[Ralph] is excited about impedance matching, and why not? It is important to match the source and load impedance to get the most power out of a circuit. He’s got a whole series of videos about it. The latest? Matching using a PI network and the venerable Smith Chart.

We like that he makes each video self-contained. It does mean if you watch them all, you get some review, but that’s not a bad thing, really. He also does a great job of outlining simple concepts, such as what a complex conjugate is, that you might have forgotten.

Smith charts almost seem magical, but they are really sort of an analog computer. The color of the line and even the direction of an arrow make a difference, and [Ralph] explains it all very simply.

The example circuit is simple with a 50 MHz signal and a mismatched source and load. Using the steps and watching the examples will make it straightforward, even if you’ve never used a Smith Chart before.

The red lines plot impedance, and the blue lines show conductance and succeptance. Once everything is plotted, you have to find a path between two points on the chart. That Smith was a clever guy.

We looked at part 1 of this series earlier this year, so there are five more to watch since then. If your test gear leaves off the sign of your imaginary component, the Smith Chart can work around that for you.

[Claywoven] mostly prints with ceramics, although he does produce plastic inserts for functional parts in his designs. The ceramic parts have an interesting texture, and he wondered if the same techniques could work with plastics, too. It turns out it can, as you can see in the video below.

Ceramic printing, of course, doesn’t get solid right away, so the plastic can actually take more dramatic patterns than the ceramic. The workflow starts with Blender and winds up with a standard printer.

The example prints are lamps, although you could probably do a lot with this technique. You can select where the texturing occurs, which is important in this case to allow working threads to avoid having texture.

You will need a Blender plugin to get similar results. The target printer was a Bambu, but there’s no reason this wouldn’t work with any FDM printer.

We admire this kind of artistic print. We’ve talked before about how you can use any texture to get interesting results. If you need help getting started with Blender, our tutorial is one place to start.

The Blackberry made phones with real keyboards popular, and smartphones with touch keyboards made that input method the default. However, the old flip phone crowd had just a few telephone keys to work with. If you have a key-limited project, maybe check out the libt9 library from [FoxMoss].

There were two methods for using these limited keyboards, both of which relied on the letters above a phone key’s number. For example, the number 2 should have “ABC” above it, or, sometimes, below it.

In one scheme, you’d press the two key multiple times quickly to get the letter you wanted. One press was ‘2’ while two rapid presses made up ‘A.’ If you waited too long, you were entering the next letter (so pressing two, pausing, and pressing it again would give you ’22’ instead of ‘A’).

That’s a pain, as you might imagine. The T9 system was a bit better. It “knows” about words. So if you press, for example, ‘843’ it knows you probably meant ‘the,’ a common word. That’s better than ‘884444333’ or, if the digit is last in the rotation, ‘844433.’ Of course, that assumes you are using one of the 75,000 or so words the library knows about.

If you just want to try it, there’s a website. Now imagine writing an entire text message or e-mail like that.

Of course, there’s the Blueberry, if you really want physicality. We love that old Blackberry keyboard.

We take it for granted that we almost always have cell service, no matter where you go around town. But there are places — the desert, the forest, or the ocean — where you might not have cell service. In addition, there are certain jobs where you must be able to make a call even if the cell towers are down, for example, after a hurricane. Recently, a combination of technological advancements has made it possible for your ordinary cell phone to connect to a satellite for at least some kind of service. But before that, you needed a satellite phone.

On TV and in movies, these are simple. You pull out your cell phone that has a bulkier-than-usual antenna, and you make a call. But the real-life version is quite different. While some satellite phones were connected to something like a ship, I’m going to consider a satellite phone, for the purpose of this post, to be a handheld device that can make calls.

History

Satellites have been relaying phone calls for a very long time. Early satellites carried voice transmissions in the late 1950s. But it would be 1979 before Inmarsat would provide MARISAT for phone calls from sea. It was clear that the cost of operating a truly global satellite phone system would be too high for any single country, but it would be a boon for ships at sea.

Inmarsat, started as a UN organization to create a satellite network for naval operations. It would grow to operate 15 satellites and become a private British-based company in 1998. However, by the late 1990s, there were competing companies like Thuraya, Iridium, and GlobalStar.

The first commercial satellite phone call was in 1976. The oil platform “Deep Sea Explorer” had a call with Phillips Petroleum in Oklahoma from the coast of Madagascar. Keep in mind that these early systems were not what we think of as mobile phones. They were more like portable ground stations, often with large antennas.

For example, here was part of a press release for a 1989 satellite terminal:

…small enough to fit into a standard suitcase. The TCS-9200 satellite terminal weighs 70lb and can be used to send voice, facsimile and still photographs… The TCS-9200 starts at $53,000, while Inmarsat charges are $7 to $10 per minute.

Keep in mind, too, that in addition to the briefcase, you needed an antenna. If you were lucky, your antenna folded up and, when deployed, looked a lot like an upside-down umbrella.

However, Iridium launched specifically to bring a handheld satellite phone service to the market. The first call? In late 1998, U.S. Vice President Al Gore dialed Gilbert Grosvenor, the great-grandson of Alexander Graham Bell. The phones looked like very big “brick” phones with a very large antenna that swung out.

Of course, all of this was during the Cold War, so the USSR also had its own satellite systems: Volna and Morya, in addition to military satellites.

Location, Location, Location

The earliest satellites made one orbit of the Earth each day, which means they orbit at a very specific height. Higher orbits would cause the Earth to appear to move under the satellite, while lower orbits would have the satellite racing around the Earth.

That means that, from the ground, it looks like they never move. This gives reasonable coverage as long as you can “see” the satellite in the sky. However, it means you need better transmitters, receivers, and antennas.

This is how Inmarsat and Thuraya worked. Unless there is some special arrangement, a geosynchronous satellite only covers about 40% of the Earth.

Getting a satellite into a high orbit is challenging, and there are only so many “slots” at the exact orbit required to be geosynchronous available.  That’s why other companies like Iridium and Globalstar wanted an alternative.

That alternative is to have satellites in lower orbits. It is easier to talk to them, and you can blanket the Earth. However, for full coverage of the globe, you need at least 40 or 50 satellites.

The system is also more complex. Each satellite is only overhead for a few minutes, so you have to switch between orbiting “cell towers” all the time. If there are enough satellites, it can be an advantage because you might get blocked from one satellite by, say, a mountain, and just pick up a different one instead.

Globalstar used 48 satellites, but couldn’t cover the poles. They eventually switched to a constellation of 24 satellites. Iridium, on the other hand, operates 66 satellites and claims to cover the entire globe. The satellites can beam signals to the Earth or each other.

The Problems

There are a variety of issues with most, if not all, satellite phones. First, geosynchronous satellites won’t work if you are too far North or South since the satellite will be so low, you’ll bump into things like trees and mountains. Of course, they don’t work if you are on the wrong side of the world, either, unless there is a network of them.

Getting a signal indoors is tricky. Sometimes, it is tricky outdoors, too. And this isn’t cheap. Prices vary, but soon after the release, phones started at around $1,300, and then you paid $7 a minute to talk. The geosynchronous satellites, in particular, are subject to getting blocked momentarily by just about anything. The same can happen if you have too few satellites in the sky above you.

Modern pricing is a bit harder to figure out because of all the different plans. However, expect to pay between $50 and $150 a month, plus per-minute charges ranging from $0.25 to $1.50 per minute. In general, networks with less coverage are cheaper than those that work everywhere. Text messages are extra. So, of course, is data.

If you want to see what it really looked like to use a 1990-era Iridium phone, check out [saveitforparts] video below.

If you prefer to see an older non-phone system, check him out with an even older Inmarsat station in this video:

So it is no wonder these never caught on with the mass market. We expect that if providers can link normal cell phones to a satellite network, these older systems will fall by the wayside, at least for voice communications. Or, maybe hacker use will get cheaper. We can hope, right?

To paraphrase an old joke: How do you know if someone is a Rust developer? Don’t worry, they’ll tell you. There is a move to put Rust everywhere, even in the Linux kernel. Not going fast enough for you? Then check out Asterinas — an effort to create a Linux-compatible kernel totally in Rust.

The goal is to improve memory safety and, to that end, the project describes what they call a “framekernel.” Historically kernels have been either monolithic, all in one piece, or employ a microkernel architecture where only bits and pieces load.

A framekernel is similar to a microkernel, but some services are not allowed to use “unsafe” Rust. This minimizes the amount of code that — in theory — could crash memory safety. If you want to know more, there is impressive documentation. You can find the code on GitHub.

Will it work? It is certainly possible. Is it worth it? Time will tell. Our experience is that no matter how many safeguards you put on code, there’s no cure-all that prevents bad programming. Of course, to take the contrary argument, seat belts don’t stop all traffic fatalities, but you could just choose not to have accidents. So we do have seat belts. If Rust can prevent some mistakes or malicious intent, maybe it’s worth it even if it isn’t perfect.

Want to understand Rust? Got ten minutes?

The last time we checked in with the ELIZA archeology project, they had unearthed the earliest known copy of the code for the infamous computer psychiatrist written in MAD-SLIP. After a lot of work, that version is now running again, and there were a number of interesting surprises.

While chatbots are all the modern rage, [Joseph Weizenbaum] created what could be the first one, ELIZA, in the mid-1960s. Of course, it wasn’t as capable as what we have today, but it is a good example of how simple it is to ape human behavior.

The original host was an IBM 7094, and MAD-SLIP fell out of favor. Most versions known previously were in Lisp or even Basic. But once the original code was found, it wasn’t enough to simply understand it. They wanted to run it.

Fortunately, there is an emulator for the IBM 7094. MAD-SLIP is around, too, but for whatever reason, didn’t support all the functions that [Weizenbaum] had used. The 2,600 lines of code are mostly undocumented, and the only copy was on fanfold printer paper, so the first step was getting the text in digital form.

Once it was manually transcribed, they found some functions were missing in their MAD-SLIP version. Rewriting the functions and correcting a typo made everything work.

The original version had a learning mode that did not carry over to the later clones. There’s an example of how to teach new rules in the paper. You can also see a video (below) of the original code duplicating (nearly) the original published conversations from the 1966 paper.

We have been following the team for some time and they’ve made their work available if you want to try it. We have thought a lot about Eliza since the chatbots have started taking over.

When we were kids, it was a rite of passage to read the newly arrived Edmund catalog and dream of building our own telescope. One of our friends lived near a University, and they even had a summer program that would help you measure your mirrors and ensure you had a successful build. But most of us never ground mirrors from glass blanks and did all the other arcane steps required to make a working telescope. However, [La3emedimension] wants to tempt us again with a 3D-printable telescope kit.

Before you fire up the 3D printer, be aware that PLA is not recommended, and, of course, you are going to need some extra parts. There is supposed to be a README with a bill of parts, but we didn’t see it. However, there is a support page in French and a Discord server, so we have no doubt it can be found.

It is possible to steal the optics from another telescope or, of course, buy new. You probably don’t want to grind your own mirrors, although good on you if you do! You can even buy the entire kit if you don’t want to print it and gather all the parts yourself.

The scope is made to be ultra-portable, and it looks like it would be a great travel scope. Let us know if you build one or a derivative.

This telescope looks much different than other builds we’ve seen. If you want to do it all old school, we’ve seen a great guide.

There’s a famous old story about [Charles Steinmetz] fixing a generator for [Henry Ford]. He charged a lot of money for putting a chalk X in the spot that needed repair. When [Ford] asked for an itemization, the bill read $1 for the chalk, and the balance for knowing where to draw the X. With today’s PCB layout tools, it seems easy to put components down on a board. But, as [Kasyan TV] points out in the video below, you still have to know where to put them.

The subject components are inductors, which are particularly picky about placement, especially if you have multiple inductors. After all, inductors affect one another — that’s how transformers work. So there are definite rules about good and bad ways to put a few inductors on a board.

However, in the video, air-core coils go through several orientations to see which configuration has the most and least interference. Using a ferrite core showed similar results. The final examples use toroids and shielded inductors.

One reason ferrite toroids are popular in radio designs is that coils made this way are largely self-shielding. This makes placement easier and means you don’t need metal “cans” to shield the inductors. How much do they shield? The orientation makes a little difference, but not by much. It is more important to give them a little space between the coils. Shields work, too, but note that they also change the inductance value.

While we like the idea of grabbing a breadboard and a scope to measure things, we want to point out that you can also simulate. If you didn’t understand the title, you probably don’t listen to Propellerheads.

I ran into an old episode of Hogan’s Heroes the other day that stuck me as odd. It didn’t have a laugh track. Ironically, the show was one where two pilots were shown, one with and one without a laugh track. The resulting data ensured future shows would have fake laughter. This wasn’t the pilot, though, so I think it was just an error on the part of the streaming service.

However, it was very odd. Many of the jokes didn’t come off as funny without the laugh track. Many of them came off as cruel. That got me to thinking about how they had to put laughter in these shows to begin with. I had my suspicions, but was I way off!

Well, to be honest, my suspicions were well-founded if you go back far enough. Bing Crosby was tired of running two live broadcasts, one for each coast, so he invested in tape recording, using German recorders Jack Mullin had brought back after World War II. Apparently, one week, Crosby’s guest was a comic named Bob Burns. He told some off-color stories, and the audience was howling. Of course, none of that would make it on the air in those days. But they saved the recording.

A few weeks later, either a bit of the show wasn’t as funny or the audience was in a bad mood. So they spliced in some of the laughs from the Burns performance. You could guess that would happen, and that’s the apparent birth of the laugh track. But that method didn’t last long before someone — Charley Douglass — came up with something better.

Sweetening

The problem with a studio audience is that they might not laugh at the right times. Or at all. Or they might laugh too much, too loudly, or too long. Charley Douglass developed techniques for sweetening an audio track — adding laughter, or desweetening by muting or cutting live laughter. At first, this was laborious, but Douglass had a plan.

He built a prototype machine that was a 28-inch wooden wheel with tape glued to its perimeter. The tape had laughter recordings and a mechanical detent system to control how much it played back.

Douglass decided to leave CBS, but the prototype belonged to them. However, the machine didn’t last very long without his attention. In 1953, he built his own derivative version and populated it with laughter from the Red Skelton Show, where Red did pantomime, and, thus, there was no audio but the laughter and applause.

Do You Really Need It?

There is a lot of debate regarding fake laughter. On the one hand, it does seem to help. On the other hand, shouldn’t people just — you know — laugh when something’s funny?

There was concern, for example, that the Munsters would be scary without a laugh track. Like I mentioned earlier, some of the gags on Hogan’s Heroes are fine with laughter, but seem mean-spirited without.

Consider the Big Bang theory. If you watch a clip (below) with no laugh track, you’ll notice two things. First, it does seem a bit mean (as a commenter said: “…like a bunch of people who really hate each other…” The other thing you’ll notice is that they pause for the laugh track insertion, which, when there is no laughter, comes off as really weird.

Laugh Monopoly

Laugh tracks became very common with most single-camera shows. These were hard to do in front of an audience because they weren’t filmed in sequence. Even so, some directors didn’t approve of “mechanical tricks” and refused to use fake laughter.

Even multiple-camera shows would sometimes want to augment a weak audience reaction or even just replace laughter to make editing less noticeable. Soon, producers realized that they could do away with the audience and just use canned laughter. Douglass was essentially the only game in town, at least in the United States.

The Douglass device was used on all the shows from the 1950s through the 1970s. Andy Griffith? Yep. Betwitched? Sure. The Brady Bunch? Of course. Even the Munster had Douglass or one of his family members creating their laugh tracks.

One reason he stayed a monopoly is that he was extremely secretive about how he did his work. In 1960, he formed Northridge Electronics out of a garage. When called upon, he’d wheel his invention into a studio’s editing room and add laughs for them. No one was allowed to watch.

You can see the original “laff box” in the videos below.

The device was securely locked, but inside, we now know that the machine had 32 tape loops, each with ten laugh tracks. Typewriter-like keys allowed you to select various laughs and control their duration and intensity,

In the background, there was always a titter track of people mildly laughing that could be made more or less prominent. There were also some other sound effects like clapping or people moving in seats.

Building a laugh track involved mixing samples from different tracks and modulating their amplitude. You can imagine it was like playing a musical instrument that emits laughter.

Before you tell us, yes, there seems to be some kind of modern interface board on the top in the second video. No, we don’t know what it is for, but we’re sure it isn’t part of the original machine.

The original laff box wound up appearing on Antiques Roadshow where someone had bought it at a storage locker auction.

End of an Era

Of course, all things end. As technology got better and tastes changed, some companies — notably animation companies — made their own laugh tracks. One of Douglass’ protégés started a company, Sound One, that used better technology to create laughter, including stereo recordings and cassette tapes.

Today, laugh tracks are not everywhere, but you can still find them and, of course, they are prevalent in reruns. The next time you hear one, you’ll know the history behind that giggle.

If you want to build a more modern version of the laff box, [smogdog] has just the video for you, below.

If you were alive when 2001: A Space Odyssey was in theaters, you might have thought it didn’t really go far enough. After all, in 1958, the US launched its first satellite. The first US astronaut went up in 1961. Eight years later, Armstrong put a boot on the moon’s surface. That was a lot of progress for 11 years. The movie came out in 1968, so what would happen in 33 years? Turns out, not as much as you would have guessed back then. [The History Guy] takes us through a trip of what could have been if progress had marched on after those first few moon landings. You can watch the video below.

The story picks up way before NASA. Each of the US military branches felt like it should take the lead on space technology. Sputnik changed everything and spawned both ARPA and NASA. The Air Force, though, had an entire space program in development, and many of the astronauts for that program became NASA astronauts.

The Army also had its own stymied space program. They eventually decided it would be strategic to develop an Army base on the moon for about $6 billion. The base would be a large titanium cylinder buried on the moon that would house 12 people.

The base called for forty launches in a single year before sending astronauts, and then a stunning 150 Saturn V launches to supply building materials for the base. Certainly ambitious and probably overly ambitious, in retrospect.

There were other moon base plans. Most languished with little support or interest. The death knell, though, was the 1967 Outer Space Treaty, which forbids military bases on the moon.

While we’d love to visit a moon base, we are fine with it not being militarized. We also want our jet packs.

[Doug Brown] had a problem. He uses a dummy HDMI plug to fool a computer into thinking it has a monitor for when you want to run the computer headless. The dummy plug is a cheap device that fools the computer into thinking it has a monitor and, as such, has to send the Extended Display ID (EDID) to the computer. However, that means the plug pretends to be some kind of monitor. But what if you want it to pretend to be a different monitor?

The EDID is sent via I2C and, as you might expect, you can use the bus to reprogram the EEPROM on the dummy plug. [Doug] points out that you can easily get into trouble if you do this with, for example, a real monitor or if you pick the wrong I2C bus. So be careful.

In [Doug’s] case, he wanted to drop a 4K dummy plug to 1080p, but you could probably just as easily go the other way. After all, the plug itself couldn’t care less what kind of video you send it. It drops it all anyway.

Want to know more about HDMI? We can help out with that.

We’ve all been there. [Kasyan TV] had a universal adapter for a used laptop, and though it worked for a long time, it finally failed. Can it be fixed? Of course, it can, but it is up to you if it is worth it or not. You can find [Kasyan’s] teardown and repair in the video below.

Inside the unit, there were a surprising number of components crammed into a small area. The brick also had power factor correction. The first step, of course, was to map out the actual circuit topology.

The unit contains quite a bit of heat sinking. [Kasyan] noted that the capacitors in place were possibly operated very near their operating limit. Since the power supply burned, there was an obvious place to start looking for problems.

One of the two synchronous rectifier FETs was a dead short. Everything else seemed to be good. The original FETs were not available, but better ones were put in their place. A snubber diode, though, appeared to be the root cause of the failure. Testing with a programmable load showed the repair to be a success.

Of course, you aren’t likely to have this exact failure, but the detailed analysis of what the circuit is doing might help you troubleshoot your own power supply one day.

We were surprised none of the traces burned out, but that can be fixed, too. Oddly, this cheap supply looked to be better than some of the inexpensive bench supplies we’ve seen. Go figure.

[Bhuvanmakes] says that he has the simplest open source photobioreactor. Is it? Since it is the only photobioreactor we are aware of, we’ll assume that it is. According to the post, other designs are either difficult to recreate since they require PC boards, sensors, and significant coding.

This project uses no microcontroller, so it has no coding. It also has no sensors. The device is essentially an acrylic tube with an air pump and some LEDs.

The base is 3D printed and contains very limited electronics. In addition to the normal construction, apparently, the cylinder has to be very clean before you introduce the bioreactant.

Of course, you also need something to bioreact, if that’s even a real word. The biomass of choice in this case was Scenedesmus algae. While photobioreactors are used in commercial settings where you need to grow something that requires light, like algae, this one appears to mostly be for decorative purposes. Sort of an aquarium for algae. Then again, maybe someone has some use for this. If that’s you, let us know what your plans are in the comments.

We’ve seen a lantern repurposed into a bioreactor. It doesn’t really have the photo part, but we’ve seen a homebrew bioreactor for making penicillin.

I often ask people: What’s the most important thing you need to have a successful fishing trip? I get a lot of different answers about bait, equipment, and boats. Some people tell me beer. But the best answer, in my opinion, is fish. Without fish, you are sure to come home empty-handed.

On a recent visit to Bletchley Park, I thought about this and how it relates to World War II codebreaking. All the computers and smart people in the world won’t help you decode messages if you don’t already have the messages. So while Alan Turing and the codebreakers at Bletchley are well-known, at least in our circles, fewer people know about Arkley View.

The problem was apparent to the British. The Axis powers were sending lots of radio traffic. It would take a literal army of radio operators to record it all. Colonel Adrian Simpson sent a report to the director of MI5 in 1938 explaining that the three listening stations were not enough. The proposal was to build a network of volunteers to handle radio traffic interception.

That was the start of the Radio Security Service (RSS), which started operating out of some unused cells at a prison in London. The volunteers? Experienced ham radio operators who used their own equipment, at first, with the particular goal of intercepting transmissions from enemy agents on home soil.

At the start of the war, ham operators had their transmitters impounded. However, they still had their receivers and, of course, could all read Morse code. Further, they were probably accustomed to pulling out Morse code messages under challenging radio conditions.

Over time, this volunteer army of hams would swell to about 1,500 members. The RSS also supplied some radio gear to help in the task. MI5 checked each potential member, and the local police would visit to ensure the applicant was trustworthy. Keep in mind that radio intercepts were also done by servicemen and women (especially women) although many of them were engaged in reporting on voice communication or military communications.

Early Days

The VIs (voluntary interceptors) were asked to record any station they couldn’t identify and submit a log that included the messages to the RSS.

The hams of the RSS noticed that there were German signals that used standard ham radio codes (like Q signals and the prosign 73). However, these transmissions also used five-letter code groups, a practice forbidden to hams.

Thanks to a double agent, the RSS was able to decode the messages that were between agents in Europe and their Abwehr handlers back in Germany (the Abwehr was the German Secret Service) as well as Abwehr offices in foreign cities. Later messages contained Enigma-coded groups, as well.

Between the RSS team’s growth and the fear of bombing, the prison was traded for Arkley View, a large house near Barnet, north of London. Encoded messages went to Bletchley and, from there, to others up to Churchill. Soon, the RSS had orders to concentrate on the Abwehr and their SS rivals, the Sicherheitsdienst.

Change in Management

In 1941, MI6 decided that since the RSS was dealing with foreign radio traffic, they should be in charge, and thus RSS became SCU3 (Special Communications Unit 3).

There was fear that some operators might be taken away for normal military service, so some operators were inducted into the Army — sort of. They were put in uniform as part of the Royal Corps of Signals, but not required to do very much you’d expect from an Army recruit.

Those who worked at Arkley View would process logs from VIs and other radio operators to classify them and correlate them in cases where there were multiple logs. One operator might miss a few characters that could be found in a different log, for example.

Going 24/7

It soon became clear that the RSS needed full-time monitoring, so they built a number of Y stations with two National HRO receivers from America at each listening position. There were also direction-finding stations built in various locations to attempt to identify where a remote transmitter was.

Many of the direction finding operators came from VIs. The stations typically had four antennas in a directional array. When one of the central stations (the Y stations) picked up a signal, they would call direction finding stations using dedicated phone lines and send them the signal.

The operator would hear the phone signal in one ear and the radio signal in the other. Then, they would change the antenna pattern electrically until the signal went quiet, indicating the antenna was electrically pointing away from the signals.

The DF operator would hear this signal in one earpiece. They would then tune their radio receiver to the right frequency and match the signal from the main station in one ear to the signal from their receiver in the other ear. This made sure they were measuring the correct signal among the various other noise and interference. The DF operator would then take a bearing by rotating the dial on their radiogoniometer until the signal faded out. That indicated the antenna was pointing the wrong way which means you could deduce which way it should be pointing.

The central station could plot lines from three direction finding stations and tell the source of a transmission. Sort of. It wasn’t incredibly accurate, but it did help differentiate signals from different transmitters. Later, other types of direction-finding gear saw service, but the idea was still the same.

Interesting VIs

Most of the VIs, like most hams at the time, were men. But there were a few women, including Helena Crawley. She was encouraged to marry her husband Leslie, another VI, so they could be relocated to Orkney to copy radio traffic from Norway.

In 1941, a single VI was able to record an important message of 4,429 characters. He was bedridden from a landmine injury during the Great War. He operated from bed using mirrors and special control extensions. For his work, he receive the British Empire Medal and a personal letter of gratitude from Churchill.

Results

Because of the intercepts of the German spy agency’s communications, many potential German agents were known before they arrived in the UK. Of about 120 agents arriving, almost 30 were turned into double agents. Others were arrested and, possibly, executed.

By the end of the war, the RSS had decoded around a quarter of a million intercepts. It was very smart of MI5 to realize that it could leverage a large number of trained radio operators both to cover the country with receivers and to free up military stations for other uses.

Meanwhile, on the other side of the Atlantic, the FCC had a similar plan.

The BBC did a documentary about the work the hams did during the war. You can watch it below.

Some people love tools in their browsers. Others hate them. We certainly do like to see just how far people can push the browser and version 0.6 of CHILI3D, a browser-based CAD program, certainly pushes.

If you click the link, you might want to find the top right corner to change the language (although a few messages stubbornly refuse to use English). From there, click New Document and you’ll see an impressive slate of features in the menus and toolbars.

The export button is one of those stubborn features. If you draw something and select export, you’ll see a dialog in Chinese. Translated it has the title: Select and a checkmark for “Determined” and a red X for “Cancelled.” If you select some things in the drawing and click the green checkmark, it will export a brep file. That file format is common with CAD programs, but you’ll need to convert, probably, if you want to 3D print your design.

The project’s GitHub repository shows an impressive slate of features, but also notes that things are changing as this is alpha software. The CAD kernel is a common one brought in via WebAssembly, so there shouldn’t be many simple bugs involving geometry.

We’ve seen a number of browser-based tools that do some kind of CAD. CADmium is a recent entry into the list. Or, stick with OpenSCAD. We sometimes go low-tech for schematics.

They say that if you let a million monkeys type on a million typewriters, they will eventually write the works of Shakespeare. While not quite the same thing [bbenchoff] (why does that sound familiar?), spent some computing cycles to generate random data and, via heuristics, find valid Atari 2600 “games” in the data.

As you might expect, the games aren’t going to be things you want to play all day long. In fact, they are more like demos. However, there are a number of interesting programs, considering they were just randomly generated.

Part of the reason this works is that the Atari has a fairly simple 6502-based CPU, so it is straightforward to evaluate the code, and a complete game fits in 4 K. Still, that means there are, according to [Brian], 10¹⁰¹⁵⁹ possible ROMs. Compare that to about 10⁸⁰ protons in the visible universe, and you start to see the scale of the problem.

To cut down the problem, you need some heuristics you can infer from actual games. For one thing, at least 75% of the first 1K of a ROM should be valid opcodes. It is also easy to identify code that writes to the TV and other I/O devices. Obviously, a program with no I/O isn’t going to be an interesting one.

Some of the heuristics deal with reducing the search space. For example, a valid ROM will have a reset vector in the last two bytes, so it is possible to generate random data and then apply the small number of legal reset vectors.

Why? Do you really need a reason? If you don’t have a 2600 handy, do like [Brian] and use an emulator. We wonder if the setup would ever recreate Tarzan?

It is a good bet that if most scientists and engineers were honest, they would most like to leave something behind that future generations would remember. While Marie Curie met that standard — she was the first woman to win the Nobel prize because of her work with radioactivity, and a unit of radioactivity (yes, we know — not the SI unit) is a Curie. However, Curie also left something else behind inadvertently: radioactive residue. As the BBC explains, science detectives are retracing her steps and facing some difficult decisions about what to do with contaminated historical artifacts.

Marie was born in Poland and worked in Paris. Much of the lab she shared with her husband is contaminated with radioactive material transferred by the Curies’ handling of things like radium with their bare hands.

Some of the traces have been known for years, including some on the lab notebooks the two scientists shared. However, they are still finding contamination, including at her family home, presumably brought in from the lab.

There is some debate about whether all the contamination is actually from Marie. Her daughter, Irène, also used the office. The entire story starts when Marie realized that radioactive pitchblende contained uranium and thorium, but was more radioactive than those two elements when they were extracted. The plan was to extract all the uranium and thorium from a sample, leaving this mystery element.

It was a solid plan, but working in a store room and, later, a shed with no ventilation and handling materials bare-handed wasn’t a great idea. They did isolate two elements: polonium (named after Marie’s birth country) and radium. Research eventually proved fatal as Marie succumbed to leukemia, probably due to other work she did with X-rays. She and her husband are now in Paris’ Pantheon, in lead-lined coffins, just in case.

If you want a quick video tour of the museum, [Sem Wonders] has a video you can see, below. If you didn’t know about the Curie’s scientist daughter, we can help you with that. Meanwhile, you shouldn’t be drinking radium.

Until recently, hobby-grade digital oscilloscopes were mostly, at most, 8-bit sampling. However, newer devices offer 12-bit conversion. Does it matter? Depends. [Kiss Analog] shows where a 12-bit scope may outperform an 8-bit one.

It may seem obvious, of course. When you store data in 8-bit resolution and zoom in on it, you simply have less resolution. However, seeing the difference on real data is enlightening.

To perform the test, he used three scopes to freeze on a fairly benign wave. Then he cranked up the vertical scale and zoomed in horizontally. The 8-bit scopes reveal a jagged line where the digitizer is off randomly by a bit or so. The 12-bit was able to zoom in on a smooth waveform.

Of course, if you set the scope to zoom in in real time, you don’t have that problem as much, because you divide a smaller range by 256 (the number of slices in 8 bits). However, if you have that once-in-a-blue-moon waveform captured, you might appreciate not having to try to capture it again with different settings.

A scope doesn’t have to be physically large to do a 12-bit sample. Digital sampling for scopes has come a long way.

You might wonder why you’d repair a calculator when you can pick up a new one for a buck. [Tech Tangents] though has some old Sony calculators that used Nixie tubes, including one from the 1960s. Two of his recent finds of Sony SOBAX calculators need repair, and we think you’ll agree that restoring these historical calculators is well worth the effort. Does your calculator have a carrying handle? We didn’t think so. Check out the video below to see what that looks like.

The devices don’t even use modern ICs. Inside, there are modules of discrete parts encapsulated in epoxy. There isn’t even RAM inside, but there is a delay line memory, although it is marked “unrepairable.”

There is some interesting history about this line of calculators, and the video covers that. Apparently, the whole line of early calculators grew out of an engineer’s personal project to use transistors that were scrapped because they didn’t meet the specifications for whatever application that used them.

The handle isn’t just cosmetic. You could get an external battery pack if you really wanted a very heavy — about 14 pounds (6.3 kilograms) — and large portable calculator. We are sure the $1,000 retail price tag didn’t include a battery.

These machines are beautiful, and it is fun to see the construction of these old devices. You might think our favorite calculator is based on Star Trek. As much as we do like that, we still think the HP-41C might be the best calculator ever made, even in emulation.