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simple synchronous detector?
Has anyone implemented a simple sync detector that uses as few parts as
possible? Thanks Pete |
I think that "as few parts as possible" and "works good" are probably
somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? "Pete Beals" wrote in message ... Has anyone implemented a simple sync detector that uses as few parts as possible? Thanks Pete |
Yes most used AM stereo demodulators but those IC's might not be sold
anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? |
"Pete Beals" wrote in message ... Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? Do a search under KE9OA. Pete is developing a sync detector for use with a MW RX they are going to market. May possibly sell the sync board separately. In talking with Pete, and having built my own sync detector- few parts and sync detectors that stay locked and retrieve hi fi audio do not go together. Dale W4OP |
On Mon, 19 Jan 2004 04:18:19 -0000, Pete Beals
wrote: Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? A long long time ago one appeared in the user-contributed circuits section of Electronic Design magazine. Don't remember the name of the column but it was always good. They also used to publish circuit collections from the column every few years. Lots of clever ideas: "Build this quadraphonic stereo receiver with a single CMOS interter" is just a slight exaggeration. I remember reading the magazine up to the early 90's. Don't know what happened to them. The synchronous detector used two analog multiplier chips and as I recall was contributed by someone with a callsign. Don't remember any other details. Anybody remember the magazine and the column? Thanks and 73, Jim |
This used to be the EDN article search database. It came up, but I don't
know if it still is: http://www.reed-electronics.com/ednm...=0&rme=0&cfd=1 -- Steve N, K,9;d, c. i My email has no u's. "Jim, N2VX" wrote in message ... On Mon, 19 Jan 2004 04:18:19 -0000, Pete Beals wrote: Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? A long long time ago one appeared in the user-contributed circuits section of Electronic Design magazine. Don't remember the name of the column but it was always good. They also used to publish circuit collections from the column every few years. Lots of clever ideas: "Build this quadraphonic stereo receiver with a single CMOS interter" is just a slight exaggeration. I remember reading the magazine up to the early 90's. Don't know what happened to them. The synchronous detector used two analog multiplier chips and as I recall was contributed by someone with a callsign. Don't remember any other details. Anybody remember the magazine and the column? Thanks and 73, Jim |
What's the essence of an AM sync detector? Extract the carrier
(filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? -- Steve N, K,9;d, c. i My email has no u's. "Jim, N2VX" wrote in message ... On Mon, 19 Jan 2004 04:18:19 -0000, Pete Beals wrote: Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? A long long time ago one appeared in the user-contributed circuits section of Electronic Design magazine. Don't remember the name of the column but it was always good. They also used to publish circuit collections from the column every few years. Lots of clever ideas: "Build this quadraphonic stereo receiver with a single CMOS interter" is just a slight exaggeration. I remember reading the magazine up to the early 90's. Don't know what happened to them. The synchronous detector used two analog multiplier chips and as I recall was contributed by someone with a callsign. Don't remember any other details. Anybody remember the magazine and the column? Thanks and 73, Jim |
In article , "Jim, N2VX"
writes: On Mon, 19 Jan 2004 04:18:19 -0000, Pete Beals wrote: Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? A long long time ago one appeared in the user-contributed circuits section of Electronic Design magazine. Don't remember the name of the column but it was always good. They also used to publish circuit collections from the column every few years. Lots of clever ideas: "Build this quadraphonic stereo receiver with a single CMOS interter" is just a slight exaggeration. I remember reading the magazine up to the early 90's. Don't know what happened to them. Electronic Design is online at http://www.elecdesign.com Their newer website makes it a bit difficult to search for Design Ideas in past issues. Those probably don't go back farther than 2001 but I could be mistaken. Source code for those column pieces requiring source is available as separate text files. EDN is online at http://www.reed-electronics.com/ednmag EDN's Design Ideas go back only to 1995...but are easier to access. The synchronous detector used two analog multiplier chips and as I recall was contributed by someone with a callsign. Don't remember any other details. Anybody remember the magazine and the column? I still get both Electronic Design and EDN, plus RF Design and Microwaves & RF. Used to cut up the issues after a month or so and file them for reference...until they all got on-line and I could write them onto a CD (much easier to reference, less space). Don't recall the article or didn't bother to log it in memory as "important." :-) :-( Motorola quit a whole bunch of specialty ICs a bit ago, very few showing up on other websites. They made a nice stereo AM IC that had an automatic synchronous detection system. Not enough market demand for it. ON Semiconductor still makes a few of the old Motorola line. Len Anderson retired (from regular hours) electronic engineer person |
In article , "Steve Nosko"
writes: What's the essence of an AM sync detector? Extract the carrier (filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? -- Steve N, K,9;d, c. i My email has no u's. Essentially, yes. There's a further step, though, and that is locking a local mixing oscillator to the carrier frequency and mixing that with the whole thing. If the local mixing oscillator is in phase with the received carrier, the mixing results in just a DC component which can be removed easily. A carrier in-phase lock allows separate detection of the sidebands...which could be used to advantage such as having binaural audio modulation with AM. That also works out well for a quasi-stereo listening with any signal that is NOT binaurally modulated. The effect of hearing through such a detector's audio cannot accurately be described in words. Nearby-signal splatter can be "heard" as left or right of the desired signal. Strange sound but does allow the mind's own spatial filtering to sort-of blot out nearby interference. That quasi-stereo circuit is a lot more complicated (it's usually a typical Costas Loop with local mixing oscillator having shifts for quadrature phasing) than the direct amplify-limit-clip-the- bejeebers out of the carrier and mix that with whole works...as was done in the Motorola MC1330P 8-pin DIP IC (now obsolete but Kits&Parts as a few left). Len Anderson retired (from regular hours) electronic engineer person |
Steve's imbedded comments:
"Avery Fineman" wrote in message ... In article , "Steve Nosko" writes: What's the essence of an AM sync detector? Extract the carrier (filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? Steve N, K,9;d, c. i My email has no u's. ...locking a local mixing oscillator to the carrier frequency and mixing that with the whole thing. Ah yes! need a reliable LO. ... A carrier in-phase lock allows separate detection of the sidebands...which could be used to advantage such as having binaural audio modulation with AM. Ah yes... Back to the old three methods of generating / detecting sideband signals. Regards, Steve Lesee if he bites on that.... |
I did try to e-mail him a copy of the schematic Dale, and it bounced back to
me as undeliverable, so I am not sure what is up with his address. Oh, I did get the brackets. Thanks! Pete "Dale Parfitt" wrote in message ... "Pete Beals" wrote in message ... Yes most used AM stereo demodulators but those IC's might not be sold anymore. There must be reasonable implementations as many shortwave receivers have sync detectors. I just need one to demodulate AM. Pete I think that "as few parts as possible" and "works good" are probably somewhat mutually exclusive. Have you done the usual google and altavista searches on "synchronous detector"? Do a search under KE9OA. Pete is developing a sync detector for use with a MW RX they are going to market. May possibly sell the sync board separately. In talking with Pete, and having built my own sync detector- few parts and sync detectors that stay locked and retrieve hi fi audio do not go together. Dale W4OP |
I did do a version of that quasi-sync detector, using a Philips SA637
digital FM receiver chip. I took one of the limiter outputs and fed it back into the LO input of the on-board mixer. The 455kHz I.F. signal was applied to the RF input of the on-board mixer, and the audio was taken from the I.F. output of this mixer. Not bad, although the demodulated audio level was fairly low (about 50mV p-p). I was actually considering using that detector, until I discovered the appnote for the Analog Devices AD607. Pete "Avery Fineman" wrote in message ... In article , "Steve Nosko" writes: What's the essence of an AM sync detector? Extract the carrier (filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? -- Steve N, K,9;d, c. i My email has no u's. Essentially, yes. There's a further step, though, and that is locking a local mixing oscillator to the carrier frequency and mixing that with the whole thing. If the local mixing oscillator is in phase with the received carrier, the mixing results in just a DC component which can be removed easily. A carrier in-phase lock allows separate detection of the sidebands...which could be used to advantage such as having binaural audio modulation with AM. That also works out well for a quasi-stereo listening with any signal that is NOT binaurally modulated. The effect of hearing through such a detector's audio cannot accurately be described in words. Nearby-signal splatter can be "heard" as left or right of the desired signal. Strange sound but does allow the mind's own spatial filtering to sort-of blot out nearby interference. That quasi-stereo circuit is a lot more complicated (it's usually a typical Costas Loop with local mixing oscillator having shifts for quadrature phasing) than the direct amplify-limit-clip-the- bejeebers out of the carrier and mix that with whole works...as was done in the Motorola MC1330P 8-pin DIP IC (now obsolete but Kits&Parts as a few left). Len Anderson retired (from regular hours) electronic engineer person |
"Pete KE9OA" ) writes:
I did do a version of that quasi-sync detector, using a Philips SA637 digital FM receiver chip. I took one of the limiter outputs and fed it back into the LO input of the on-board mixer. The 455kHz I.F. signal was applied to the RF input of the on-board mixer, and the audio was taken from the I.F. output of this mixer. Not bad, although the demodulated audio level was fairly low (about 50mV p-p). I was actually considering using that detector, until I discovered the appnote for the Analog Devices AD607. Pete Of course, what we've tended to see is an all or nothing thing when it comes to AM (with carrier) detection. A simple diode detector, or a PLL based synchronous detector (with or without phasing for sideband selection). In some ways, it's been driven by market not by curiosity. In the early seventies, those Signetic 56X series of analog PLLs came along, and simple synchronous detectors (or outright receivers) were all over the place. Most of the people applying them in hobby circles hadn't woke up one day and said "we need a better AM detector", it was because all of a sudden one could get the function on a single IC. So there was a novelty, if nothing else. Various communication type ICs came along at that point, and people were interested in "all mode" detectors from them. Since a double balanced mixer was common to most of such ICs (the MC1496, various FM detectors, the LM373, various Plessey ICs and let's not forget Ralph Burhan making a Loran C receiver out of an IC made for simple AM/FM broadcast reception), it certainly caused an interest in simple quasi-synchronous or outright synchronous detectors. But again, it often seemed to be "how can we get the most out of this IC" rather than "let's try to improve the lowly AM detector". So there have been very little instances of biased diode detectors (I think one of the Drake receivers used one, and Rohde showed a few in his Ham Radio articles a quarter century ago, and I've seen some in Wireless World in years gone by). Whether or not that is a useful path, there never was the level of interest in trying such things that there was for synchronous detectors, even before the latter became easy with ICs. And while at one point the limiter feeding the product detector was described as a "synchronous detector" and worthy of experimentation, as fancier detectors became more common, they are dismissed as merely quasi-synchronous and maybe not even worth the effort. Yet, they are a middle ground, maybe offering some increase in performance without the extra circuitry of a PLL based detector. I can point to a 1955 (I think) article in QST where someone built a fancy receiver, with two parallel IF strips. One was AM bandwidth, the other CW bandwidth. But, there was switching at the outputs of the IF strips, so the CW strip could feed the product detector at the output of the voice IF, and get some level of increased performance. Let's not forget (to the original poster) that the whole point of going beyond a diode detector is to improve operation with weak carriers compared to the sidebands, or for that matter with adjacent channel interference. The synchronous comes about because one needs the reinserted carrier right where the incoming carrier is, but except for that need, it's all about mixing the incoming signal down to audio, just as in sideband reception. With a strong signal, the diode mixer works fine for that, mixing the sidebands with the carrier. But as the carrier weakens, or an adjacent signal becomes stronger to "capture" the detector, the simple diode detector suffers. Long before before CQ ran the article about the synchronous detector in 1958 or so, most or all hams who tried for better AM reception tried other things. Like boosting the carrier of an incoming signal in reference to the sidebands, "exalted carrier". The common, or maybe only means, of doing this was by using a Q-Multiplier, which could provide a narrow peak for the carrier, but a relatively sloppy skit so it didn't attenuate the sidebands too much. Nobody talks about this anymore, even though we've seen in this thread the comment "simple and good" don't apply to synchronous detectors. But how much improvement is needed, versus how much circuitry one is willing to accept? Michael VE2BVW |
I was just looking at my 2002 handbook, and there was a circuit for a
synchronous detector, in the receiver chapter. It wasn't "simple", but it was there. It also uses NE604s (the companion chip to the '602), which might not be available any more. "Pete Beals" wrote in message ... Has anyone implemented a simple sync detector that uses as few parts as possible? Thanks Pete |
On Wed, 21 Jan 2004 22:09:37 -0800, "Tim Wescott"
wrote: I was just looking at my 2002 handbook, and there was a circuit for a synchronous detector, in the receiver chapter. It wasn't "simple", but it was there. It also uses NE604s (the companion chip to the '602), which might not be available any more. I constructed and tested that circuit with a Yaesu FRG-100. It works reasonably well for ground wave signals. However, it has problems staying locked during carrier fades. I tinkered extensively with the phase lock gain and time constants, but to little avail. The audio quality for local MW stations was amazingly good, however... Jake Brodsky, AB3A "Beware of the massive impossible!" |
I like to try the quasi sync circuit with a limiter and product detector on
AM band. Will this work with a TRF receiver? This probably won't work with weak signals but has anyone tried this? I'm also looking into a SDR. Basically the computer and soundcard can do the sync using DSP. This work be interesting for a HAM or SW receiver. Pete |
On Sat, 24 Jan 2004 21:03:03 -0000, Pete Beals
wrote: I like to try the quasi sync circuit with a limiter and product detector on AM band. Will this work with a TRF receiver? This probably won't work with weak signals but has anyone tried this? I'm also looking into a SDR. Basically the computer and soundcard can do the sync using DSP. This work be interesting for a HAM or SW receiver. Pete It was an article in Wireless World describing AM receiver with MC1330P8 - suppose it was sort of TRF, but I never had any success with it, while MC1351P worked far better -jm http://home.online.no/~la8ak/c11.htm -- Amount of SPAM is so large that MailWasher must delete 99% of the incoming mails Cannot check every email manually. Please use intelligent title for email. Mails without titles or using just "hi" are deleted |
So all I need is a limiter and a double balanced mixer.
Well I do have a SA602. How does one make the limiter from discrete transistors? I wish to avoid very old/obsolete ICs. Pete |
Pete Beals ) writes:
I like to try the quasi sync circuit with a limiter and product detector on AM band. Will this work with a TRF receiver? This probably won't work with weak signals but has anyone tried this? An obvious point about using it as a TRF is how much selectivity will you be putting at the front end? Any time you are using a mixer to convert down to audio (as with SSB or synchronous detection of some kind for AM), you can get selectivity at audio, since it's a frequency translation. But, if you've just got a limiter open to the world, at the very least it's going to limit on the strongest local signal. If you don't have enough front end selectivity, I would think you would get relatively little tuning ability. The strongest signal will "capture" the limiter, and that will be the "carrier" that beats against the incoming signal in the mixer. When people made synchronous receivers out of the old Signetics analog PLL ICs, at least the PLL had a lock range that provided "selectivity". so they could run with little or no front end selectivity. Except for mixer overload, what you got out of the mixer was limited by the audio circuitry and your hearing, since only one frequency (plus the image) could convert down to say 0 to 3KHz from the oscilaltor frequency. The same applies to direct conversion CW/SSB receivers. A quasi-synchronous receiver will work the same way, in that the output of the mixer will be within the audio range from the "carrier" out of the limiter. But if you have no selectivity on the input to the mixer, enough to separate out signals, then the strongest signal into the limiter will prevail. Much of what I've seen about "quasi-synchronous" detectors have placed them in the IF of a superheterodyne receiver, where the IF bandwidth ensures that it only reacts to the wanted signal. The only TRF that I can think of seeing was in an old Technical Topics book from the RSGB, where there was an MC1330 (which is a quasi-synchronous detector, for TV use, though I believe the datasheet simply calls it synchronous) as the detector, but there was an stage of amplification (I think an MC1350P) ahead of it, with a couple of stages of tuned circuits. With a quasi, you do indeed need some TRF before the detector. Michael VE2BVW |
A regenerative synchronous detector can be built using a MC1330. A secondary coil
is wound over the limiter coil and connected between the limiter output pin and ground through an emitter resistor. A .1 mfd capacitor is connected across the resistor. The secondary coil must be coupled and phased so that oscillation is possible. The MC1330 will lock to the incoming carrier. Coupling the secondary coil to the limiter coil is critical and requires experimentation. Jos! VE2 AUC Michael Black wrote: Pete Beals ) writes: I like to try the quasi sync circuit with a limiter and product detector on AM band. Will this work with a TRF receiver? This probably won't work with weak signals but has anyone tried this? An obvious point about using it as a TRF is how much selectivity will you be putting at the front end? Any time you are using a mixer to convert down to audio (as with SSB or synchronous detection of some kind for AM), you can get selectivity at audio, since it's a frequency translation. But, if you've just got a limiter open to the world, at the very least it's going to limit on the strongest local signal. If you don't have enough front end selectivity, I would think you would get relatively little tuning ability. The strongest signal will "capture" the limiter, and that will be the "carrier" that beats against the incoming signal in the mixer. When people made synchronous receivers out of the old Signetics analog PLL ICs, at least the PLL had a lock range that provided "selectivity". so they could run with little or no front end selectivity. Except for mixer overload, what you got out of the mixer was limited by the audio circuitry and your hearing, since only one frequency (plus the image) could convert down to say 0 to 3KHz from the oscilaltor frequency. The same applies to direct conversion CW/SSB receivers. A quasi-synchronous receiver will work the same way, in that the output of the mixer will be within the audio range from the "carrier" out of the limiter. But if you have no selectivity on the input to the mixer, enough to separate out signals, then the strongest signal into the limiter will prevail. Much of what I've seen about "quasi-synchronous" detectors have placed them in the IF of a superheterodyne receiver, where the IF bandwidth ensures that it only reacts to the wanted signal. The only TRF that I can think of seeing was in an old Technical Topics book from the RSGB, where there was an MC1330 (which is a quasi-synchronous detector, for TV use, though I believe the datasheet simply calls it synchronous) as the detector, but there was an stage of amplification (I think an MC1350P) ahead of it, with a couple of stages of tuned circuits. With a quasi, you do indeed need some TRF before the detector. Michael VE2BVW |
"Steve Nosko" wrote in message
... Steve's imbedded comments: "Avery Fineman" wrote in message ... In article , "Steve Nosko" writes: What's the essence of an AM sync detector? Extract the carrier (filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? Steve N, K,9;d, c. i My email has no u's. ...locking a local mixing oscillator to the carrier frequency and mixing that with the whole thing. Ah yes! need a reliable LO. Absolutely not. In a homodyne receiver, it's only necessary to recover the carrier by way of a limiting amplifier. ... A carrier in-phase lock allows separate detection of the sidebands...which could be used to advantage such as having binaural audio modulation with AM. Ah yes... Back to the old three methods of generating / detecting sideband signals. What's being suggested here is a synchrodyne receiver, where an oscillator is locked to the carrier of the incoming signal. This requires a Costas loop and is not at all necessary for simple AM detection. A homodyne is sufficient. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _ |/ Principal Engineer oo\ Sonoran Radio Research (__)\ _ P.O. Box 25240 \ \ .' `. Tempe, Arizona 85285-5240 \ \ / \ \ '" \ IEEE Member #40274515 . ( ) \ '-| )__| :. \ Email: | | | | \ '. http://www.home.earthlink.net/~christrask c__; c__; '-..'.__ Graphics by Loek Frederiks |
"Steve Nosko" wrote in message
... Steve's imbedded comments: "Avery Fineman" wrote in message ... In article , "Steve Nosko" writes: What's the essence of an AM sync detector? Extract the carrier (filter/clip/amplify the bajeebers out of it) then product detect the sidebands ? Steve N, K,9;d, c. i My email has no u's. ...locking a local mixing oscillator to the carrier frequency and mixing that with the whole thing. Ah yes! need a reliable LO. Absolutely not. In a homodyne receiver, it's only necessary to recover the carrier by way of a limiting amplifier. ... A carrier in-phase lock allows separate detection of the sidebands...which could be used to advantage such as having binaural audio modulation with AM. Ah yes... Back to the old three methods of generating / detecting sideband signals. What's being suggested here is a synchrodyne receiver, where an oscillator is locked to the carrier of the incoming signal. This requires a Costas loop and is not at all necessary for simple AM detection. A homodyne is sufficient. Chris ,----------------------. High Performance Mixers and / What's all this \ Amplifiers for RF Communications / extinct stuff, anyhow? / \ _______,--------------' Chris Trask / N7ZWY _ |/ Principal Engineer oo\ Sonoran Radio Research (__)\ _ P.O. Box 25240 \ \ .' `. Tempe, Arizona 85285-5240 \ \ / \ \ '" \ IEEE Member #40274515 . ( ) \ '-| )__| :. \ Email: | | | | \ '. http://www.home.earthlink.net/~christrask c__; c__; '-..'.__ Graphics by Loek Frederiks |
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