I think you can get some results from orthogonal coils, but pulsing is literally a billion times better.
I think you can get some results from orthogonal coils, but pulsing is literally a billion times better.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I disagree, I have tested that, the 'flight recorder I threw deliberately) again the wall, nothing changed.
I have boards from the eighties:
Dead bug is in my opinion not as strong. I like these boards, you can bend those till those break, to the right size... Most stuff still has .1 inch pin spacing so that is nice. The unbroken boards fit in the standard euro card housing:
So, anyways for one off, prototypes, it works fine for me.
I lost my Giggle-Hertz fear some years ago, watch the wire-length versus wavelength...
Agreed, and it creates very important experience.
We assign part numbers to each of these "hard" prototypes and document them and keep them. That accumulates a valuable knowledge base, sort of an internal AoE.
We made a call on a big laser company and suggested a very improbable circuit. They were skeptical until I pulled one of my golden-ticket boards out of my backpack; a working example. Got the business.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
It's about once a decade here. It turns out that the six book 2019 set is actually a new, limited edition. And now it's sold out. The soft cover tome is still available. Somehow the prospect of getting the same old big soft cover format makes it easier for me to wait a decade until my next purchase (God willing). Elsewhere in the thread someone mentioned that late 70s through early 80s books contain decent construction details. My earliest copy is
1986, so a 1982 is on order to see what's missing from later editions. A _Building Scientific Apparatus_ was also mentioned elsewhere and is now on order. The last two editions of AoE are already in my library.Thank you, 73,
-- Don Kuenz KB7RPU There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on the previous night.
There are several advantages to hacking planar breadboards.
Controlled impedances
Edge-launch connectors
Low parasitics
Easy to use surface-mount parts
Good grounding and bypassing
Rugged construction
Everything is plainly visible and easy to use
You can write on the board and identify what it is and which connections are which. That will be there years later.
It photographs well, for future reference.
And you can ship it to a customer to try.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
John Larkin wrote wrote in :
That looks like a nice board. If it is OK and works, then you might as well put it in a box:
Show him some of Larkin's dremel cut boards or this link to images of Manhattan style circuits. Some well done prototypes there!
Mikek
Mine live in a couple of Rubbermaid bins under my bench. They occasionally get pulled out for reuse.
Fun. Six years or so ago I did a complete demo of a transcutaneous (noninvasive) blood glucose/alcohol sensor built out of dead bug signal processors, a grating spectrometer based on an RC airplane servo, Microbench and JB Weld optomechanics, and a LabJack. Took six weeks and cost $60k all up, including software. It also worked great, but the company blew a million bucks with a CM outfit in SoCal and went belly-up. A pity.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
"Building Scientific Apparatus" is a very useful book for anyone doing lab work. The only thing kind of like it is "Procedures in Experimental Physics"
Which is dated in many ways, but still full of good ideas.. and wonderful illustrations. (I'm going to take my copy home and put it on my bedside table.)
George H.
I found some 0.05" board like that, so you can use it with finer-pitch SMDs. Nice!
One of mine showed up on that page!
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I found the 1980, 1993, and 2003 ARRL Antenna Handbooks.
I doubt you'll find much of that in the ARRL handbook. In about 1980, I worked on a 200 watt CW VMOS power amplifier for some NMR contrivance. The major specification was very good linearity so that the IMD (intermodulation distortion) was as low as possible. Also, reasonably flat 50 ohm output impedance to make impedance matching to the NMR coil(s) as easy as possible. The amp worked just fine. However, I never became involved in the system design, and never saw the final product. Since then, I've done nothing with NMR. Presumably, there's been some technical progress in the last 39 years.
Looking at the photos that Google Images excavates from the web: the mechanical design of the probe coil or coils is rather complexicated. Fortunately, single frequency probe coil matching methods (i.e. coupling) that you're looking for is fairly well described with a simple "L" match: Just plug the probe coil into a network analyzer and do whatever it takes to make S21 look like 50 ohms over the frequency range of interest. Unfortunately, things rapidly become a mess with dual and triple resonant probe coils. From there and beyond, I'm ignorant of the technology and really don't know enough about the probe coil to offer any good links or methods.
Thanks, but I'll be fine. Such things happen every 5 to 10 years. I'm prepared with about 40 gallons of stored drinking water, which should be sufficient for a week or more. I could run my own test, but it takes 48 hrs to grow the bacteria in the same. I might as well wait for the water district to make the determination.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
There's usually a tuning network and a low-noise (sometimes cryo, a "chilly probe") preamp in a box just outside the main field. Some sort of t/r switching, too, since there's only one sample coil for transmit and receive.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
My water comes from my well right outside the back door. Except for the sulfur (treated with chlorine and filters) it's great :^) I do have a seeming endless supply.
George H.
So we've done things a few different ways. (Our latest nmr is all done by Norman, and I'm mostly clueless on the details.) Tuning near the coil is what we do now. But the first one had a coil on a fixed length of coax, (less than 1/4 wavelength) and a tuned series inductor for the transmitter tuning. (I'm not sure how the input was tuned, parallel C I assume. Norman did the hard parts here too. :^) You've got to have some Q on the input.
So my boss asked today if we could make a cheap kit/ gizmo that would let people 'see' proton nmr, pulse a coil, look at the ring down. Insert water sample into coil, see ring down change.
So (to have fun) the first question is how big is the sample/magnetic field? At ~2.5kHz you can see nmr in a beer can size of water in the Earth's field ~0.6 Gauss
In a permanent magnet ~0.5 Tesla (5 k Gauss) you can see a signal from .. well a few good sized drops of water. at ~20 MHz.
(proton gyromagnetic ratio is ~42 MHz/ T
4.2 kHz/ Gauss.)I've got some 8" Helmholtz coils that do ~100 Gauss at 3A. But lotsa turns and spendy.
Some permanent magnets and a yoke? The field homogeneity of little permanent magnetics is going to suck. Field homogeneity is either less volume or less Q, T2 broadening in the nmr lingo.
George H.
Small volume, but the two ring magnets from an oven magnetron yields a fairly uniform field.
Two disc magnets spaced a distance of half the diameter (just like a Helmholtz coil) gives the best homogeneity at the center of the gap. Assuming perfect uniformity of the magnets themselves, at a guess a pair of
3" discs would give a volume with a homogeneity of maybe 0.1 to 1 part in 1000 over 1 cubic centimeter volume at a field of maybe 0.2-0.4 T depending on the NdFeB grade. If you don't already have it grab a copy of FEMM and run some simulations. Not great compared to 1 part in 10^8 or 9 like a high resolution supercon NMR, but maybe enough to give a recognizable signal for under $500 for the magnet. It's been a couple of years since I did a fair number of sims with larger discs, playing around to see what useable volume I could get with 6" discs for a tiny FTMS so I could be off an order of magnitude here or there :-).-- Regards, Carl Ijames
You mention 'yoke', and I though of the old CRT deflection yokes. There are many kinds of those, for different defection angles, some older ones had permanent magnet focus. The field homogeneity in the deflection coils should be OK. But small space inside, enough for a glass test tube though. I have quite a bit of experience driving those, think of 10A currents, many turns. Should be available for next to nothing? The older ones with magnetic focus should have a nice field too over at least some length, Would that work?
You might consider offering a kit like Joe Geller's, which I don't believe he sells anymore:
In other words, instead of using specific magnets and shields to achieve a consistent result, set up the instrument to live with (and measure) the local field.
-- john, KE5FX
te:
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something like this?
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