Boat Anchor Twins Get A Little Digital Help Staying On Frequency

In the ham radio trade, gear such as the old Drake units [Dr. Scott M. Baker] has in his radio shack are often referred to as “boat anchors.” It refers to big, heavy radios that were perhaps a bit overengineered compared to the state of the art at the time they were designed, and it’s actually a shame that the name has taken on something of a pejorative connotation, since some of this gear is rock solid half a century or more after it was built.

But older gear is often harder to use, at least compared to the newer radios with microcontrollers and more stable oscillators inside. To make his 1970s-era Drake “Twins” setup of separate but linked receiver and transmitter a little more fun to use, [Scott] came up with this neat Raspberry Pi-based DDS-VFO project to keep his boat anchors afloat. Compared to the original mechanically tuned variable frequency oscillator in the Drake receiver, the direct-digital synthesis method promises more stability, meaning less knob-nudging to stay on frequency.

The hardware used for the DDS-VFO is actually pretty simple — just a Raspberry Pi Zero W driving an AD9850-based signal-generator module. Sending the signal to the Twins was another matter. That was done by tapping into the injection cable linking both units, which meant a few circuit complications to deal with signal attenuation. [Scott] also added amenities like a digital frequency display, optical encoder with crank-style knob to change frequency, and a host of Cherry MX keyswitches for quick access to different features.

From the look of the video below, the Twins are now rock-solid and a lot easier to use. This project is loosely based on a recent panadapter project [Scott] undertook for the receiver side of the Twins.

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S15351 tube transmitter

Retro And New Tech Combine In This Hybrid Ham Transmitter

We’ve said it before and we’ll say it again: the best part about holding an amateur radio license is that it lets you build and use your own transmitting equipment. Hams have been doing this for more than a century — indeed, it was once the only way to get on the air — using whatever technology was available. But the mix of technologies in this low-power transmitter for the 80-meter band is something you don’t see every day.

As ham [Helge Fykse (LA6NCA)] describes in the video below, the project began when he came into possession of a bonanza of vacuum tubes — 12A6 tetrodes, specifically. The new-old-stock tubes were perfect for an RF power amplifier, but that left the problem of what to use for an oscillator. [Helge] chose to meld the old with the new and used oscillator board that he designed. The board has an ATmega88 microcontroller and an Si5351 oscillator, along with a 3V3 regulator to let the module run on 12 volts. And for a nice retro touch, [Helge] put the board in a 3D printed case that looks like an old-fashioned quartz crystal.

There are some other nice design touches here too. A low-pass filter cleans up the harmonics of the oscillator’s 3.5-MHz square wave output before feeding it to the amplifier, in a nod to proper spectrum hygiene. The primary for the amp’s air-core output transformer is hand-wound, with 3D printed spacers to keep the winding neat and even. The tuning process shown below is interesting, and the transmitter was used to make a solid contact with another ham about 100 km away. And we really liked the look of [Helge]’s shack, stuffed as it is with gear both old and new.

We’ve personally tried the Si5351 for QRP transmitters before, but this blend of the old and new really makes us want to find some tubes and get to playing.

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Add Mycelium To Your Mesh Networks

In many parts of the world, days after a good rainfall, it’s fairly common to see various species of mushrooms popping up out of the ground. These mysterious organisms aren’t the whole story, though. The living being is a vast network of hidden fibers, called mycelium, spreading through the ground and into any other organic material it can colonize. Its air of mystery and its vast reach are the inspiration for entire Star Trek shows and, of course, projects like this LoRa-based mesh network called Mycelium.

Mycelium is the invention of [Catamine] and includes many novel features compared to more typical mesh networks. For one, it is intended to be used in low power applications to give users the ability to send messages over a distributed network rather than a centralized network like a cell phone service provider. For another, the messages are able to be encrypted and authenticated, which is not currently possible with other mesh networks such as APRS. The idea is that a large network of people with nothing more complicated than an ESP32, an antenna, and this software would be able to communicate securely in situations where a centralized network is not available, whether that is from something like a natural disaster or from a governmental organization disabling the Internet during a political upheval.

The mesh network is currently in active development, and while messages can not yet be sent, the network is able to recognize nodes and maintain a keybase. There are certainly plenty of instances where something like this would be useful as we’ve seen before from other (non-encrypted) LoRa-based network solutions which are built around similar principles.

Thanks to [dearuserhron] for the tip!

A Bird 43 wattmeter and its homebrew equivalent

Homebrew Wattmeter Pays Homage To Sturdy Original

If there’s one instrument that hams and other radio enthusiasts covet, it’s the venerable Bird 43 Thruline wattmeter. The useful RF tool has barely changed in the nearly 70 years since it was first introduced, and they’re built like a tank. This makes Bird meters highly desirable, and therefore quite expensive either brand new or on the swap-meet circuit.

But radio amateurs are nothing if not resourceful, and building a homebrew version of the Bird wattmeter (in Portuguese; Google translate tool at the bottom of the page) as Brazilian ham [Luciano Sturaro (PY2BBS)] did is a good way to get your hands on one. Granted, [Luciano] had a head start: a spare line set, which is the important bit from a Bird wattmeter. The machined metal part is in effect an air-insulated section of coaxial cable that the RF signal passes through on its way from transmitter to antenna. A “slug” is inserted into the cavity in the line set to sense the RF and couple it to the meter electronics; the slug can be rotated to measure RF traveling in either direction, allowing the user to determine how much RF is getting reflected by the antenna system.

[Luciano]’s version of the meter is faithful to the sturdy construction of the original, with a solid steel case that mimics its classic lines — the case even sports the same color scheme and stout leather carry handle. There are some changes to the electronics, and the meter movement itself is different from the original, but all in all, the “Buzz 50” looks fantastic. We especially love the detailed nameplate as an homage to Bird.

The thing about Bird — and Bird-like — meters is that the slugs are like potato chips; you can’t have just one. Curious as to how these slugs work? Check out this slug repair project.

[Featured image of Bird 43 Wattmeter: Martin RF Supply]

Thanks to [Niko Huenk] for the tip!

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Hackaday Links: September 12, 2021

The last thing an astronaut or cosmonaut on the International Space Stations wants to hear from one of their crewmates is, “Do you smell plastic burning?” But that’s apparently what happened this week aboard the increasingly problematic spacecraft, as the burning smell and visible smoke spread from the Russian Zvezda module to the American side of town. The reports say it occurred while charging the station’s batteries, and we all know how dicey that can get. But apparently, the situation resolved itself somehow, as normal operations continued soon after the event. Between reports of cracks, air leaks, problems with attitude control, and even accusations of sabotage, the ISS is really starting to show its age.

Speaking of burning and batteries, normally a story about burning Tesla batteries wouldn’t raise our eyebrows much. But this story out of California introduces a potential failure mode for Tesla batteries that we hadn’t considered before. It seems a semi-truck with a load of Tesla batteries lost its brakes on Interstate 80 in the Sierra Nevada mountains and ended up flipping across the highway. Video from the scene shows the cargo, which looks like replacement batteries or perhaps batteries salvaged from wrecked cars, scattered across the highway on their shipping pallets. A fire was reported, but it’s not clear whether it was one of the batteries which had gotten compromised in the crash, or if it was something other than the batteries. Still, we hadn’t considered the potential for disaster while shipping batteries like that.

Attention all GNURadio fans — GRCon21 is rapidly approaching. Unlike most of the conferences over the last year and half, GRCon21 will actually be both live and online. We always love the post-conference dump of talks, which cover such a wide range of topics and really dive deeply into so many cool areas. We’re especially looking forward to the SETI talks, and we’re pleased to see our friend Hash, who was on the Hack Chat a while back, scheduled to talk about his smart-meter hacking efforts. The conference starts on September 20 and is being held in Charlotte, North Carolina, and virtually of course. If you attend, make sure to drop tips to your favorite talks in the tips line so we can share them with everyone.

We got a tip this week on a video about how 1/4-wave tuning stubs work. It’s a simple demonstration using a length of coax, a signal generator, and an oscilloscope to show how an unterminated feedline can reflect RF back to the transmitter, and how that can be used to build super-simple notch filters and impedance transformers. We love demos that make the mysteries of RF a little simpler — W2AEW’s videos come to mind, like this one on standing waves.

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Hackaday Links: August 1, 2021

Amateur radio operators have a saying: When all else fails, there’s ham radio. And that’s true, at least to an extent — knock out the power, tear down the phone lines, and burn up all the satellites in orbit, and there will still be hams talking about politics on 40 meters. The point is, as long as the laws of physics don’t change, hams will figure out a way to send and receive messages. In honor of that fact, the police in the city of Pune in Maharashtra, India, make it a point to exchange messages with their headquarter using Morse code once a week. The idea is to maintain a backup system, in case they can’t get a message through any other way. It’s a good idea, especially since they rotate all their radio operators through the Sunday morning ritual. We can’t imagine that most emergency services dispatchers would be thrilled about learning Morse, though.

Just because you’re a billionaire with a space company doesn’t mean you’re an astronaut. At least that’s the view of the US Federal Aviation Administration, which issued guidelines pretty much while Jeff Bezos and his merry band of cohorts were floating about above the 100-km high Kármán line in a Blue Origin “New Shepard” rocket. The FAA guidelines make it clear that those making the trip need to have actually done something to qualify as an astronaut, by “demonstrated activities during flight that were essential to public safety, or contributed to human space flight safety.” That’s good news to the “Old Shepard”, who clearly was in control of “Freedom 7” during the Mercury program. But the Bezos brothers, teenager Oliver Daemen, and Wally Funk, one of the “Mercury 13” group of women who trained to be NASA astronauts but never got to fly, were really just along for the ride, as the entire flight was automated. It doesn’t take away from the fact that they’ve been to space and you haven’t, of course, but they can’t officially call themselves astronauts. This goes to show that even billionaires can just be ballast too.

Good news, everyone — if you had anything that was being transported aboard the Ever Given, your stuff is almost there. The Suez Canal-occluding container ship finally made it to its original destination in Rotterdam, approximately four months later than originally predicted.  After plugging up the vital waterway for six days last March, the ship along with her cargo and her crew were detained in Egypt’s Great Bitter Lake, perhaps the coolest sounding body of water in the world next to the Dead Sea. Legal squabbling ensued at that point, all the while rendering whatever was in the 20,000-odd containers aboard the ship pretty much pointless. We’d imagine that even with continuous power, whatever was in the refrigerated containers must be pretty nasty by now, so there’s probably a lot of logistics and clean-up left to sort out.

I have to admit that I have a weird love of explosive bolts. I don’t know what it is, but the idea of fasteners engineered to fail in a predictable way under the influence of pyrotechnic charges just tickles something in me. I mean, I even wrote a whole article on the subject once. So when I came across this video explaining how the Space Shuttles were held to the launch pad, I really had to watch it. Surprisingly, the most interesting part of this story was not the explosive aspect, but the engineering problem of supporting the massive vehicle on the launch pad. For as graceful as the Shuttles seemed once they got into orbit, they really were ungainly beasts, especially strapped to the external fuel tank and booster. The scale of the eight frangible nuts used to secure the boosters to the pad is just jaw-dropping. We also liked the idea that NASA decided to catch the debris from the explosions in a container filled with sand.

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Hackaday Links: March 14, 2021

It’ll be Pi Day when this article goes live, at least for approximately half the globe west of the prime meridian. We always enjoy Pi Day, not least for the excuse to enjoy pie and other disc-shaped foods. It’s also cool to ponder the mysteries of a transcendental number, which usually get a good treatment by the math YouTube community. This year was no disappointment in this regard, as we found two good pi-related videos, both by Matt Parker over at Standup Maths. The first one deals with raising pi to the pi to the pi to the pi and how that may or may not result in an integer that’s tens of trillions of digits long. The second and more entertaining video is a collaboration with Steve Mould which aims to estimate the value of pi by measuring the volume of a molecular monolayer of oleic acid floating on water. The process was really interesting and the results were surprisingly accurate; this might make a good exercise to do with kids to show them what pi is all about.

Remember basic physics and first being exposed to the formula for universal gravitation? We sure do, and we remember thinking that it should be possible to calculate the force between us and our classmates. It is, of course, but actually measuring the attractive force would be another thing entirely. But researchers have done just that, using objects substantially smaller than the average high school student: two 2-mm gold balls. The apparatus the Austrian researchers built used 90-milligram gold balls, one stationary and one on a suspended arm. The acceleration between the two moves the suspended ball, which pivots a mirror attached to the arm to deflect a laser beam. That they were able to tease a signal from the background noise of electrostatic, seismic, and hydrodynamic forces is quite a technical feat.

We noticed a lot of interest in the Antikythera mechanism this week, which was apparently caused by the announcement of the first-ever complete computational model of the ancient device’s inner workings. The team from University College London used all the available data gleaned from the 82 known fragments of the mechanism to produce a working model of the mechanism in software. This in turn was used to create some wonderful CGI animations of the mechanism at work — this video is well worth the half-hour it takes to watch. The UCL team says they’re now at work building a replica of the mechanism using modern techniques. One of the team says he has some doubts that ancient construction methods could have resulted in some of the finer pieces of the mechanism, like the concentric axles needed for some parts. We think our friend Clickspring might have something to say about that, as he seems to be doing pretty well building his replica using nothing but tools and methods that were available to the original maker. And by doing so, he managed to discern a previously unknown feature of the mechanism.

We got a tip recently that JOGL, or Just One Giant Lab, is offering microgrants for open-source science projects aimed at tackling the problems of COVID-19. The grants are for 4,000€ and require a minimal application and reporting process. The window for application is closing, though — March 21 is the deadline. If you’ve got an open-source COVID-19 project that could benefit from a cash infusion to bring to fruition, this might be your chance.

And finally, we stumbled across a video highlighting some of the darker aspects of amateur radio, particularly those who go through tremendous expense and effort just to be a pain in the ass. The story centers around the Mt. Diablo repeater, an amateur radio repeater located in California. Apparently someone took offense at the topics of conversation on the machine, and deployed what they called the “Annoy-o-Tron” to express their displeasure. The device consisted of a Baofeng transceiver, a cheap MP3 player loaded with obnoxious content, and a battery. Encased in epoxy resin and concrete inside a plastic ammo can, the jammer lugged the beast up a hill 20 miles (32 km) from the repeater, trained a simple Yagi antenna toward the site, and walked away. It lasted for three days and while the amateurs complained about the misuse of their repeater, they apparently didn’t do a thing about it. The jammer was retrieved six weeks after the fact and hasn’t been heard from since.