To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

Terry

Maybe all this is meaningful only when referring to really high-end
receivers. All I know is that I sometimes hear annoying distortion
when listening to a reasonable-strength SWBC station, and hitting
the "Sync" button on the Grundig 800 or the Sony 2010 makes it
stop. That increases my listening enjoyment. What more can I ask of it?

Will

wrote:
To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

Terry

Will wrote:
Maybe all this is meaningful only when referring to really high-end
receivers. All I know is that I sometimes hear annoying distortion
when listening to a reasonable-strength SWBC station, and hitting
the "Sync" button on the Grundig 800 or the Sony 2010 makes it
stop. That increases my listening enjoyment. What more can I ask of it?

Will


I own several receivers, R2000, R390, R392 and a DX398. I currently
have a AOR7030+. From some experiments last summer to the
present I found that the "standard", and all too common, diode
detector wasn't the best choice for detection. In my quest for a
better detector I found many non obvious "things" can mess up
intelligibility. I built a micro power transmitter, with a high quality
modulator, driven by a MP3 player that loops a random set of
words that can be easily confussed. Copy/Coffee etc.

By reducing the transmitter power level to the minimum level where
I could achive 80% intelligibility I was pleasantly shocked to find
that by using better detectors I could drop the power from the
transmitter by up to ~12dB. The major weakness was, while my
signal is far enough away to insure my dB readings are reasonably
accurate, I could only deal with QRM/QRN impossed on top of my
test signal, I couldn't duplicate or even simulate the deep fades
caused by multipath.

I went to considerable trouble to design, test and redesign an
outboard detector complete with better IF filters.

I was somewhat satisified with the results, but I had been lead to
believe that a synch detector was an almost magical device that
could eliminate or reduce the unintelligibility caused by bad selective

fading. DL's experiments and observations showed me that perhaps
I had mad false assumptions.

At the time when I started I had the AOR for a couple of weeks and did
not have time to completly evaluate the AMSD capacity to moderate
the effects of deep fades.

Since our friend had to ship her AOR back to England for repair, and
since she now is living in New Zealand, she had it shipped to me for
a "check out". I have had enough experience with my AMSD to be
able to appreciate the AOR a little better. While it is not perfect I
would gladly give my left nu, er left foot for one.

But an AMSD is not a cure all. The better filters, better audio etc
make the AOR a joy to use. The multi-level control scheme makes
it a royal PITA! But even the AOR showed clear benifit from DLs
ELPAF. For a more pedestrian receiver like the R2000, a better
detector, see my posts for links, with a better audio chain, better
IF filter and the DL ELPAF my R2000 can dig out 99% of what the
AOR receives. True the AOR 7030+ has a much better choice of
filters(drool drool), and the audio chain is quiter then anything I
have
been able to yet build, but for less then 50$, I am a good scrounger
and love to trade, I have improved my R2000 significantly.

And we use a DX398 for mini DXpeditions and with a tighter IF filter
and
an add on DL ELPAF the radio is many times better then a stock version.

I bought a used DX-398, some what scuffed but I paid $5 at a local
"Good
Will" thrift store, and plan on adding a simple "improved AM detector",
with
a better(tighter) IF filter and see if the work is worth the effort.

One thing to keep in mind is that Dallas Lankford is a serious MW DXer.

And on the MW band every station you tune in will have one or more weak

stations underneath as it were, and during a deep fade, the "weaker"
station might become strong enough to upset an AMSD more then most
of us will experience on "most" HF/SW signals.

I brought the orignal thread up because I found the ELPAF really made
some signals more intelligible and made others much more injoyble to
listen to.

If I knew a year ago what I now know I might not have gone to the
trouble
to build the outboard IF strip with AMSD etc. Then again I likely would

have gone ahead in my typical bull headed way.

The "funny" thing is I am more into utility listening, where there is
very
little AM to benifit from a AMSD. Of course the Synch detector chip,
Analog Devices AD607, is a very good SSB product detector.

Given the lack of posts and threads that have ANYTHING to do with
SW, or indeed radio at all, I felt a need to pass this information on
to those who might find it as usefull as I have.


Terry

If he's so mystified at the performance of various sync detectors than
perhaps his simulated testing is the problem. Even double sided sync
detectors that I have used greatly reduce distortion during fades (as they
should), including the older SW8, the R8 and R8A. Better 'selectable
sideband' sync detectors such as the NRD-535D, the newer SW8 and R8B, and
the RX-350 sigficantly reduce distortion AND help with adjacent channel
inteference. I am equally mistified as to why he can't hear the difference.
Every time I fire up the R-388 or the Hammarlund, I immediately notice the
distortion during fading because I usually don't have to put up with it.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html

wrote in message
ups.com...
To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

Terry

I think the gent has a solution that is looking for a problem.


Brian Denley wrote:
If he's so mystified at the performance of various sync detectors than
perhaps his simulated testing is the problem. Even double sided sync
detectors that I have used greatly reduce distortion during fades (as they
should), including the older SW8, the R8 and R8A. Better 'selectable
sideband' sync detectors such as the NRD-535D, the newer SW8 and R8B, and
the RX-350 sigficantly reduce distortion AND help with adjacent channel
inteference. I am equally mistified as to why he can't hear the difference.
Every time I fire up the R-388 or the Hammarlund, I immediately notice the
distortion during fading because I usually don't have to put up with it.

--
Brian Denley
http://home.comcast.net/~b.denley/index.html

wrote in message
ups.com...
To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

Terry

wrote in message
ups.com...

Will wrote:
Maybe all this is meaningful only when referring to really
high-end
receivers. All I know is that I sometimes hear annoying distortion
when listening to a reasonable-strength SWBC station, and hitting
the "Sync" button on the Grundig 800 or the Sony 2010 makes it
stop. That increases my listening enjoyment. What more can I ask
of it?

Will


::snippage::

Given the lack of posts and threads that have ANYTHING to do with
SW, or indeed radio at all, I felt a need to pass this information
on
to those who might find it as usefull as I have.

Terry, I am consistently impressed by your thoroughness
and attention to detail. Keep up the good work.

--Mike L.

Hello,

I do not know Dallas Lankford's e-mail address so I should like to make
a comment here in the hope that he will see it (or that someone will
forward it to him).

As a "program listener," I disagree with his overall assessment of
synchronous detection circuits in general as I find that even the
weakest one I own (on the Sony ICF-SW7600GR) is far more useful than
not in making SW (and MW) signals more intelligible and listenable.
However, be that as it may, and we are all entitled to our opinions of
this circuit (and it is obvious that Mr. Lankford knows what he is
doing so I accept and respect his opinion), I must strongly disagree
with his assessment of the AOR AR7030 Plus' synchronous detection
circuit and his characterization of it as being "unacceptable."

He is quite right, of course, when he states that the AOR's sync
circuit often will not lock by itself on a VERY weak AND fast-fading
signal (is there any sync circuit that will?) but there is, in fact, a
"trick" to get it to do so.

I control my AR7030 Plus with Jan Arkesteijn's "RxWings" - a free
computer-control program. As is known, when using the AOR with the
remote or the radio's tuning dial, and changing stations, the sync
temporarily turns off and then relocks (or attempts to) on the new
tuned frequency. If tuning to the type of signal mentioned by Mr.
Lankford, the radio will not re-lock, but, if using "RxWings," the sync
circuit never shuts off.

In other words, all one has to do is to engage the sync lock on any
relatively strong signal and then tune, via "RxWings" to the desired
(very weak and fading) station. The sync circuit will maintain lock.
Indeed, in over two years of ownership, once locked, my particular unit
has NEVER lost lock under any circumstances whatsoever! (Of course I
use the AUTO setting exclusively with the sync.)

I believe that the AOR AR7030 Plus synchronous detection circuit is a
superb one and is one that greatly enhances the listening experience.
At least it does for me!

I hope this is of some use to all in general and to Mr. Lankford in
particular. I also want to thank Mr. Lankford for his excellent and
thought-provoking article. I hope to see more along these lines from
him.

Best,

Joe

wrote:
To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

Terry

Joe Analssandrini wrote:
Hello,

I do not know Dallas Lankford's e-mail address so I should like to make
a comment here in the hope that he will see it (or that someone will
forward it to him).

As a "program listener," I disagree with his overall assessment of
synchronous detection circuits in general as I find that even the
weakest one I own (on the Sony ICF-SW7600GR) is far more useful than
not in making SW (and MW) signals more intelligible and listenable.
However, be that as it may, and we are all entitled to our opinions of
this circuit (and it is obvious that Mr. Lankford knows what he is
doing so I accept and respect his opinion), I must strongly disagree
with his assessment of the AOR AR7030 Plus' synchronous detection
circuit and his characterization of it as being "unacceptable."

He is quite right, of course, when he states that the AOR's sync
circuit often will not lock by itself on a VERY weak AND fast-fading
signal (is there any sync circuit that will?) but there is, in fact, a
"trick" to get it to do so.

I control my AR7030 Plus with Jan Arkesteijn's "RxWings" - a free
computer-control program. As is known, when using the AOR with the
remote or the radio's tuning dial, and changing stations, the sync
temporarily turns off and then relocks (or attempts to) on the new
tuned frequency. If tuning to the type of signal mentioned by Mr.
Lankford, the radio will not re-lock, but, if using "RxWings," the sync
circuit never shuts off.

In other words, all one has to do is to engage the sync lock on any
relatively strong signal and then tune, via "RxWings" to the desired
(very weak and fading) station. The sync circuit will maintain lock.
Indeed, in over two years of ownership, once locked, my particular unit
has NEVER lost lock under any circumstances whatsoever! (Of course I
use the AUTO setting exclusively with the sync.)

I believe that the AOR AR7030 Plus synchronous detection circuit is a
superb one and is one that greatly enhances the listening experience.
At least it does for me!

I hope this is of some use to all in general and to Mr. Lankford in
particular. I also want to thank Mr. Lankford for his excellent and
thought-provoking article. I hope to see more along these lines from
him.

Best,

Joe


Pete's Analog Devices AD607 based receivert will track down below
the audible noise floor. On MW the AD607 is generally "better" as in
"will
track rapidly fading stations with multiple stations in the back ground
with
no, or very few growls" then AOR's in any position.

However the "improved AM detector" at
http://www.amwindow.org/tech/htm/alowdisdet.htm is about 95%+
as effective and never growls. And is a lot easier to build!

Thanks for the name of a control program for The AOR, since I will only
have it
for another 3 or 4 weeks, I didn't want to spring for a "real", as in
commercial,
software. I didn't realise the AOR acted differently under PC control
then
the local controls.

If I ever win the lottery, unlikely as I don't buy tickets, I would
love to buy at
least one of every major AMSD equiped radio, a Kiwa MAP, and the
Sherwood
SE-3.

I have come the conclussion that a good IF filter makes more difference
then the detector.

Terry

wrote:
To add more fuel ot the fi
http://www.kongsfjord.no/dl/Audio/AM%20Synchronous%20Detector%20Experiences.pdf

The date on this addition is July 19, and either it was just placed in
the archive, or I just noticd it. At least it gives us something to
think about.

The problem with synchronous detectors is not that they aren't a good
idea; it's that they're a hard to do well enough to improve upon a good
envelope detector. Even when they work well, they expose poor
performance in the rest of the receiver.

I built the 1993 Synchronous detector from the QST article. It works
well on groundwave signals. However, it's very hard to keep the thing
locked when going through a fade. To stay locked, one needs more
drastic measures. A Costas loop circuit could do this. So could a
second harmonic IF dedicated to locking up on the carrier.

Another major problem is the pathetic dynamic range one finds in typical
IF sections. Many engineers use AGC to keep things within a fairly
narrow range. The dynamic range of two in-band carriers isn't something
typically measured in most receivers. Good receivers have in-band
dynamic ranges in the 80 dB range.

A good in-band dynamic range, a clean LO, and a solid synchronous
detector design will sound very good. Anything less will not be much of
an improvement over conventional envelope detectors. This guy happened
to pick the cheaper designs.

It's as if he's passing judgment on all sushi by eating the cheap, less
than fresh stuff.

DE AB3A

wrote:
Joe Analssandrini wrote:
Hello,

I do not know Dallas Lankford's e-mail address so I should like to make
a comment here in the hope that he will see it (or that someone will
forward it to him).

As a "program listener," I disagree with his overall assessment of
synchronous detection circuits in general as I find that even the
weakest one I own (on the Sony ICF-SW7600GR) is far more useful than
not in making SW (and MW) signals more intelligible and listenable.
However, be that as it may, and we are all entitled to our opinions of
this circuit (and it is obvious that Mr. Lankford knows what he is
doing so I accept and respect his opinion), I must strongly disagree
with his assessment of the AOR AR7030 Plus' synchronous detection
circuit and his characterization of it as being "unacceptable."

He is quite right, of course, when he states that the AOR's sync
circuit often will not lock by itself on a VERY weak AND fast-fading
signal (is there any sync circuit that will?) but there is, in fact, a
"trick" to get it to do so.

I control my AR7030 Plus with Jan Arkesteijn's "RxWings" - a free
computer-control program. As is known, when using the AOR with the
remote or the radio's tuning dial, and changing stations, the sync
temporarily turns off and then relocks (or attempts to) on the new
tuned frequency. If tuning to the type of signal mentioned by Mr.
Lankford, the radio will not re-lock, but, if using "RxWings," the sync
circuit never shuts off.

In other words, all one has to do is to engage the sync lock on any
relatively strong signal and then tune, via "RxWings" to the desired
(very weak and fading) station. The sync circuit will maintain lock.
Indeed, in over two years of ownership, once locked, my particular unit
has NEVER lost lock under any circumstances whatsoever! (Of course I
use the AUTO setting exclusively with the sync.)

I believe that the AOR AR7030 Plus synchronous detection circuit is a
superb one and is one that greatly enhances the listening experience.
At least it does for me!

I hope this is of some use to all in general and to Mr. Lankford in
particular. I also want to thank Mr. Lankford for his excellent and
thought-provoking article. I hope to see more along these lines from
him.

Best,

Joe


Pete's Analog Devices AD607 based receivert will track down below
the audible noise floor. On MW the AD607 is generally "better" as in
"will
track rapidly fading stations with multiple stations in the back ground
with
no, or very few growls" then AOR's in any position.

However the "improved AM detector" at
http://www.amwindow.org/tech/htm/alowdisdet.htm is about 95%+
as effective and never growls. And is a lot easier to build!

Those precision diode circuits date back to when op-amps were
expensive. When you need such a circuit on a chip (where floating
diodes don't come easy), you simply switch between an inverted and
uninverted signal path using analog switches. A comparator controls the
switching. It's an extremely high linearity design since no diodes are
in the signal path. It's similar to a sychronous rectifier used in
power supply design.





Thanks for the name of a control program for The AOR, since I will only
have it
for another 3 or 4 weeks, I didn't want to spring for a "real", as in
commercial,
software. I didn't realise the AOR acted differently under PC control
then
the local controls.

If I ever win the lottery, unlikely as I don't buy tickets, I would
love to buy at
least one of every major AMSD equiped radio, a Kiwa MAP, and the
Sherwood
SE-3.

I have come the conclussion that a good IF filter makes more difference
then the detector.

Terry