Pi 5 And SDR Team Up For A Digital Scanner You Can Actually Afford

Listening to police and fire calls used to be a pretty simple proposition: buy a scanner, punch in some frequencies — or if you’re old enough, buy the right crystals — and you’re off to the races. It was a pretty cheap and easy hobby, all things considered. But progress marches on, and with it came things like trunking radio and digital modulation, requiring ever more sophisticated scanners, often commanding eye-watering prices.

Having had enough of that, [Top DNG] decided to roll his own digital trunking scanner on the cheap. The first video below is a brief intro to the receiver based on the combination of an RTL-SDR dongle and a Raspberry Pi 5. The Pi is set up in headless mode and runs sdrtrunk, which monitors the control channels and frequency channels of trunking radio systems, as well as decoding the P25 digital modulation — as long as it’s not encrypted; don’t even get us started on that pet peeve. The receiver also sports a small HDMI touchscreen display, and everything can be powered over USB, so it should be pretty portable. The best part? Everything can be had for about $250, considerably cheaper than the $600 or so needed to get into a purpose-built digital trunking scanner — we’re looking at our Bearcat BCD996P2 right now and shedding a few tears.

The second video below has complete details and a walkthrough of a build, from start to finish. [Top DNG] notes that sdrtrunk runs the Pi pretty hard, so a heat sink and fan are a must. We’d probably go with an enclosure too, just to keep the SBC safe. A better antenna is a good idea, too, although it seems like [Top DNG] is in the thick of things in Los Angeles, where LAPD radio towers abound. The setup could probably support multiple SDR dongles, opening up a host of possibilities. It might even be nice to team this up with a Boondock Echo. We’ve had deep dives into trunking before if you want more details.

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ThunderScan: The Wild 1980s Product That Turned A Printer Into A Scanner

Back in the 1980s, printers were expensive things. Scanners were rare, particularly for the home market, because home computers could barely handle basic graphics anyway. Back in these halcyon days, an obscure company called Thunderware built a device to convert the former into the latter. It was known as the Thunderscan, and was a scanning head built for the Apple ImageWriter dot matrix printer. Weird enough already, but this device hides some weird secrets in its design.

The actual scanning method was simple enough; the device mounted a carriage to the printer head of the ImageWriter. In that carriage was an optical reflective sensor which was scanned across a page horizontally while it was fed through the printer. So far, so normal.

The hilarious part is how the scanner actually delivered data to the Macintosh computer it was hooked up to. It did precisely nothing with the serial data lines at all, these were left for the computer to command the printer. Instead, the output of the analog optical sensor was fed to a voltage-to-frequency converter, which was then hooked up to the handshake/clock-in pin on the serial port.

The scanner software simply looked at the rate at which new characters were becoming available on the serial port as the handshake pin was toggled at various frequencies by the output of the optical sensor. Faster toggling of the pin indicated a darker section of the image, slower corresponded to lighter.

Interestingly, [Andy Hertzfeld] also has his own stories to tell on the development, for which his software contribution seems to have netted him a great sum of royalties over the years. It’s funny to think how mainstream scanners once were; and yet we barely think about them today beyond a few niche uses. Times, they change.

Thanks to [J. Peterson] for the tip!

LiPo Replacement Keeps Portable Scanner In The Action

If there’s anything people hate more than being locked into a printer manufacturer’s replacement cartridges, it’s proprietary batteries. Cordless power tools are the obvious example in this space, but there are other devices that insist on crappy battery packs that are expensive to replace when they eventually die.

One such device is the Uniden Bearcat BC296D portable scanner that [Robert Guildig] found for a song at a thrift store, which he recently gave a custom LiPo battery upgrade. It came equipped with a nickel-cadmium battery pack, which even under the best of circumstances has a very limited battery life. Using regular AA batteries wasn’t an option, but luckily the space vacated by the OEM battery pack left a lot of room for mods. Those include a small module with BMS functions and a DC-DC converter, a 2,400 mAh 4.2 V LiPo pillow pack, and a new barrel connector for charging. With the BMS set for six volts and connected right to the old battery pack socket, the scanner can now run for seven hours on a one-hour charge. As a bonus, the LiPo pack should last a few times longer than the NiCd packs, and be pretty cheap to replace when it finally goes too. There’s a video after the hop with all the details.

If you’re looking at a similar battery replacement project, you might want to check out [Arya]’s guide to everything you need to know about lithium-ion circuitry.

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Hands On With Boondock Echo

Perhaps no words fill me with more dread than, “I hear there’s something going around.” In my experience, you hear this when some nasty bug has worked its way into the community and people start getting whatever it is. I’m always on my guard when I hear about something like this, especially when it’s something really unpleasant like norovirus. Forewarned is forearmed, after all.

Since I work from home and rarely get out, one of the principal ways I keep apprised of what’s going on with public health in my community is by listening to my scanner radio. I have the local fire rescue frequencies programmed in, and if “there’s something going around,” I usually find out about it there first; after a half-dozen or so calls for people complaining of nausea and vomiting, you get the idea it’s best to hunker down for a while.

I manage to stay reasonably well-informed in this way, but it’s not like I can listen to my scanner every minute of the day. That’s why I was really excited when my friend Mark Hughes started a project he called Boondock Echo, which aims to change the two-way radio communications user experience by enabling internet-backed recording and playback. It sounded like the perfect system for me — something that would let my scanner work for me, instead of the other way around. And so when Mark asked me to participate in the beta test, I jumped at the chance.

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Using Industrial CT To Examine A $129 USB Cable

What in the world could possibly justify charging $129 for a USB cable? And is such a cable any better than a $10 Amazon Basics cable?

To answer that question, [Jon Bruner] fired up an industrial CT scanner to look inside various cables (Nitter), with interesting results. It perhaps comes as little surprise that the premium cable is an Apple Thunderbolt 4 Pro USB-C cable, which sports 40 Gb/s transfer rates and can deliver 100 Watts of power to a device. And it turns out there’s a lot going on with this cable from an engineering and industrial design perspective. The connector shell has a very compact and extremely complex PCB assembly inside it, with a ton of SMD components and at least one BGA chip. The PCB itself is a marvel, with nine layers, a maze of blind and buried vias, and wiggle traces to balance propagation delays. The cable itself contains 20 wires, ten of which are shielded coax, and everything is firmly anchored to a stainless steel shell inside the plastic connector body.

By way of comparison, [Jon] also looked under the hood at more affordable alternatives. None were close to the same level of engineering as the Apple cable, ranging as they did from a tenth to a mere 1/32nd of the price. While none of the cables contained such a complex PCB, the Amazon Basics cable seemed the best of the bunch, with twelve wires, decent shielding, and a sturdy crimped strain relief. The other cables — well, when you’re buying a $3 cable, you get what you pay for. But does that make the Apple cable worth the expense? That’s for the buyer to decide, but at least now we know there’s something in there aside from Apple’s marketing hype.

We’ve seen these industrial CT scanners used by none other than [Ken Shirriff] and [Curious Marc] to reverse engineer Apollo-era artifacts. If you want a closer look at the instrument itself, check out the video below

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A 489 Megapixel Camera For Not A Lot

The megapixel wars of a decade ago saw cameras aggressively marketed on the resolution of their sensors, but as we progressed into the tens of megapixels it became obvious even to consumers that perhaps there might be a little more to the quality of a digital camera than just its resolution. Still, it’s a frontier that still has a way to go, even if [Yunus Zenichowski]’s 489 megapixel prototype is a bit of an outlier. As some of you may have guessed it’s a scanner camera, in which the sensor is a linear CCD that is mechanically traversed over the focal plane to capture the image line by line.

In the 3D printed shell are the guts of a cheap second-hand Canon scanner, and the lens comes from a projector. Both these components make it not only one of the highest resolution cameras we’ve ever brought you, but also by no means the most expensive. It’s definitely a work in progress and the results of a sensor designed for the controlled environment of a document scanner being used with real-world light leave something to be desired, but even with the slight imperfections of the projector lens it’s still a camera capable of some fascinating high-resolution photography. The files are all available, should you be interested, and you can see it in action in the video below the break.

It’s by no means the first scanner camera we’ve brought you, though some of the earlier projects now have dead links. It is however easily the one with the highest resolution.

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Hackaday Links: April 2, 2023

It may be hard to believe, but it’s time for the Hackaday Prize again! The 2023 Hackaday Prize was announced last weekend at Hackaday Berlin, and entries are already pouring in. The first-round challenge is all about “Re-engineering Education,” which means you’ve got to come up with a project idea that helps push back the veil of ignorance somehow. Perhaps you’ve got a novel teaching tool in mind, or a way to help students learn remotely. Or maybe your project is aimed at getting students involved and engaged. Whatever it is — and whatever the subject matter; it doesn’t just have to be hacking-adjacent — get an entry together, build a team, and get to work. The first round closes on April 25, so get to it!

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