sdr

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Learning SDR And DSP Hack Chat

November 9, 2020 by No comments

Join us on Wednesday, November 11th at noon Pacific for Learning SDR and DSP Hack Chat with Marc Lichtman!

“Revolution” is a term thrown about with a lot less care than it probably should be, especially in fields like electronics. It’s understandable, though — the changes to society that have resulted from the “Transistor Revolution” or the “PC Revolution” or more recently, the “AI Revolution” have been transformative, often for good and sometimes for ill. The common thread, though, is that once these revolutions came about, nothing was ever the same afterward.

Such is the case with software-defined radio (SDR) and digital signal processing (DSP). These two related fields may not seem as transformative as some of the other electronic revolutions, but when you think about it, they really have transformed the world of radio communications. SDR means that complex radio transmitters and receivers, no longer have to be implemented strictly in hardware as a collection of filters, mixers, detectors, and amplifiers; instead, they can be reduced to a series of algorithms running on a computer.

Teamed with DSP, SDR has resulted in massive shifts in the RF field, with powerful, high-bandwidth radio links being built into devices almost as an afterthought. But the concepts can be difficult to wrap one’s head around, at least when digging beyond the basics and really trying to learn how SDR and DSP work. Thankfully, Dr. Marc Lichtman, an Adjunct Professor at the University of Maryland, literally wrote the book on the subject. “PySDR: A Guide to SDR and DSP using Python” is a fantastic introduction to SDR and DSP that’s geared toward those looking to learn how to put SDR and DSP to work in practical systems. Dr. Lichtman will stop by the Hack Chat to talk about his textbook, to answer your questions on how best to learn about SDR and DSP, and to discuss what the next steps are once you conquer the basics.

join-hack-chatOur Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, November 11 at 12:00 PM Pacific time. If time zones baffle you as much as us, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

[Banner image credit: Dsimic, CC BY-SA 4.0, via Wikimedia Commons]

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Easy-SDR Gets Updates

October 30, 2020 by 1 Comment

Back in 2018, we covered [Igor’s] Easy-SDR project that aimed to provide open hardware extensions for the chap RTL-SDR receivers. If you haven’t been there for a while, it’s worth a look as there have been many recent updates. According to the author’s Reddit post:

  1. Most of the devices are now prepared for installation in a metal case measuring 80 x 50 x 20 millimeters.
  2. There’s a completely redesigned LNA design. Now, Bias Tee powered amplifiers are housed in a 50 x 25 x 25mm metal case and have N-type connectors.
  3. There’s an added amplifier based on the PGA-103 microcircuit.
  4. Added is the ability to install filters in final amplifiers (a separate printed circuit board, depending on the filter used).
  5. A new device – SPDT antenna switch for receiving antennas.
  6. The upconverter has been redesigned. Added intermediate buffer stage between the crystal generator and mixer.
  7. RF lines in all devices were recalculated to correspond to the characteristic wave impedance of 50 Ohm.
  8. Reduced size of PI attenuator PCB.

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Hackaday Links: October 18, 2020

October 18, 2020 by 2 Comments

Remember subliminal advertising? The idea was that a movie theater operator would splice a single frame showing a bucket of hot buttered popcorn into a movie, which moviegoers would see and process on a subconcious level and rush to the concession stand to buy the tub o’ petrochemical-glazed starch they suddenly craved. It may or may not work on humans, but it appears to work on cars with advanced driver assistance, which can be spoofed by “phantom street signs” flashed on electronic billboards. Security researchers at Ben Gurion University stuck an image of a stop sign into a McDonald’s ad displayed on a large LCD screen by the side of the road. That was enough to convince a Tesla Model X to put on the brakes as it passed by the sign. The phantom images were on the screen anywhere from an eighth of a second to a quarter second, so these aren’t exactly subliminal messages, but it’s still an interesting attack that bears looking into. And while we’re skeptical about the whole subliminal advertising thing in the first place, for some reason we really want a bacon cheeseburger right now.

Score one for the good guys in the battle against patent trolls. Mycroft AI, makers of open-source voice assistants, proudly announced their latest victory against what they claim are patent trolls. This appears to be one of those deals where a bunch of investors get together and buy random patents, and then claim that a company that actually built something infringes on their intellectual property. Mycroft got a letter from one such entity and decided to fight it; they’ve won two battles so far against the alleged trolls and it looks pretty good going forward. They’re not pulling their punches, either, since Mycroft is planning to go after the other parties for legal expenses and punitive damages under the State of Missouri’s patent troll legislation. Here’s hoping this sends a message to IP squatters that it may not be worth the effort and that their time and money are better spent actually creating useful things.

Good news from Mars — The Mole is finally completely buried! We’ve been following the saga of the HP³, or “Heat Flow and Physical Properties Package” aboard NASA’s Mars InSight lander for quite a while. The self-drilling “Mole”, which is essentially the guts of an impact screwdriver inside a streamlined case, has been having trouble dealing with the Martian regolith, which is simultaneously too soft to offer the friction needed to keep the penetrator in its hole, but also too hard to pierce in places where there is a “duricrust” of chemically amalgamated material below the surface. It took a lot of delicate maneuvers with the lander’s robotic arm to get the Mole back on track, and it’s clearly not out of the woods yet — it needs to get down to three meters depth or so to do the full program of science it was designed for.

If watching Martian soil experiments proceed doesn’t scratch your itch for space science, why not try running your own radio astronomy experiments? Sure, you could build your own radio telescope to do that, but you don’t even have to go that far — just log into PICTOR, the free-to-use radio telescope. It’s a 3.2-m parabolic dish antenna located near Athens, Greece that’s geared toward hydrogen line measurements of the galaxy. You can set up an observation run and have the results mailed back to you for later analysis.

Here’s a fun, quick hack for anyone who hates the constant drone of white noise coming from fans. Build Comics apparently numbers themselves among that crowd, and decided to rig up a switch to turn on their fume extractor only when the soldering iron is removed from its holder. This hack was executed on a classic old Weller soldering station, but could easily be adapted to Hakko or other irons

And finally, if you’ve never listened to a Nobel laureate give a lecture, here’s your chance. Andrea Ghez, co-winner of the 2020 Nobel Prize in physics for her work on supermassive black holes, will be giving the annual Maria Goeppert Mayer lecture at the University of Chicago. She’ll be talking about exactly what she won the Nobel for: “The Monster at the Heart of Our Galaxy”, the supermassive black hole Sagittarius A*. We suspect the talk was booked before the Nobel announcement, so in normal times the room would likely be packed. But one advantage to the age of social distancing is that everything is online, so you can tune into a livestream of the lecture on October 22.

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Hackaday Links: October 11, 2020

October 11, 2020 by 3 Comments

If you’re interested in SDR and digital signal processing but don’t know where to start, you’re in luck. Ben Hillburn, president of the GNU Radio Project, recently tweeted about an online curriculum for learning SDR and DSP using Python. The course was developed by Dr. Mark Lichtman, who was a lead on GNU Radio, and from the look of it, this is the place to go to learn about putting SDRs to use doing cool things. The course is chock full of animations that make the concepts clear, and explain what all the equations mean in a way that’s sure to appeal to practical learners.

It’s not much of a secret that the Hackaday community loves clocks. We build clocks out of everything and anything, and any unique way of telling time is rightly applauded and celebrated on our pages. But does the clock motif make a good basis for a video game? Perhaps not, but that didn’t stop Clock Simulator from becoming a thing. To “play” Clock Simulator, you advance the hands of an on-screen clock by pressing a button once per second. Now, thanks to Michael Dwyer, you don’t even have to do that one simple thing. He developed a hardware cheat for Clock Simulator that takes the 1PPS output from a GPS module and wires it into a mouse. The pulse stream clicks the mouse once per second with atomic precision, rendering the player irrelevant and making the whole thing even more pointless. Or perhaps that is the point.

Maybe we were a little hard on Clock Simulator, though — we can see how it would help achieve a Zen-like state with its requirement for steady rhythm, at least when not cheating. Another source of Zen for some is watching precision machining, and more precise, the better. We ran into this mesmerizing video of a CNC micro-coil winder and found it fascinating to watch, despite the vertical format. The winder is built from a CNC lathe, to the carriage of which a wire dispenser and tensioning attachment have been added. The wire is hair-fine and passes through a ruby nozzle with a 0.6 mm bore, and LinuxCNC controls the tiny back and forth motion of the wire as it winds onto the form. We don’t know what the coil will be used for, but we respect the precision of winding something smaller than a matchhead.

Dave Jones over at EEVblog posted a teardown video this week that goes to a place few of us have ever seen: inside a processor module for an IBM System/390 server. These servers earned the name “Big Iron” for a reason, as everything about them was engineered to perform. The processor module Dave found in his mailbag was worth $250,000 in 1991, and from the look of it was worth every penny. From the 64-layer ceramic substrate supporting up to 121 individual dies to the stout oil-filled aluminum enclosure, everything about this module is impressive. We were particularly intrigued by the spring-loaded copper pistons used to transfer heat away from each die; the 2,772 pins on the other side were pretty neat too.

Here’s an interesting question: what happens if an earthquake occurs in the middle of a 3D printing run? It’s probably not something you’ve given much thought, but it’s something that regular reader Marius Taciuc experienced recently. As he relates, the magnitude 6.7 quake that struck near Kainatu in Papua New Guinea (later adjusted to a 6.3 magnitude) resulted in a solid 15 seconds of shaking at his location, where he was printing a part on his modified Mendel/Prusa i2. The shaking showed up clearly in the part as the machine started swaying with the room. It’s probably not a practical way to make a seismograph, but it’s still an interesting artifact.

The Cable Modem To SDR Transformation

October 10, 2020 by 5 Comments

What do you do with an old cable modem in a closet? If you are [stdw] you reverse engineer it and turn it into a software-defined radio. The modem in question was a Motorola MB7220. After looking at a similar project using a different modem, it seemed like it should be doable.

Cracking open the case revealed two likely UART ports, one of which was active. The output from that UART provided a lot of info. The chip was a Broadcom BCM3383 which is a MIPS processor. It had eCos as an operating system. However, the bootloader eventually disables the UART, so there wasn’t much more investigation possible via the serial terminal.

The next step was to dump the flash memory. That required a little solder surgery to prevent the board from starting while the flash chip had power. It appeared that some key credentials and configuration data were present, but they were really backups. After doing a factory reset to remove the backups, the right data was apparent.

After some lengthy exploration, the diagnostic that builds a spectrum display gave up its data. At first, the data was just a small sample of what was really required, but it did show a local FM station as a spectrum. Eventually, the data loss rate was down to about 12% when streaming which is not great, but good enough. You can hear an audio clip of the reception. Not exactly crystal-clear quality, but not bad.

Of course, no one will use this for an FM radio. But it is a fascinating view into how far you can hack into a device like this if you have some skills and patience. There must be something about quarantine that is making people hack old gear, as we just recently saw a similar Netgear hack. Even cheap games aren’t safe.

KiwiSDR Vs RaspberrySDR — A Tale Of Two SDRs

September 30, 2020 by 45 Comments

Once you move away from the usual software defined radio (SDR) dongles, you have only a few choices unless you want to drop some serious cash. One common hobby-grade SDR is the KiwiSDR. This popular unit runs Linux and can receive up to 30 MHz. The platform uses a dedicated A/D converter, an FPGA, and BeagleBone computer. Success of course breeds imitators, and especially when you have an open source design like the Kiwi, you are going to find similar devices with possibly different end goals. That’s how the RaspberrySDR came to be. This is a very similar unit to the KiwiSDR but it uses a Raspberry Pi, along with a handful of other differences. What’s different? [KA7OEI] tells us in a recent blog post.

Other than the obvious difference of the computer and all that it entails, the RaspberrySDR has a higher speed A/D (125 MHz vs 66 MHz) and 16-bits of resolution instead of the Kiwi’s 14 bits. This combines to give the Raspberry a wider receive range (up to 60 MHz) and — in theory — better performance in terms of dynamic range and distortion.

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Hackaday Links: September 20, 2020

September 20, 2020 by 12 Comments

The announcement of Autodesk’s changes to the Fusion 360 personal use license terms this week caused quite a dustup. Our article on the announcement garnered a lot of discussion and not a few heated comments. At the end of the day, though, Autodesk is going to do what it’s going to do, and the Fusion 360 user community is just going to have to figure out how to deal with the changes. One person who decided to do something other than complain is Justin Nesselrotte, who came up with a quick and easy bulk export tool for Fusion 360. This gets to the heart of the issue since the removal of export to STEP, IGES, and SAT files is perhaps the most painful change for our community. Justin’s script automatically opens every design and exports it to the file type of your choice. Since the license changes go into effect on October 1, you’d better get cracking if you want to export your designs.

Over on Twitter, Hackaday superfriend Timon gives us a valuable lesson in “you get what you pay for.” He found that a bunch of his header pin jumper cables weren’t even remotely assembled properly. The conductors of the jumper wire were only loosely inserted into the terminal’s crimp, where apparently no crimping pressure had been applied. The wires were just rattling around inside the crimp, rather than making sold contact. We’ve covered the art and science of crimping before, and it’s pretty safe to say that these jumpers are garbage. So if you’re seeing weird results with a circuit, you might want to take a good, close look at your jumpers. And as always, caveat emptor.

The GNU Radio Conference wrapped up this week, in virtual format as so many other conferences have been this year, and it generated a load of interesting talks. They’ve got each day’s proceedings over on their YouTube channel, so the videos are pretty long; luckily, each day’s stream is indexed on the playbar, so along with the full schedule you can quickly find the talks you’re interested in. One that caught our eye was a talk on the Radio Resilience Competition, a hardware challenge where participants compete head-to-head using SDRs to get signals through in an adversarial environment. It sounds like a fascinating challenge for the RF inclined. More details about registering for the competition can be had on the Radio Resilience website.

You know those recipe sites that give you a few choices on what to make for dinner based on the ingredients you have on hand? We always thought that was a clever idea, and now something like it has come to our world. It’s called DIY Hub, and it aims to guide makers toward projects they can build based on the parts they have on hand. Users create projects on the site, either hosting the project directly on the site or providing a link to projects on another site. Either way, the project’s BOM is cataloged so that users can find something to build based on parts stored in their “Garage”. Granted, most of us suffer from the exact opposite problem of not knowing what to build next, but this could be an interesting tool for stimulating the creative process, especially for teachers and parents. It’s currently in beta, and we’d love to see a few Hackaday.io projects added to the site.

And finally, we got a tip to an oldie but a goodie: How to Build a Castle. No, we don’t expect to see a rash of 13th-century castle builds gracing our pages anytime soon — although we certainly wouldn’t be opposed to the idea. Rather, this is a little something for your binge-watching pleasure. The BBC series, which was actually called Secrets of the Castle, was a five-part 2014 offering that went into great detail on the construction of Guédelon Castle, an experimental archaeology project in France that seeks to build a castle using only the materials and methods available in the 1200s. The series is hosted by historian Ruth Goodman and archaeologists Peter Ginn and Tom Pinfold, and it’s great fun for anyone interested in history and technology.