There was movement in the “AM Radio in Every Vehicle Act” last week, with the bill advancing out of the US House of Representatives Energy and Commerce Committee and heading to a full floor vote. For those not playing along at home, auto manufacturers have been making moves toward deleting AM radios from cars because they’re too sensitive to all the RF interference generated by modern vehicles. The trouble with that is that the government has spent a lot of effort on making AM broadcasters the centerpiece of a robust and survivable emergency communications system that reaches 90% of the US population.

The bill would require cars and trucks manufactured or sold in the US to be equipped to receive AM broadcasts without further fees or subscriptions, and seems to enjoy bipartisan support in both the House and the Senate. Critics of the bill will likely point out that while the AM broadcast system is a fantastic resource for emergency communications, if nobody is listening to it when an event happens, what’s the point? That’s fair, but short-sighted; emergency communications isn’t just about warning people that something is going to happen, but coordinating the response after the fact. We imagine Hurricane Helene’s path of devastation from Florida to Pennsylvania this week and the subsequent emergency response might bring that fact into focus a bit.

The US Geological Survey and NASA bid goodbye to Landsat 7 this week, 25 years into its five-year mission to watch the planet. Launched in 1999, the satellite’s imaging instruments were witness to many Earth changes, both natural and man-made. Its before-and-after images, like this look at New Orleans around the time of Hurricane Katrina, are especially striking. Despite suffering instrumentation problems within a few years of launch that degraded image quality on some of its sensors, Landsat 7 sent a wealth of geophysical data down to Earth, enough that it has over 210,000 citations in the scientific literature. The aging satellite was moved to a lower orbit in 2021 to make way for its newer cousins, Landsat 8 and 9, which put its polar sun-synchronous orbit out of sync with mission requirements. Despite this, it kept on grabbing images right up until May 28, 2024, when it grabbed a picture of Las Vegas that shows the dramatic increase in the size of the metro area over the last 25 years, along with the stunning decrease of Lake Mead.

How much do you enjoy captchas? If you’re anything like us, you’ve learned to loathe their intentionally fuzzy photos where you have to find traffic lights, stairs, motorcycles, or cars to prove you’re human. Well, surprise — just because you can (eventually) solve a captcha doesn’t make you a human. It turns out that AI can do it too. A security research group at ETH Zurich managed to modify YOLO to solve Google’s reCAPTCHAv2, saying it wasn’t even particularly hard to get it to pass the test 100% of the time within two tries. Think about that the next time you’re wondering if that tiny sliver of the rider’s helmet that intrudes just a tiny bit into one frame counts as a square containing a motorcycle.

We’re not much into cryptocurrency around here, but we do love vaults and over-the-top physical security, and that makes this article on a Swiss Bitcoin vault worth looking at. If you’re perplexed with the need for a physical vault to keep your virtual currency safe, we get it. But with people investing huge amounts of effort in excavating landfills for accidentally disposed hard drives containing Bitcoin wallets worth millions, it starts to make sense. The vault in this story is impressively well-protected, living deep within the granite of a Swiss mountain and protected from every conceivable threat. Ah, but it’s the inconceivable threats that get you, isn’t it? And when you put a lot of valuable things together in one place, well — let’s just say we’re eagerly awaiting the “based on a true story” heist film.

And finally, YouTube seems to be the go-to resource for how-to videos, and we’ve all likely gotten quick tutorials on everything from fixing a toilet to writing a will. So why not a tutorial on changing a fuel filter on an Airbus A320? Sure, you might not need to do one, and we’re pretty sure you’ll be arrested for even trying without the proper certifications, but it’s cool to see it down. All things considered, it doesn’t look all that hard, what with all the ease-of-maintenance features built into the Pratt and Whitney PW1100G engine. As we’ve spent many hours on a creeper in the driveway doing repairs that would better be done on the lift we can’t afford, we found the fact that the mechanic has to lie on his back on the tarmac to service a multimillion-dollar aircraft pleasingly ironic.

Old radios often had selenium rectifiers to convert AC to DC. The problem is that the old units, dating back to 1933, are prone to failure and to release dangerous chemicals like hydrogen selenide. [M Caldeira] has a new board made to fit a particular rectifier and also allows a varying voltage drop. The circuit consists of a few diodes, a MOSFET, and a pot for adjusting the voltage drop. An IRF840 MOSFET provides the adjustment.

Did it work? It did. The good news is that if it fails — which shouldn’t happen very often — it won’t release stinky and noxious fumes

We wondered if he should 3D print a fake case to make it look more the part. If you haven’t seen a real selenium rectifier, they were made of stacks of metal plates coated with bismuth or nickel. Then, a film of doped selenium was annealed to the surface to form cadmium selenide. Each plate could handle about 20 V and the more plates you used, the more reverse voltage the device could withstand.

Selenium was also found in old photocells. If you fancy replacing other parts of an old radio, you might consider a faux magic eye or even one of the main tubes.

For as useful as computers are in the modern ham shack, they also tend to be a strong source of unwanted radio frequency interference. Common wisdom says applying a few ferrite beads to things like Ethernet cables will help, but does that really work?

It surely appears to, for the most part at least, according to experiments done by [Ham Radio DX]. With a particular interest in lowering the noise floor for operations in the 2-meter band, his test setup consisted of a NanoVNA and a simple chunk of wire standing in for the twisted-pair conductors inside an Ethernet cable. The NanoVNA was set to sweep across the entire HF band and up into the VHF; various styles of ferrite were then added to the conductor and the frequency response observed. Simply clamping a single ferrite on the wire helped a little, with marginal improvement seen by adding one or two more ferrites. A much more dramatic improvement was seen by looping the conductor back through the ferrite for an additional turn, with diminishing returns at higher frequencies as more turns were added. The best performance seemed to come from two ferrites with two turns each, which gave 17 dB of suppression across the tested bandwidth.

The question then becomes: How do the ferrites affect Ethernet performance? [Ham Radio DX] tested that too, and it looks like good news there. Using a 30-meter-long Cat 5 cable and testing file transfer speed with iPerf, he found no measurable effect on throughput no matter what ferrites he added to the cable. In fact, some ferrites actually seemed to boost the file transfer speed slightly.

Ferrite beads for RFI suppression are nothing new, of course, but it’s nice to see a real-world test that tells you both how and where to apply them. The fact that you won’t be borking your connection is nice to know, too. Then again, maybe it’s not your Ethernet that’s causing the problem, in which case maybe you’ll need a little help from a thunderstorm to track down the issue.

For many of us of a particular vintage, the internet blossomed in the ’90s with the invention of the Web and just a few years of development. Back then, we had the convenience of expression on the WWW and the backup of mature services such as IRC for all that other stuff we used to get up to. Some of us still hang out there. Then something happened. Something terrible. Big-commerce took over, and it ballooned into this enormously complex mess with people tracking you every few seconds and constantly trying to bombard you with marketing messages. Enough now. Many people have had enough and have come together to create the Tildeverse, a minimalist community-driven internet experience.

Tilde, literally ‘ ~ ‘, is your home on the internet. You can work on your ideas on a shared server or run your own. Tilde emphasises the retro aesthetic by being minimal and text-orientated. Those unfamiliar with a command line may start getting uncomfortable, but don’t worry—help is at hand. The number of activities is too many to list, but there are a few projects, such as a collaborative Sci-Fi story, a radio station, and even a private VoIP server. Gamers are catered for as long as you like Minecraft, but we think that’s how it should go.

The Tildeverse also supports Gopher and the new Gemini protocol,  giving some people a few more options with which to tinker. The usual method to gain access is to first sign up on a server, then SSH into it; you’re then taken to your little piece of the internet, ready to start your minimalist journey into the Tildeverse.

A couple of videos after the break go into much more detail about the whys and hows of the Tildeverse and are worth a chunk of your time.

We’ve talked about the ‘small web’ before. Here’s our guide to Gemini.

Thanks to [Andrew] for the tip!

[Mikrowave1] wanted to build an authentic 1930s-style ham radio station that was portable. He’s already done a regenerative receiver, but now he’s starting on a tube transmitter that runs on batteries. He’s settled on a popular design for the time, a Jones push-pull transmitter. Despite the tubes, it will only put out a few watts, which is probably good for the batteries which, at the time, wouldn’t have been like modern batteries. You can see the kickoff video below.

According to the video, these kinds of radios were popular with expeditions to exotic parts of the world. He takes a nostalgic look back at some of the radios and antennas used in some of those expeditions.

The Jones oscillator originates with [Frank Jones, W6AJF] and was quite popular in the day, as he was well-known in ham radio circles then. Normally, these took a dual triode and a crystal along with some passive components. In this case, though, the transmitter will use two type 30 tubes. If you missed the series on the receiver, that’ll give you something to watch while you wait for the next installment on the transmitter.

We are excited to see — and maybe hear — this station on the air. Of course, you can build simple gear today, too. You can only wonder what [Frank Jones] would think of modern software-defined radios.

[MIKROWAVE1] claims he’s not a radio repair guy, but he agreed to look at a malfunctioning Hallicrafters S-120 shortwave receiver. He lets us watch as he tries to get it in shape in the video below. You’ll see that one of his subscribers had done a great job restoring the radio, but it just didn’t work well.

Everything looked great including the restored parts, so it was a mystery why things wouldn’t work. However, every voltage measured was about 20V too low. Turns out that the series fuse resistor had changed value and was dropping too much voltage.

That was an easy fix and got three of the radio’s four bands working. The fourth band had some problems. Fixing some grounding helped, but the converter tube was weak and a new replacement made it work much better.

There were some other minor issues, but in the end, the radio was back to its original glory. We have to warn you that restoring old radios can be addictive. The good news is, thanks to the Internet, you don’t have to figure it all out yourself or find a local expert who will take an apprentice. Hallicrafters was a huge name in the radio business after World War II, and, for that matter, during the war, too.

When you think of Sony, you probably think of a technology company that’s been around forever. However, as [Asianometry] points out, it really formed in the tough years after World War II. The two people behind the company’s formation were an interesting pair. One of them was a visionary engineer and one was a consummate businessman.

While it is hard to imagine today, securing a license to produce transistors was difficult in the early days. What’s worse is, even with the license, it was not feasible to use the crude devices in a radio.

The devices were poor by today’s standards, and while transistors would work at audio frequencies for hearing aids, getting them to work at AM radio frequencies was a challenge. The Sony founders had to decide whether to use alloy transistors or grown crystal transistors.

Western Electric did not want to share its crystal-growing technology, so in 1954, the team created an alloy transistor. However, it failed to work well at radio frequencies, so they shifted to growing crystals, which seemed more amenable to scaling. One of the team tried using phosphorous and indium doping and created a transistor that could work at higher frequencies. But there was a problem.

Despite the transistor’s superior performance, they couldn’t make another one. Common wisdom at the time was that phosphorus doping was a dead end, but it had worked once. It just took time to find the right way to do it. By 1955, they produced usable transistors, even though the yield was at around 5%.

Texas Instruments beat them to market with a transistor radio, the Regency TR-1, in 1954, but in 1955, they produced the TR-55. Of the five transistors inside, some were alloyed transistors, and some were grown crystals. The factory had to hand-select crystal transistors to make each unit work. The radios were on sale for about 19,000 yen (the TR-1 cost about 50 bucks; recall that in 1954, that was nearly $600 in today’s money). Adjusting for inflation, in today’s money, a Japanese teenager would shell out about $850 for the TR-55.

The TR-55 wasn’t the first Sony radio to have transistors. The TR-52 was a prototype, but it had case problems and never made it into the hands of the public. The radio didn’t make it to the United States until 1957. By then, Texas Instruments, Raytheon, and GE all had radios available, too.

It is a fascinating look into the history of an iconic electronics brand and a window into another world that, honestly, wasn’t that long ago. We couldn’t help but note similarities with Apple, who also had a businessman and engineer combination. Sony would go on to innovate in a number of areas, including optical data storage.

With as cheap and versatile as RTL-SDR devices are, it’s a good idea to have a couple of them on hand for some rainy day hacking. In fact, depending on what signals you’re trying to sniff out of the air, you may need multiple interfaces anyway. Once you’ve amassed this arsenal of software defined radios, you may find yourself needing a way to transport and deploy them. Luckily, [Jay Doscher] has you covered.

His latest creation, the SDR SOLO, is a modular system for mounting RTL-SDRs. Each dongle is encased in its own 3D printed frame, which not only protects it, but makes it easy to attach to the base unit. To keep the notoriously toasty radios cool, each frame has been designed to maximize airflow. You can even mount a pair of 80 mm fans to the bottom of the stack to really get the air moving. The current design is based around the RTL-SDR Blog V4, but could easily be adapted to your dongle of choice.

In addition to the row of SDR dongles, the rig also includes a powered USB hub. Each radio connects to the hub via a short USB cable, which means that you’ll only need a single USB cable running back to your computer. There’s also various mounts and adapters for attaching antennas to the system. Stick it all on the end of a tripod, and you’ve got a mobile radio monitoring system that’ll be the envy of the hackerspace.

As we’ve come to expect, [Jay] put a lot of thought and effort into the CAD side of this project. Largely made of 3D printed components, his projects often feature a rugged and professional look that really stands out.

Radar made a huge impact when it was first invented, allowing objects to be detected using radio waves which would normally be difficult or impossible to observe through other means. Radio waves of all frequencies can be used for radar as well, whether that’s detecting ships beyond the horizon, tracking aircraft near an airport, penetrating the ground, or imaging objects with a high resolution. At the millimeter wavelength it’s fairly easy to detect humans with the right hardware, and using some inexpensive radar modules [Tech Dregs] shows us how to add this capability a home automation system.

Since these modules aren’t trying to image humans with fine detail or detect them at long range, the hardware can be fairly inexpensive. [Tech Dregs] is using the LD2410B modules which have not only an on-board microcontroller but also have the radio antennas used for radar built right onto the PCB. They have a simple binary output which can communicate whether or not a human is detected, but there’s also UART for communicating more details about what the module senses in the room. [Tech Dregs] is using this mode to connect the modules to Home Assistant, where they will be used to help automate his home’s lighting.

The only significant problem he had setting these modules up was getting them built into an enclosure. The short wavelengths used in this type of radar module don’t penetrate solid objects very well at all, so after trying to hide one behind an e-ink screen he eventually settled on hollowing out a space in a bezel with very thin plastic between the module and the room. If you need more out of your radar modules than object detection, though, you can always try building a pulse compression radar which can provide much more accurate ranging of objects.