). In a sync detector, the locally generated frequency is
phase locked to what remains of the received signal's carrier. (Note, by
using SSB you are doing the same thing, EXCEPT the locally generated
frequency is not locked to the incoming signal. Thus fine tuning is needed
when using SSB. I don't call this ECSS, because the you do not Exhault the
Carrier.)

The difference in their operation occurs
when adjusting the other signal enhancing function of this remarkable
AM detector.

One of the primary tools employed by the radio operator is the
selection of bandwidth appropriate to the current reception
conditions. Narrowing the bandwidth is effective in removing two
additional types of signal degrading effects: atmospheric noise, and
adjacent channel splatter and heterodyne. T?he AM synchronous
detector provides the means to continue the exploit of this bandwidth
narrowing philosophy significantly by providing the means to further
restrict the detection envelope to only a single sideband of the
inherently double-sideband AM signal

Without the sync detector one can still narrow the bandwidth to include one
sideband and the carrier.

snip

Hope this helps

craigm

My comments in-line below:


On Wed, 21 Feb 2007 20:53:41 -0600, craigm wrote
in :

Larry Dighera wrote:


This is a first draft. Critique, corrections, and suggestions for
improvement and inadvertently omitted information welcome.





AM Synchronous Detector Review: Sony ICF-2010 vs RL Drake R8B

Two terrific SWL receivers with comparable performance up to a point.

Operating technique differs between these two synchronous detectors.
Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome phase distortion introduced
in the incoming signal by dynamics and irregularities in the Earth's
ionosphere and magnetosphere.

The distortion is caused by selective fading where the carrier is reduced in
amplitude resulting in the equivalent of an over modulated signal. It is
the effective overmodulation that results in a distorted signal when using
a peak detector.

There is a reasonable definition for 'selective fading' he

http://en.wikipedia.org/wiki/Selective_fading
frequency selective fading is a radio propagation anomaly caused
by partial cancellation of a radio signal by itself — the signal
arrives at the receiver by two different paths, and at least one
of the paths is changing (lengthening or shortening). This
typically happens in the early evening or early morning as the
various layers in the ionosphere move, separate, and combine. The
two paths can both be skywave or one be groundwave.


And there is an in-depth discussion of 'selective fading' he

http://www.hard-core-dx.com/nordicdx...al/fading.html
There are two primary causes of signal fading on shortwave
multipath cancellation and polarization rotation.
...
Signals demodulated by a sync detector are not subject to
selective fading of the carrier as long as there is enough carrier
present to keep the detector locked. Long time constants on the
carrier tracking, phase locked loop allow the synchronous detector
to "fly wheel" through short carrier fades without losing lock.


[A mathematical treatise on fading is available he
http://www.mwrf.com/Articles/ArticleID/7964/7964.html ]


So, to incorporate the concept of 'selective fading' into my original
sentence, it might be re-worded thusly:

Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome audio distortion
introduced in the incoming signal by dynamics and irregularities
in the Earth's ionosphere and magnetosphere, as well as multi-path
selective fading.


The restoration of the signal's phase
relationship results in a significant increase in readability.

Rather than 'restoring the phase', you are switching from a peak detector to
a product detector which does not rely upon receiving a carrier to
demodulate the signal.

That statement seems to contradict the operation of the synchronous
detector described in the www.hard-core-dx.com article citation above.
A product detector has two inputs, one being the
received signal, the other being a locally generated frequency (I choose
not to say carrier). In a sync detector, the locally generated frequency is
phase locked to what remains of the received signal's carrier. (Note, by
using SSB you are doing the same thing, EXCEPT the locally generated
frequency is not locked to the incoming signal. Thus fine tuning is needed
when using SSB. I don't call this ECSS, because the you do not Exhault the
Carrier.)


There is an elementary discussion of detector types he
http://en.wikipedia.org/wiki/Detector_(radio)

Although the 'peak detector is not mentioned in the above article, the
'envelope detector' is, and it seems to be synonymous.

The above article defines a 'product detector' thusly:

Product detector
A product detector is a type of demodulator used for AM and SSB
signals. Rather than converting the envelope of the signal into
the decoded waveform like an envelope detector, the product
detector takes the product of the modulated signal and a local
oscillator, hence the name. This can be accomplished by
heterodyning. The received signal is mixed, in some type of
nonlinear device, with a signal from the local oscillator, to
produce an intermediate frequency, referred to as the beat
frequency, from which the modulating signal is detected and
recovered.


So, rewriting my original sentence:

The restoration of the signal's phase relationship results in a
significant increase in readability.

to encompass the notion of product detection might look like this:

The restoration of the incoming signal's original carrier
amplitude results in a significant increase in readability.

Is that a correct statement?


Both receivers' synchronous detectors are enabled by pressing the
respective 'Sync' button. The difference in their operation occurs
when adjusting the other signal enhancing function of this remarkable
AM detector.

One of the primary tools employed by the radio operator is the
selection of bandwidth appropriate to the current reception
conditions. Narrowing the bandwidth is effective in removing two
additional types of signal degrading effects: atmospheric noise, and
adjacent channel splatter and heterodyne. The AM synchronous
detector provides the means to continue the exploit of this bandwidth
narrowing philosophy significantly by providing the means to further
restrict the detection envelope to only a single sideband of the
inherently double-sideband AM signal

Without the sync detector one can still narrow the bandwidth to include one
sideband and the carrier.

I suppose that's true, although I hadn't appreciated it until you
pointed it out.

So, this sentence:

The AM synchronous detector provides the means to continue the
exploit of this bandwidth narrowing philosophy significantly by
providing the means to further restrict the detection envelope to
only a single sideband of the inherently double-sideband AM signal

could be re-written to remove the exclusivity implied like this:

The AM synchronous detector provides an additional means to
continue the exploit of this bandwidth narrowing philosophy
significantly by providing an additional means to further narrow
the detection envelope to only a single sideband of the inherently
double-sideband AM signal

Better?

snip

Hope this helps

craigm

Craig,

I sincerely appreciate your help in pointing out inaccuracies and
educating me about the technical aspects of the use of synchronous
detectors. If you have further critique, or issues with my proposed
changes, please continue.

Larry Dighera wrote:




My comments in-line below:

ditto



On Wed, 21 Feb 2007 20:53:41 -0600, craigm wrote
in :

Larry Dighera wrote:


This is a first draft. Critique, corrections, and suggestions for
improvement and inadvertently omitted information welcome.





AM Synchronous Detector Review: Sony ICF-2010 vs RL Drake R8B

Two terrific SWL receivers with comparable performance up to a point.

Operating technique differs between these two synchronous detectors.
Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome phase distortion introduced
in the incoming signal by dynamics and irregularities in the Earth's
ionosphere and magnetosphere.

The distortion is caused by selective fading where the carrier is reduced
in amplitude resulting in the equivalent of an over modulated signal. It
is the effective overmodulation that results in a distorted signal when
using a peak detector.

There is a reasonable definition for 'selective fading' he

http://en.wikipedia.org/wiki/Selective_fading
frequency selective fading is a radio propagation anomaly caused
by partial cancellation of a radio signal by itself — the signal
arrives at the receiver by two different paths, and at least one
of the paths is changing (lengthening or shortening). This
typically happens in the early evening or early morning as the
various layers in the ionosphere move, separate, and combine. The
two paths can both be skywave or one be groundwave.


And there is an in-depth discussion of 'selective fading' he

http://www.hard-core-dx.com/nordicdx...al/fading.html
There are two primary causes of signal fading on shortwave
multipath cancellation and polarization rotation.
...
Signals demodulated by a sync detector are not subject to
selective fading of the carrier as long as there is enough carrier
present to keep the detector locked. Long time constants on the
carrier tracking, phase locked loop allow the synchronous detector
to "fly wheel" through short carrier fades without losing lock.


[A mathematical treatise on fading is available he
http://www.mwrf.com/Articles/ArticleID/7964/7964.html ]


These describe how selective fading occurs, but you need to understand the
effect of selective fading on a peak(or envelope) detector.



So, to incorporate the concept of 'selective fading' into my original
sentence, it might be re-worded thusly:

Because a synchronous detector is phase-locked on the station's
carrier frequency, it is able to overcome audio distortion
introduced in the incoming signal by dynamics and irregularities
in the Earth's ionosphere and magnetosphere, as well as multi-path
selective fading.

But, no, it is the change in the detector that clears up the distortion. The
addition of using a phase locked signal in the product detector is that it
is 1) much easier to tune, 2) frequency locked to prevent unwanted howling
and other distortion products 3) phase locked to get the best results from
the product detector.



The restoration of the signal's phase
relationship results in a significant increase in readability.

Rather than 'restoring the phase', you are switching from a peak detector
to a product detector which does not rely upon receiving a carrier to
demodulate the signal.

That statement seems to contradict the operation of the synchronous
detector described in the www.hard-core-dx.com article citation above.

You'll have to be more specific, I did not see real details on the operation
of the sync detector on the page, or in the snippet above. The key thing is
how the detector works. Note the page also indicates the use of SSB mode.
The difference between SSB and synchronous modes is how the singal going to
the product detector is generated. One is phase locked, one is not.



A product detector has two inputs, one being the
received signal, the other being a locally generated frequency (I choose
not to say carrier). In a sync detector, the locally generated frequency
is phase locked to what remains of the received signal's carrier. (Note,
by using SSB you are doing the same thing, EXCEPT the locally generated
frequency is not locked to the incoming signal. Thus fine tuning is needed
when using SSB. I don't call this ECSS, because the you do not Exhault the
Carrier.)


There is an elementary discussion of detector types he
http://en.wikipedia.org/wiki/Detector_(radio)

Although the 'peak detector is not mentioned in the above article, the
'envelope detector' is, and it seems to be synonymous.

The above article defines a 'product detector' thusly:

Product detector
A product detector is a type of demodulator used for AM and SSB
signals. Rather than converting the envelope of the signal into
the decoded waveform like an envelope detector, the product
detector takes the product of the modulated signal and a local
oscillator, hence the name. This can be accomplished by
heterodyning. The received signal is mixed, in some type of
nonlinear device, with a signal from the local oscillator, to
produce an intermediate frequency, referred to as the beat
frequency, from which the modulating signal is detected and
recovered.


So, rewriting my original sentence:

The restoration of the signal's phase relationship results in a
significant increase in readability.

to encompass the notion of product detection might look like this:

The restoration of the incoming signal's original carrier
amplitude results in a significant increase in readability.

Is that a correct statement?

No, 1) you are not restoring the carrier and applying it to a peak detector.
You are generating a new signal that is locked to the original carrier and
applying it as one input to the product detector. 2) The readability
improvement comes strictly from the product detector. This is why many just
use SSB mode on their receiver.



Both receivers' synchronous detectors are enabled by pressing the
respective 'Sync' button. The difference in their operation occurs
when adjusting the other signal enhancing function of this remarkable
AM detector.

One of the primary tools employed by the radio operator is the
selection of bandwidth appropriate to the current reception
conditions. Narrowing the bandwidth is effective in removing two
additional types of signal degrading effects: atmospheric noise, and
adjacent channel splatter and heterodyne. The AM synchronous
detector provides the means to continue the exploit of this bandwidth
narrowing philosophy significantly by providing the means to further
restrict the detection envelope to only a single sideband of the
inherently double-sideband AM signal

Without the sync detector one can still narrow the bandwidth to include
one sideband and the carrier.

I suppose that's true, although I hadn't appreciated it until you
pointed it out.

So, this sentence:

The AM synchronous detector provides the means to continue the
exploit of this bandwidth narrowing philosophy significantly by
providing the means to further restrict the detection envelope to
only a single sideband of the inherently double-sideband AM signal

could be re-written to remove the exclusivity implied like this:

The AM synchronous detector provides an additional means to
continue the exploit of this bandwidth narrowing philosophy
significantly by providing an additional means to further narrow
the detection envelope to only a single sideband of the inherently
double-sideband AM signal

Better?

Better, but maybe pointless as the amount of bandwidth reduction you can
achieve with or without the sync detector is about the same.


snip

Hope this helps

craigm

Craig,

I sincerely appreciate your help in pointing out inaccuracies and
educating me about the technical aspects of the use of synchronous
detectors. If you have further critique, or issues with my proposed
changes, please continue.

There is a web page which describes the effect selective fading has on a
peak/envelope detector. I can't find the link, but it does clarify the
nature of the biggest contributer to distortion with selective fading.

Hope this helps.

craigm

Interesting discussion. Just out of curiosity:

Is the sync detector on the Sony 2010 the same
circuit that is used on the currently-available
Sony ICF-7600GR? Or, since that latter has a
switch-selectible USB/LSB that applies to both
the SSB and Sync selections on the tuning-method
switch, is it more like the R8's? Or something
completely different?

73, Will

Will wrote:

Interesting discussion. Just out of curiosity:

Is the sync detector on the Sony 2010 the same
circuit that is used on the currently-available
Sony ICF-7600GR?

Will, they both use custom Sony ICs. However, they are different designs.


Or, since that latter has a
switch-selectible USB/LSB that applies to both
the SSB and Sync selections on the tuning-method
switch, is it more like the R8's? Or something
completely different?

Without details on the internals of the Sony IC, I don't know. I have been
unable to find specific information on the web.

Given their behavior, I would expect that Sony design to be similar to
Drake's. The phasing method of side band selection has been around for
years.



73, Will

craigm

On Fri, 23 Feb 2007 21:20:11 -0600, craigm wrote
in :

Without details on the internals of the Sony IC, I don't know.

You'll find some information on the Sony ICF-2010 sync circuit he

http://user.netonecom.net/~swordman/...tWaveRadio.htm
An 8-page article called "Synchronous Detection of AM Signals:
What is it and how does it work?" appeared in the September, 1992
QEX magazine. It has several pages of the theory of amplitude
modulation and then goes into the demodulation. The circuit uses
the Sony CX-857 stereo decoder and PSN phasing amplifier chips
that are used in the "famous" Sony ICF-2010 synchronous detector.
The author of the article, Mike Gruber WA1SVF, an ARRL Laboratory
EMC/RFI Engineer, reports that Steve Johnston, WD8DAS sells a kit
for building it and has more information on his web site at
http://www.qsl.net/wd8das/syncinfo.txt. WD8DAS also has a copy of
a 2-page review from the October, 1994 issue of Electric Radio
magazine. I have received permission from the ARRL to post a
scanned copy of the article.

Reprinted with permission from September 1992 QEX; copyright ARRL.
Here's the link QEX 09/1992. (99k)