Why Your Scanner Has A Hole In It

December 19, 2020 by 51 Comments

The SDR revolution has completely changed the way radio enthusiasts pursue their hobby, but there is still a space for the more traditional scanning receiver. If you are an American, have you ever noticed that it has a gap in its coverage between 800 and 900 MHz? The curious reason for this is explored by [J. B. Crawford], and it’s a tale of dusty laws relating to a long-gone technology, remaining on the books only because their removal requires significant political effort.

What we might today refer to as “1G” phones used an entirely analogue transmission scheme, with an easily-receivable FM carrier for the voice and extremely low-bandwidth bursts of serial data only for the purposes of managing the call. Listening to these calls was an illegal activity, but for those with the appropriate scanners it became a voyeuristic hobby within a hobby. It even made the world news via the pages of the gossip sheets, when (truthfully or not) it was credited for the leak of a revealing and controversial conversation involving Diana Princess of Wales.

This caused significant worry to the cellular phone companies who understandably didn’t want their product to become associated with insecurity. Thus they successfully petitioned the US Congress to include a clause restricting the capabilities of scanning receivers into another telecoms-related Act, and here we are three decades later with analogue phones a distant memory and the law still on the books. It may be ancient and unnecessary but there is neither the will nor the resources to remove it, so it seems destined to become one of those curious legal oddities that remains on the books for centuries. Whether an RTL-SDR breaks it is something we’ll leave for the lawyers, but the detail in the write-up makes it well worth a read.

Header image: krystof.k (Twitter) & nmuseum, CC BY-SA 3.0.

Tech Hidden In Plain Sight: The Ballpoint Pen

December 17, 2020 by 125 Comments
Would you pay $180 for a new type of writing instrument? Image via The New York Times

On a crisp fall morning in late October 1945, approximately 5,000 shoppers rushed the 32nd street Gimbel’s department store in New York City like it was Black Friday at Walmart. Things got so out of hand that fifty additional NYPD officers were dispatched to the scene. Everyone was clamoring for the hottest new technology – the ballpoint pen.

This new pen cost $12.50, which is about $180 today. For many people, the improved experience that the ballpoint promised over the fountain pen was well worth the price. You might laugh, but if you’ve ever used a fountain pen, you can understand the need for something more rugged and portable.

Ballpoint pens are everywhere these days, especially cheap ones. They’re so ubiquitous that we don’t have to carry one around or really think about them at all. Unless you’re into pens, you’ve probably never marveled at the sheer abundance of long-lasting, affordable, permanent writing instruments that are around today. Before the ballpoint, pens were a messy nuisance.

A Revolutionary Pen

A ballpoint, up close and personal. Image via Wikipedia

Fountain pens use gravity and capillary action to evenly feed ink from a cartridge or reservoir down into the metal nib. The nib is split in two tines and allows ink to flow forth when pressed against paper. It’s not that fountain pens are that delicate. It’s just that they’re only about one step above dipping a nib or a feather directly into ink.

There’s no denying that fountain pens are classy, but you’re playing with fire if you put one in your pocket. They can be a bit messy on a good day, and the cheap ones are prone to leaking ink. No matter how nice of a fountain pen you have, it has to be refilled fairly frequently, either by drawing ink up from a bottle into the pen’s bladder or inserting a new cartridge. And you’re better off using it as often as possible, since a dormant fountain pen will get clogged with dried ink.

Early ballpoint pens were modeled after fountain pens, aesthetically speaking. They had metal bodies and refillable reservoirs that only needed a top-up every couple of years, compared to once a week or so for fountain pens. Instead of a nib, ballpoints have a tiny ball bearing made of steel, brass, or tungsten carbide. These pens rely on gravity to bathe the ball in ink, which allows it to glide around in the socket like a tiny roll-on deodorant.

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Tracking Satellites: The Nitty Gritty Details

December 16, 2020 by 18 Comments

If you want to listen to satellites, you have to be able to track them as they pass over the sky. When I first started tracking amateur satellites, computing the satellite’s location in the sky was a part of the challenge. Nowadays, that’s trivial. What’s left over are all the extremely important real-world details.  Let’s take a look at a typical ham satellite tracking setup and see how it all ties together.

Rotators for Steering

The popularity of robotics, 3D printing, and CNC machines has resulted in a deluge of affordable electric motors and drivers. It’s hard to imagine that an electric motor for rotating an antenna would be anything special, but in fact, antenna rotators are non-trivial engineering designs. Most of the challenges are mechanical, not electrical — the antennas that they drive can be huge, have significant wind loading and rotational inertial, and just downright weigh a lot. A rotator design has to consider bearings, weather exposure, all kinds of loads, not just rotational. And usually a brake is required to keep the antenna pointed in windy conditions.

There’s been a 70-some year history of these mechanisms from back in the 1950s when Cornell Dubilier Electronics, the company you know as a capcacitor manufacturer, began making these rotators for television antennas in the 1950s. I was a little surprised to see that the rotator systems you can buy today are not very different from the ones we used in the 1980s, other than improved electronic controls. Continue reading “Tracking Satellites: The Nitty Gritty Details” →

Homebuilt Racing Sim Does Almost Everything From Scratch

December 12, 2020 by 16 Comments

If you desire a sim gaming rig, there are off-the-shelf options up and down the market that stretch as high as your budget can afford. Some choose to eschew this route, however and build their own from scratch. Few people go quite so far as [Popicasa POPStuDio], however.

The first version of the rig is about as hacked as you can possibly get, and it’s a joy to see it built from scrap. The wheel itself and the pedals are all built out of old PVC pipe, with a bunch of old wood screwed together for the frame. A cheap USB gamepad serves to handle input to the PC for the pedals and H-shifter. The H-shifter uses simple power switches, repurposed in an ingenious way to sense gear position. The knob itself is cast out of what appears to be hot glue. Steering is done by connecting the wheel to a flexible shaft that tips a smartphone back and forth, using its internal accelerometers and gyros to sense rotation. It’s not clear how this is tied into the PC running Project CARS, but it’s impressive nonetheless.

Version 2 of the build takes things up a notch, using an Arduino Leonardo to handle steering and pedal functions as a Human Interface Device. There’s also force feedback, via a hefty motor attached to the steering shaft via a belt drive. This version implements an H-shifter as well as paddle shifters too for a more modern experience.

Both builds are unique in the modern era for eschewing CNC or 3D printed parts. It’s all done by hand, taking days of effort, and using only basic tools. It’s refreshing to see such a complex build done with nothing but simple materials and sheer commitment. We’re sure [Popicasa POPStuDio] enjoys the rig, and we can’t wait to see where it goes next. Perhaps the next iteration will even feature a motion platform, perhaps built out of old forklift parts? Only time will tell. Video after the break.

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A Thousand Feet Under The Sea

December 11, 2020 by 15 Comments

If you were to plumb the depth of the oceans, you could only get so far with a snorkel or a SCUBA tank. We don’t know the price, but if you have enough money, you might consider the Triton 3300/6 — a six-person submersible that can go down to 3,300 feet (hence the name–get it–3300/6). Billed as “diving for the entire family,” we aren’t sure we can load grandma and the kids in something like this, but that doesn’t mean we wouldn’t like to try.

The machine can carry up to 1,760 pounds and can make 3 knots which isn’t going to set any speed records. At around 24,000 pounds, the two main thrusters are lucky to make that speed. The view bubble is apparently optically perfect acrylic made by a German company and the company claims the 100-inch diameter bubble is the world’s largest spherical acrylic pressure hull.

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ESP32 Spectrum Analyzer Taps Into Both Cores

December 10, 2020 by 16 Comments

We probably don’t need to tell the average Hackaday reader that the ESP32 is a powerful and extremely flexible microcontroller. We’ve seen some incredible projects using this affordable chip over the last few years, and by the looks of it, the best is yet to come. That’s because it always takes some time before the community can really figure out how to get the most out of a piece of hardware.

Take for example the Bluetooth audio player that [squix] was recently working on. Getting the music going was no problem with the esp32-a2dp library, but when he wanted to add some visualizations the audio quality took a serious hit. Realizing that his Fast Fourier transform (FFT) code was eating up too much processor power, it seemed like a great time for him to explore using the ESP32’s second core.

[squix] had avoided poking around with the dual-core nature of the ESP32 in the past, believing that the second core was busy handling the WiFi communication. But by using the FreeRTOS queue system, he wrote some code that collects audio data with one core and runs the actual FFT magic on the other. By balancing the workload like this, he’s able to drive the array of 64 WS2812B LEDs on the front of the Icon64 seen in the video after the break.

Even if you’re not terribly interested in running your own microcontroller disco, this project may be just the example you’ve been waiting for to help get your mind wrapped around multitasking on the ESP32. If you want to master a device with this many tricks up its sleeve, you’ll need all the help you can get.

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A Xilinx Zynq Linux FPGA Board For Under $20? The Windfall Of Decommissioned Crypto Mining

December 10, 2020 by 80 Comments

One of the exciting trends in hardware availability is the inexorable move of FPGA boards and modules towards affordability. What was once an eye-watering price is now merely an expensive one, and no doubt in years to come will become a commodity. There’s still an affordability gap at the bottom of the market though, so spotting sub-$20 Xilinx Zynq boards on AliExpress that combine a Linux-capable ARM core and an FPGA on the same silicon is definitely something of great interest. A hackerspace community friend of mine ordered one, and yesterday it arrived in the usual anonymous package from China.

There’s a Catch, But It’s Only A Small One

The heftier of the two boards, in all its glory.
The heftier of the two boards, in all its glory.

There are two boards to be found for sale, one featuring the Zynq 7000 and the other the 7010, which the Xilinx product selector tells us both have the same ARM Cortex A9 cores and Artix-7 FPGA tech on board. The 7000 includes a single core with 23k logic cells, and there’s a dual-core with 28k on the 7010. It was the latter that my friend had ordered.

So there’s the good news, but there has to be a catch, right? True, but it’s not an insurmountable one. These aren’t new products, instead they’re the controller boards for an older generation of AntMiner cryptocurrency mining rigs. The components have 2017 date codes, so they’ve spent the last three years hooked up to a brace of ASIC or GPU boards in a mining data centre somewhere. The ever-changing pace of cryptocurrency tech means that they’re now redundant, and we’re the lucky beneficiaries via the surplus market.

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