Re: [time-nuts] Magnetic Resonance Spectrometer - redux
Bob, It's always a good sign (being a time nut) to wonder if anything around you can make a frequency standard. I myself always wonder how close to UTC stop lights are synchronized in time, or what the frequency or ADEV of a car's turn signal is, or how to measure the beat note of two or more turn signals in front of me. In just one minute you face a fine example of most of the art of time frequency measurement. Anyway, here's an answer to your Magnetic Resonance question from someone I know: -- Hello Tom-- Sure enough, this can be done, but it requires the magnet, first and foremost. From a frequency-standards point of view, it's a fail, though, since the frequency you get is directly proportional to the field strength, and will therefore show all the tempco of the permanent magnet's field -- perhaps 0.1% = 1000 ppm per Kelvin. With a modern NdFeB magnet, it's even worse, perhaps 0.4%/K. The second issue is the requirement for the field to be uniform in magnitude, perhaps to 10 ppm, over the volume of the sample. That is hard to assure in a random surplus magnet, though once you *find* a signal, you can search around for a 'sweet spot' to improve it. If you look at the TeachSpin Pulsed NMR system, http://www.teachspin.com/instruments/cw_nmr/index.shtml you'll see a modern teaching model of this sort of instrument, based on a temperature-controlled NdFeB magnet and running at about 21 MHz. Naturally the circuitry is different, and in fact modern NMR units typically use pulsed excitation and Fourier-methods detection, rather than the continuous-wave methods in vogue during the vacuum-tube era. For people who want to do homebrew NMR, I myself would recommend earth's-field NMR, which was also the subject of a Sci Am 'Amateur Scientist' column -- there, you give up the concept of a frequency standard, and you use NMR to detect the small changes in the earth's magnetic field -- that is to say, your hobby becomes magnetometry instead. Most questions welcome! Best, DVB -- /tvb - Original Message - From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, July 05, 2014 8:47 PM Subject: [time-nuts] Magnetic Resonance Spectrometer - redux First, an apology. When I changed the topic on my original post, I thought that would be OK. Apparently that's still a thread-jacking. Sorry. I'm still interested in this Magnetic Resonance Spectrometer thing, though. On page 335 of the pdf linked below by Dave, there's an experiment with an MRS using water and the magnet from a magnetron available back then. Apparently the resonant frequency of hydrogen nuclei in water is 6.131325 MHz in that magnetic field. Did anyone ever pursue this with the idea of creating a frequency standard, or was the technology just too primitive at the time? Perhaps it's a repeatability problem from the magnetic flux standpoint? I can guess that temperature changes would cause enough of a flux strength change to cause a problem, but that's just a guess. Bob - AE6RV From: DaveH i...@blackmountainforge.com To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Saturday, June 28, 2014 1:09 PM Subject: Re: [time-nuts] Loran, GPS, Lightning, Timing A PDF of the 1960 book can be found here: http://www.sciencemadness.org/library/books/projects_for_the_amateur_scientist.pdf Dave ___ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Magnetic Resonance Spectrometer - redux
Thanks Brooke. I'll look into it. It would be interesting to try to develop a frequency standard from a test tube of water. Bob From: Brooke Clarke bro...@pacific.net To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, July 6, 2014 12:20 AM Subject: Re: [time-nuts] Magnetic Resonance Spectrometer - redux Hi Bob: This is very similar to a proton precession magnetometer that measures the total magnetic field, not in vector components. There's a lot of amateur designs for these that you could use as the bases for a MRS. There is an article in the same publication for a tube type frequency standard that can be used to drive a line powered wall clock. The Magnatron magnets were probably Alinco, so if you upgraded to modern magnets it might be much more stable. http://en.wikipedia.org/wiki/Proton_magnetometer http://en.wikipedia.org/wiki/NMR Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Stewart wrote: First, an apology. When I changed the topic on my original post, I thought that would be OK. Apparently that's still a thread-jacking. Sorry. I'm still interested in this Magnetic Resonance Spectrometer thing, though. On page 335 of the pdf linked below by Dave, there's an experiment with an MRS using water and the magnet from a magnetron available back then. Apparently the resonant frequency of hydrogen nuclei in water is 6.131325 MHz in that magnetic field. Did anyone ever pursue this with the idea of creating a frequency standard, or was the technology just too primitive at the time? Perhaps it's a repeatability problem from the magnetic flux standpoint? I can guess that temperature changes would cause enough of a flux strength change to cause a problem, but that's just a guess. Bob - AE6RV From: DaveH i...@blackmountainforge.com To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Saturday, June 28, 2014 1:09 PM Subject: Re: [time-nuts] Loran, GPS, Lightning, Timing A PDF of the 1960 book can be found here: http://www.sciencemadness.org/library/books/projects_for_the_amateur_scientist.pdf Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Magnetic Resonance Spectrometer - redux
On Sat, Jul 5, 2014 at 10:47 PM, Bob Stewart b...@evoria.net wrote: First, an apology. When I changed the topic on my original post, I thought that would be OK. Apparently that's still a thread-jacking. Sorry. I'm still interested in this Magnetic Resonance Spectrometer thing, though. On page 335 of the pdf linked below by Dave, there's an experiment with an MRS using water and the magnet from a magnetron available back then. Apparently the resonant frequency of hydrogen nuclei in water is 6.131325 MHz in that magnetic field. Did anyone ever pursue this with the idea of creating a frequency standard, or was the technology just too primitive at the time? Perhaps it's a repeatability problem from the magnetic flux standpoint? I can guess that temperature changes would cause enough of a flux strength change to cause a problem, but that's just a guess. The substance recommended was Ferric Chloride as I recall. The characteristic was that the peak occurred quickly even with the rapid change in the B-field. The B-field was modulated at a 60Hz rate, enough to sweep the resonance across the oscillator's frequency. When the nuclei precessed at the frequency of the oscillator, the nuclei would absorb power from the oscillator, changing the plate-current of the oscillator. It was really just a fast grid-dip oscillator. (Well, plate dip oscillator.) Pretty simple. I keep threatening to build a new one that works much better and has a wider range, just to prove that I can. :-) And I can't think of any way of tying this to time-nuttery. If there are others still interested in this topic perhaps we can just communicate off-channel. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Magnetic Resonance Spectrometer - redux
Hi Bob: This is very similar to a proton precession magnetometer that measures the total magnetic field, not in vector components. There's a lot of amateur designs for these that you could use as the bases for a MRS. There is an article in the same publication for a tube type frequency standard that can be used to drive a line powered wall clock. The Magnatron magnets were probably Alinco, so if you upgraded to modern magnets it might be much more stable. http://en.wikipedia.org/wiki/Proton_magnetometer http://en.wikipedia.org/wiki/NMR Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Stewart wrote: First, an apology. When I changed the topic on my original post, I thought that would be OK. Apparently that's still a thread-jacking. Sorry. I'm still interested in this Magnetic Resonance Spectrometer thing, though. On page 335 of the pdf linked below by Dave, there's an experiment with an MRS using water and the magnet from a magnetron available back then. Apparently the resonant frequency of hydrogen nuclei in water is 6.131325 MHz in that magnetic field. Did anyone ever pursue this with the idea of creating a frequency standard, or was the technology just too primitive at the time? Perhaps it's a repeatability problem from the magnetic flux standpoint? I can guess that temperature changes would cause enough of a flux strength change to cause a problem, but that's just a guess. Bob - AE6RV From: DaveH i...@blackmountainforge.com To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Saturday, June 28, 2014 1:09 PM Subject: Re: [time-nuts] Loran, GPS, Lightning, Timing A PDF of the 1960 book can be found here: http://www.sciencemadness.org/library/books/projects_for_the_amateur_scientist.pdf Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
