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Reciprocating vs Synchronous Detector?
"Tom Holden" ) writes:
I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Michael VE2BVW |
"Tom Holden" ) writes:
I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Michael VE2BVW |
"Michael Black" wrote in message ... "Tom Holden" ) writes: I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. I got started on this from a schematic sent to me by a Czech ham/swl who also has a DX-394. He derived his schematic from a translation of one or more of the articles. I'm not sure he understands it because he can't explain well in English and my is Czech non-existent. The design uses discrete transistors, not many parts and is cheap. I have a breadboard version working, after a fashion. It does lock when within 200 Hz or so and sounds pretty good. I was initially puzzled by an apparent null or minimum audio in the centre of lock on DSB signals. It is fundamentally a product detector with a synchronised BFO, so the difference products of the two sidebands are anti-phase. I would assume that all synchronous demods use product detectors and would behave similarly in that regard. It definitely does better than the DX-394's envelope detector on DSB with selective fading and fades out very gracefully and cleanly on weak signals, although lock may be lost before signal is completely unreadable. At the moment my LO is very unstable with temperature. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. I found most of Olberg's HR articles at the Metro Toronto Reference Library but did not look for the IEEE Comm paper by Badessa, who I think was a colleague. I don't know if synchronous detectors were in vogue in 1971 and were known as such. Did Badessa and Olberg coin the name "Reciprocating Detector" because it was truly pioneeering work uninfluenced by the name that eventually dominated or were they trying to get a patent by tinkering with the fundamentals and giving it a different name. The only obvious thing I can see that may be different is the 500 hz filter between the local oscillator and the product detector (that's the part I haven't got working yet - a straight wire is the minimum requirement). When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Hence my posting. HR accepted 4 or 5 articles on the RD or receivers using the RD by Olberg and there appears to have been considerable response. I daresay that, if this Usenet group had been around then, there would have been some hot and heavy debates about the Reciprocating Detector! Michael VE2BVW |
"Michael Black" wrote in message ... "Tom Holden" ) writes: I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. I got started on this from a schematic sent to me by a Czech ham/swl who also has a DX-394. He derived his schematic from a translation of one or more of the articles. I'm not sure he understands it because he can't explain well in English and my is Czech non-existent. The design uses discrete transistors, not many parts and is cheap. I have a breadboard version working, after a fashion. It does lock when within 200 Hz or so and sounds pretty good. I was initially puzzled by an apparent null or minimum audio in the centre of lock on DSB signals. It is fundamentally a product detector with a synchronised BFO, so the difference products of the two sidebands are anti-phase. I would assume that all synchronous demods use product detectors and would behave similarly in that regard. It definitely does better than the DX-394's envelope detector on DSB with selective fading and fades out very gracefully and cleanly on weak signals, although lock may be lost before signal is completely unreadable. At the moment my LO is very unstable with temperature. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. I found most of Olberg's HR articles at the Metro Toronto Reference Library but did not look for the IEEE Comm paper by Badessa, who I think was a colleague. I don't know if synchronous detectors were in vogue in 1971 and were known as such. Did Badessa and Olberg coin the name "Reciprocating Detector" because it was truly pioneeering work uninfluenced by the name that eventually dominated or were they trying to get a patent by tinkering with the fundamentals and giving it a different name. The only obvious thing I can see that may be different is the 500 hz filter between the local oscillator and the product detector (that's the part I haven't got working yet - a straight wire is the minimum requirement). When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Hence my posting. HR accepted 4 or 5 articles on the RD or receivers using the RD by Olberg and there appears to have been considerable response. I daresay that, if this Usenet group had been around then, there would have been some hot and heavy debates about the Reciprocating Detector! Michael VE2BVW |
I have a Reciprocating Detector that I built from a kit of parts that I purchased
from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK Michael Black wrote: "Tom Holden" ) writes: I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Michael VE2BVW |
I have a Reciprocating Detector that I built from a kit of parts that I purchased
from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK Michael Black wrote: "Tom Holden" ) writes: I've been tinkering with an add-on project for a RS DX-394 receiver based on Stirling Olberg's (W1SNN) "Reciprocating Detector" design(s) published in Ham Radio in 1972 to 1978. Has anybody had any experience with this design. Is it fundamentally any different from a synchronous detector such as the NE602 design by OH2GF in the current ARRL Handbook? Tom I've read those articles, and specifically reread them last year, and for the life of me I really not sure how it's supposed to work. The way he explains it, it sure seems like there is some specific little bit that is happening in there. If I'm remembering, he claims it works for FM too, and I don't see how it could demodulate FM if it was just a synchronous detector. He references some professional article or paper as the source of scheme, and one would hope if someone could get ahold of that, what is going on might be clearer. When I did some searches on the internet last year, I sure didn't find anything more about it. A handful of Usenet posts, none of which added to the scheme or even an understanding of it. Michael VE2BVW |
Bob, thanks forcoming back. I'm delighted to connect with someone who has a
RD. Do you not get null or minimal audio at zero beat in the centre of the passband with your authentic RD? I thought that this would be the normal response of a product detector on symmetrical sidebands - the negative frequency product would be antiphase of the positive frequency product. There is no such null on a SSB with carrier signal such as CHU. What lock range do you get? Without the 455kHz filter in the feedback loop, I get about 400Hz. With a ceramic resonator of unknown interelectrode capacitance, I have been trying different values of parallel inductors and getting lock range of 100 Hz or less. Do you find that the RD suppresses impulse noise and static crashes? 73, Tom VE3MEO "Bob G. Mahrenholz" wrote in message ... I have a Reciprocating Detector that I built from a kit of parts that I purchased from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK |
Bob, thanks forcoming back. I'm delighted to connect with someone who has a
RD. Do you not get null or minimal audio at zero beat in the centre of the passband with your authentic RD? I thought that this would be the normal response of a product detector on symmetrical sidebands - the negative frequency product would be antiphase of the positive frequency product. There is no such null on a SSB with carrier signal such as CHU. What lock range do you get? Without the 455kHz filter in the feedback loop, I get about 400Hz. With a ceramic resonator of unknown interelectrode capacitance, I have been trying different values of parallel inductors and getting lock range of 100 Hz or less. Do you find that the RD suppresses impulse noise and static crashes? 73, Tom VE3MEO "Bob G. Mahrenholz" wrote in message ... I have a Reciprocating Detector that I built from a kit of parts that I purchased from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK |
Hi Tom,
I haven't built any of the detectors but read some on them awhile ago. I believe that if you get a null that the lock up is happening at 90 degrees out of phase. That cancels the audio. I remember reading something about that in one of the articles and that there was a way to adjust it but the rest is foggy. There is an article on the Costa system in the old CQ SSB handbook. 73 Gary K4FMX On Sun, 13 Jul 2003 21:44:18 -0400, "Tom Holden" wrote: Bob, thanks forcoming back. I'm delighted to connect with someone who has a RD. Do you not get null or minimal audio at zero beat in the centre of the passband with your authentic RD? I thought that this would be the normal response of a product detector on symmetrical sidebands - the negative frequency product would be antiphase of the positive frequency product. There is no such null on a SSB with carrier signal such as CHU. What lock range do you get? Without the 455kHz filter in the feedback loop, I get about 400Hz. With a ceramic resonator of unknown interelectrode capacitance, I have been trying different values of parallel inductors and getting lock range of 100 Hz or less. Do you find that the RD suppresses impulse noise and static crashes? 73, Tom VE3MEO "Bob G. Mahrenholz" wrote in message ... I have a Reciprocating Detector that I built from a kit of parts that I purchased from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK |
Hi Tom,
I haven't built any of the detectors but read some on them awhile ago. I believe that if you get a null that the lock up is happening at 90 degrees out of phase. That cancels the audio. I remember reading something about that in one of the articles and that there was a way to adjust it but the rest is foggy. There is an article on the Costa system in the old CQ SSB handbook. 73 Gary K4FMX On Sun, 13 Jul 2003 21:44:18 -0400, "Tom Holden" wrote: Bob, thanks forcoming back. I'm delighted to connect with someone who has a RD. Do you not get null or minimal audio at zero beat in the centre of the passband with your authentic RD? I thought that this would be the normal response of a product detector on symmetrical sidebands - the negative frequency product would be antiphase of the positive frequency product. There is no such null on a SSB with carrier signal such as CHU. What lock range do you get? Without the 455kHz filter in the feedback loop, I get about 400Hz. With a ceramic resonator of unknown interelectrode capacitance, I have been trying different values of parallel inductors and getting lock range of 100 Hz or less. Do you find that the RD suppresses impulse noise and static crashes? 73, Tom VE3MEO "Bob G. Mahrenholz" wrote in message ... I have a Reciprocating Detector that I built from a kit of parts that I purchased from W1SNN back in 1972. I use it at 455kHz in an AM broadcast receiver to eliminate selective fading. The IEEE Comm paper by Badessa lists the patent on the RD that you can look up. Also if you get a null in the center of the lock range you may be locking 90 degrees out of phase with the carrier. Bob K4QQK |
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