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Author Topic: The Sherwood SE-3 Synchronous Detector - Very Nice!  (Read 42952 times)
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steve_qix
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« on: January 20, 2009, 10:57:26 PM »

I've been testing a Sherwood Engineering SE-3 synch detector for a few days.

Having no experience with what a good synch detector can do, I am extremely impressed with the quality of the audio attainable from the unit.

For years, I've operated 75 and 160 meters at night.  The usual selective fading causes extreme distortion, even in my low distortion detectors.  However, with the synchronous detector, all of this distortion is gone !  Even in deep selective fades, the audio remains as good as ever.  That is very nice indeed.

Another thing I like about the detector is the unit's ability to quickly lock up during break-in QSOs.  The detector has an "AR" (Amateur Radio) position, which makes the detector synch up very quickly on any carrier within a few hundred cycles.  Even stations 1kHz or so away from the last station received are locked in nicely.

There are some other features such as a product detector for SSB and some settings controlling how the lock is obtained.  There is a speaker and headphone output if needed.  I connected the audio output to my usual station audio system, along with the other receivers.

I'm still getting used to the synch detector, however from what I see so far, I am rather amazed how good some of the better engineered stations really sound when the selective fade distortion is removed !

More later  Smiley

Regards,

Steve
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WBear2GCR
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« Reply #1 on: January 20, 2009, 11:24:36 PM »


Steve,

You have a Soft Rock Lite or similar, iirc??
How does that compare?

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« Reply #2 on: January 21, 2009, 07:10:43 AM »

Steve

Interesting input on the Sherwood synchronous detector product. Thanks for posting it!

I support an implication contained in Bear's question:

All of the functionality of a synchronous detector, including all of the details of the algorithms Sherwood is using (for example) to perform synchronous detection in their latest product, can be readily performed with any of the SDR implementations.

This includes the ability to switch between fast lock-in with a wide capture range for round tables, and slower lock-in with a narrower capture range for situations where there is are interfering carriers, and one is not jumping between different members of a round table.

The existing Flex Power Power SDR application (available free from Flex) employs just one set of synchronous detector parameters (one choice of loop lock in speed and capture range)... but someone will probably add a feature that makes this user selectable (equivalent to normal and round table modes).

Although the Sherwood product is nice, for less money one could buy a decent brand new desktop computer... and implement a Softrock or Softrock-like mixer to match any i.f.

[Of note, to use the Sherwood product with an i.f. that is different from 455kHz, one needs to use a mixer anyway, to convert the i.f. to 455 kHz]

Best regards
Stu
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w3jn
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« Reply #3 on: January 21, 2009, 07:29:02 AM »

My SE-3 doesn't have an AR position so I modified it to speed the lock time; I posted my modification somewhere (in the Handbook section under Receivers I believe).  Still, in a fast-breakin session with someone off frequency a KC or so you end up missing a transmission now and then.

I measured the audio distortion from it (Agilent 8935 --> GPR-90 --> SE-3 -->8935 audio in) and it was under 1% pretty much everywhere above 300 Hz at 30-100% modulation (the 8935's notch filter doesn't go below 300Hz so its internal distortion analyzer can't measure below that frequency).

The only thing I've seen that beats the SE-3 is my HP 8901A modulation analyzer that checks in at .2% distortion or thereabouts.

It's a great accessory!  I have less than zero interest in dedicating a computer to a softrock, but that is an alternative for those who are willing to deal with all the inherent hassles with booting the computer, shack space, etc.
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« Reply #4 on: January 21, 2009, 08:17:48 AM »

John, I thought the same thing until I measured 110 dB of dynamic range with Mercury. Now I can surf, send email, build projects and play radio at the same time.
The SE3 is cool, but big bucks.
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flintstone mop
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« Reply #5 on: January 21, 2009, 09:14:04 AM »

YUP for $25 and a little time with the computer I gave up on any thoughts of spending $600 for a sync detector from Sherwood.
I'm not into specs that can only be seen by test equipment.
The SoftRock and the Flex software lock-in FB for me in the break-in mode.


Fred
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Fred KC4MOP
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« Reply #6 on: January 21, 2009, 09:54:15 AM »

And there's no spectrum display with the SE-3...or ~ infinitely variable filter bandwidths...or passband tuning...or adjustable notch filter (Perseus)...etc...etc...

The other night there was a slop bucket in close up above and another AM QSO 4 or 5 kHz below. With the aid of the spectrum display one can drag the filter bandwidth and put the upper edge of the filter just above the desired carrier...removing the slop bucket. Engage the notch filter and double click on the carrier below...it's gone. Run the filter as wide as possible, select SAM and sit back and enjoy. Only takes a couple seconds to set it up. If the situation changes you see it instantly.   

The SE-3 is a nice box for what it does, however.
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WA1GFZ
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« Reply #7 on: January 21, 2009, 09:56:36 AM »

The spectrum display alone makes it worth the money. You can monitor the whole phone band without turning a knob.
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Steve - WB3HUZ
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« Reply #8 on: January 21, 2009, 12:00:23 PM »

There's always something better or more desirable for someone' taste.

As you've seen Steve, sync detection is the way to go. For years I've been convinced most AMers much effort into perfecting the audio quality of their transmitted signal without similar efforts on the receive side. Maybe the pendulum will swing more towards the center with better detectors and some people wising up to using special receive antenna and diversity reception.
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steve_qix
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« Reply #9 on: January 21, 2009, 12:29:24 PM »


Maybe the pendulum will swing more towards the center with better detectors and some people wising up to using special receive antenna and diversity reception.

I hope so!  It's such a waste to transmit a nice signal when it is immediately mangled by the receiver's poor detector and/or AGC.
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w1vtp
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« Reply #10 on: January 21, 2009, 01:22:05 PM »

Thanks for the report Steve.  As you know I'm using the computer / FlexRadio method but the end is approximately the same.  Minimal selective fade distortion, and eliminating the need for special receiver mods other than bringing out the IF to a SoftRock, mixer conbo.  Can you give out any details for your application of the Sherwood?  I know you had to accommodate for your IF freq.

I love it

Al
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steve_qix
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« Reply #11 on: January 21, 2009, 01:28:30 PM »

Thanks for the report Steve.  As you know I'm using the computer / FlexRadio method but the end is approximately the same.  Minimal selective fade distortion, and eliminating the need for special receiver mods other than bringing out the IF to a SoftRock, mixer conbo.  Can you give out any details for your application of the Sherwood?  I know you had to accommodate for your IF freq.

I love it

Al

Hi Al,

I hooked it up to my 75A3, which has an IF transformer in place of one of the mechanical filters.  In this mode, the receiver is a good AM receiver.  I wrapped a wire around the last IF amplifier tube's plate pin (yes, a tube!), and went into a 10pF capacitor, then into a piece of audio cable to the Synch. detector.  There is a pot on the detector main board to adjust the input level, if it's too high (which it was with my particular connection).

Anyway, that's how I hooked it up!   Cool

Regards,

Steve
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« Reply #12 on: January 21, 2009, 02:39:24 PM »

More response from yours truly.
  • Jay -- I don't recall your setup but it sounds like a FlexRadio
  • Steve -- Yeah, how about trying out "the other approach?"  I'd be interested in a comparison
  • I especially like the marriage of the old with the new in my case.  Not only can I slide the filter around graphically on my computer screen, adjusting the width, position but also, I can more accurately use the on-board notch filter on my OLD FT-301 and visually walk it in over the noise towards an offending heterodyne and get rid of it. 

    I also like the 10 band RX equalizer in the PowerSDR program -- I can customize the fine audio coming out y'all's great AM stations to fit my 72 year old ears.

    I DO have a problem with the lockup time in round tables if someone is 1 KC off or off the edge of the filter - I'll either get that descending tone of the lockup search and miss the first part of the station's comments or in the other case just a ssb sounding sig 'cause he's off the edge of the very sharp DSP filter

I've read Sherwood's excellent web page - they have a lot of good resource material!  Guess the only downside of the whole Sherwood experience is the cost.  They do offer some pretty good service to those who do not have the time nor inclination to DIY this excellent mode of receiving AM

I've included an attachment on how I did my setup

73 Al

* MY SDR SETUP.pdf (321.78 KB - downloaded 355 times.)
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« Reply #13 on: January 21, 2009, 02:47:41 PM »

Al...I was previously using the R-390-A / Softrock / PowerSDR...but the Perseus currently in use is an A/D right off the antenna like the Mercury or QS1R.

 
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k4kyv
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« Reply #14 on: January 21, 2009, 02:58:42 PM »

Maybe, instead of a whole software defined radio, a software defined detector, or i.f. strip and audio stage would be a good compromise.
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Steve - WB3HUZ
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« Reply #15 on: January 21, 2009, 03:08:14 PM »

That's what you have (with some other added functionality) when you hang a Softrock or other downconverter off the IF if an existing receiver and use Flex or other SW on the back end. Going this route is cheap and easy, if you already have a computer to use.


Maybe, instead of a whole software defined radio, a software defined detector, or i.f. strip and audio stage would be a good compromise.
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W3FJJ
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« Reply #16 on: January 21, 2009, 03:26:10 PM »

A feature I like to see on today's Synch Detectors, is an auto mode. Here, it knows whether
the detector is locked or not, when its not, it automatically switches to a conventional
envelope detector. This way you can tune around and it will use envelop detector, if you
stop tuning and stay with in capture range, the synch detector will lock and switch automatically
to it. 


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k4kyv
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« Reply #17 on: January 21, 2009, 03:32:44 PM »

Kind of like IBOC digital FM.  If you lose lock, it is supposed to automatically switch back to analogue.

Unfortunately, in the case of FM broadcasting, there as a slight time delay with the digital, and when reception becomes spotty and the signal rapidly switches back and forth between analogue and digital, the time differential is reported to become very annoying.

I couldn't say from personal experience because, like the case of AM stereo, I have never seen a receiver that had IBOC FM capability.
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Steve - WB3HUZ
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« Reply #18 on: January 21, 2009, 04:27:23 PM »

The IC9500 has that. Totally transparent.


A feature I like to see on today's Synch Detectors, is an auto mode. Here, it knows whether
the detector is locked or not, when its not, it automatically switches to a conventional
envelope detector. This way you can tune around and it will use envelop detector, if you
stop tuning and stay with in capture range, the synch detector will lock and switch automatically
to it. 



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W3FJJ
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« Reply #19 on: January 21, 2009, 04:46:22 PM »

The IC9500 has that. Totally transparent.


Kewl. But can they do it for less than 10 grand  please Smiley
I saw a circuit in popular electronics article from the 70's that did it, not sure if
its totally transparent.  I want to incorporate it into
my homebrew synch detector, one of these days..
Just senses error voltage off the phaselock loop, and has delay circuit and, analog
switch to switch between the envelop and synch...
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WA1GFZ
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« Reply #20 on: January 21, 2009, 05:17:36 PM »

SMOP in the sdr world.....Simple Matter of Programming
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w1vtp
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« Reply #21 on: January 21, 2009, 05:33:52 PM »

A feature I like to see on today's Synch Detectors, is an auto mode. Here, it knows whether
the detector is locked or not, when its not, it automatically switches to a conventional
envelope detector. This way you can tune around and it will use envelop detector, if you
stop tuning and stay with in capture range, the synch detector will lock and switch automatically
to it. 

Charilie  excellent point.  From my experience point of view -- the FlexPowerSDR has an odd response when manually going from Synchronsis detection AM (SAM) to AM -- it forgets where I set the filter window - usually off to one side to maximize high freq response, and centers it.  While it isn't a major problem it sure is disconcerting to see it happen.  Maybe the Flex people will correct the problem at some point.  For things to be transparent that feature of remembering where the filter was set by the operator would be important.

BTW -- I'd rather just point and click on the choice between the two choices within the program (SAM & AM) rather than have software make the decision.  Also, my choice would NOT be going between a conventional envelope detector and SAM - the straight AM detection in my FlexPowerSDR program is still miles ahead of my envelope detector.

I apologize for straying a little off the point -- the Sherwood people have some excellent resources on receivers etc.  I highly recommend visiting their web site and looking at some of their reference material.  Thanks Steve for bringing some visibility on the subject of Sync Am detection!! Smiley Smiley

73, Al
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« Reply #22 on: January 21, 2009, 05:37:12 PM »

Al,
I don't have that problem but usually just select one of the bandwidths on the display. Maybe it happens when you do variable BW??
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w1vtp
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« Reply #23 on: January 21, 2009, 05:39:10 PM »

Al,
I don't have that problem but usually just select one of the bandwidths on the display. Maybe it happens when you do variable BW??

Yes -- sometimes I slide the filter off a bit to get rid of a heterodyne but if I switch from SAM to AM it centers the filter.

Al
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« Reply #24 on: January 21, 2009, 06:21:59 PM »

Al, in power sdr..

DON"T slide the whole filter.... just the one side-band...that may help.
Though  yes, you're right, every time you switch it resets the filter to center.


The syc am in power sdr is very slow...

SDRMAXII for QS1R, remembers the filter setting for each mode...
And the Sync AM locks on very fast (less than 1/2 second)

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