Getting Into NMR Without The Superconducting Magnet

May 26, 2023 by Dan Maloney 14 Comments

Exploring the mysteries of quantum mechanics surely seems like an endeavor that requires room-sized equipment and racks of electronics, along with large buckets of grant money, to accomplish. And while that’s generally true, there’s quite a lot that can be accomplished on a considerably more modest budget, as this as-simple-as-it-gets nuclear magnetic resonance spectroscope amply demonstrates.

First things first: Does the “magnetic resonance” part of “NMR” bear any relationship to magnetic resonance imaging? Indeed it does, as the technique of lining up nuclei in a magnetic field, perturbing them with an electromagnetic field, and receiving the resultant RF signals as the nuclei snap back to their original spin state lies at the heart of both. And while MRI scanners and the large NMR spectrometers used in analytical chemistry labs both use extremely powerful magnetic fields, [Andy Nicol] shows us that even the Earth’s magnetic field can be used for NMR.

[Andy]’s NMR setup couldn’t be simpler. It consists of a coil of enameled copper wire wound on a 40 mm PVC tube and a simple control box with nothing more than a switch and a couple of capacitors. The only fancy bit is a USB audio interface, which is used to amplify and digitize the 2-kHz-ish signal generated by hydrogen atoms when they precess in Earth’s extremely weak magnetic field. A tripod stripped of all ferrous metal parts is also handy, as this setup needs to be outdoors where interfering magnetic fields can be minimized. In use, the coil is charged with a LiPo battery for about 10 seconds before being rapidly switched to the input of the USB amp. The resulting resonance signal is visualized using the waterfall display on SDR#.

[Andy] includes a lot of helpful tips in his excellent write-up, like tuning the coil with capacitors, minimizing noise, and estimating the exact resonance frequency expected based on the strength of the local magnetic field. It’s a great project and a good explanation of how NMR works. And it’s nowhere near as loud as an MRI scanner.

Homemade Panadapter Brings Waterfall To Old Radio

February 20, 2022 by Adam Zeloof 16 Comments

Ham radio operators can be pretty selective about their gear. Some are old-school tube purists who would never think of touching a rig containing transistors, and others are perfectly happy with the small Software Defined Radio (SDR) hooked up to their PC. The vast majority, though, of us are somewhere in between — we appreciate the classic look and feel of vintage radios as well as the convenience of modern ones. Better yet, some of us even like to combine the two by adding a few modern bells and whistles to our favorite “boat anchor.”

[Scott Baker] is one such Ham. He’s only had his license for a few months now and has already jumped into some great projects, including adding a panadapter to an old Drake R-4B Receiver. What’s a panadapter, you may ask? As [Scott] explains in his excellent writeup and video, a panadapter is a circuit that grabs a wideband signal from a radio receiver that typically has a narrowband output. The idea is that rather than just listen to somebody’s 4kHz-wide transmission in the 40m band, you can listen to a huge swath of the spectrum, covering potentially hundreds of transmissions, all at the same time.

Well, you can’t actually listen to that many transmissions at once — that would be a garbed mess. What you can do with that ultrawide signal, however, is look at it. If you take an FFT of the signal to put it in the frequency domain (by using a spectrum analyzer, or in [Scott]’s case, an SDR), you can see all sorts of different signals up and down the spectrum. This makes it a heck of a lot easier to find something to listen to — rather than spinning the dial for hours, hoping to come across a transmission, you can just see where all of the interesting signals are.

This isn’t the first (or even the twentieth) time that [Scott]’s work has graced our pages, so make sure to check some of his other incredible projects in our archives!

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Spectrogram Drawing For Fun And Coding

February 26, 2021 by Jenny List 17 Comments

It probably can’t have taken long after the first spectrum waterfall display was created, before somebody had a go at creating a waveform that would create an image in the waterfall. We don’t know who that pioneer was, but it’s over 20 years since Aphex Twin famously used the technique in their music, so it’s nothing new. If you fancy a go for yourself, [Gokberk Yaltirakli] has the project for you, creating waterfall images with an SDR from image files, using a bit of Python code.

The value here isn’t necessarily in creating the waterfall of Bitcoin logos that can be seen in the video he’s put on the page, instead it’s in the simple explanation of creating I and Q values for an SDR. The code is a bit slow so writes its values to a file which is output by a HackRF, but it could just as easily be used by any other capable output device such as GNU Radio and a soundcard if you too want an Aphex Twin moment. The hardware for displaying a spectrum waterfall doesn’t even have to be very complex.

Thanks [Leo] for the tip.

Tapping Into A Ham Radio’s Potential With SDRPlay

December 10, 2017 by Dan Maloney 18 Comments

Software-defined radios are great tools for the amateur radio operator, allowing visualization of large swaths of spectrum and letting hams quickly home in on faint signals with the click of a mouse. High-end ham radios often have this function built in, but by tapping into the RF stage of a transceiver with an SDR, even budget-conscious hams can enjoy high-end features.

With both a rugged and reliable Yaesu FT-450D and the versatile SDRPlay in his shack, UK ham [Dave (G7IYK)] looked for the best way to link the two devices. Using two separate antennas was possible but inelegant, and switching the RF path between the two devices seemed clumsy. So he settled on tapping into the RF stage of the transceiver with a high-impedance low-noise amplifier (LNA) and feeding the output to the SDRPlay. The simple LNA was built on a milled PCB. A little sleuthing with the Yaesu manual — ham radio gear almost always includes schematics — led him to the right tap point in the RF path, just before the bandpass filter network. This lets the SDRPlay see the signal before the IF stage. He also identified likely points to source power for the LNA only when the radio is not transmitting. With the LNA inside the radio and the SDRPlay outside, he now has a waterfall display and thanks to Omni-Rig remote control software, he can tune the Yaesu at the click of a mouse.

If you need to learn more about SDRPlay, [Al Williams]’ guide to GNU Radio and SDRPlay is a great place to start.

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Spectrum Painting On 2.4 GHz

August 22, 2015 by Elliot Williams 15 Comments

Give a software-defined radio (SDR) platform to a few thousand geeks, and it’s pretty predictable what will happen: hackers gotta hack. We’re only surprised that it’s happening so soon. Spectrum Painter is one of the first cool hacks to come out of the rad1o badge given out at the CCCamp 2015. It makes it dead-simple to send images in Hellschreiber mode on a few different SDR hardware platforms.

What we especially like about the project is its simplicity. Don’t get us wrong, we’re tremendous fans of GNURadio and the GNURadio Companion software radio hacking environment. But if you just want to do something simple, like send a picture of a smiley-face, the all-capable GNURadio suite is overkill.

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Waterfall Swing Set

October 14, 2012 by Jeremy Cook 21 Comments

[Doped Boron] wrote in to tell us about this waterfall swing by [Dash 7]. Naturally, we had no idea what a “waterfall swing” was. Shown at the World Maker Faire in 2011, the device is a swing set capable of accommodating one or two people using it at a time. What makes it interesting, is that water comes out of the top support bar, forming a wall of water for the riders to pass through. This wall is then broken when the swing user flies through it making for a dry experience.

According to the article, 273 solenoid valves are used to control the wall of water. These solenoids are controlled by a computer with sensors that detect where the riders are in the air and what speed they are going. As with most good hacks, it may not serve a “grown-up” purpose, but a set would definitely make a trip to the park more interesting!

Be sure to check out the videos after the break. The first shows the swing in its traditional role, but the second may be even more interesting, showing full control of the swing solenoids for water writing! Continue reading “Waterfall Swing Set” →

Waterfall Signal Visualizer From Arduino And Cellphone LCD

July 11, 2011 by Mike Szczys 12 Comments

[Leigh] is a HAM operator (you may know him as wa5znu). He is familiar with a signal visualization tool called a waterfall which plots signal strength and frequency over time. He wanted to build his own waterfall and ended up with this Arduino-based version which he calls Cascata. Cascata means waterfall in Italian which meshes nicely with Arduino’s country of origin

The display he chose is a Nokia LCD shield from SparkFun. It’s easy to plug in and there were already libraries available to drive the display. The audio input just connects to a headphone plug (you can just make it out at the bottom right in the image above) using some electrical tape. A free-formed resistor divider ensures that the signal is within a measurable range. [Leigh] found that signal noise was a bit of a problem but was able to improve his results by adding a capacitor to the Arduino headers between the VREF and GND pins.

See it in action after the break.

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