Author: Al Williams

4431 Articles

VHF/UHF Antennas, The Bad, The Ugly, And The Even Worse

July 3, 2024 by 69 Comments

When you buy a cheap ham radio handy-talkie, you usually get a little “rubber ducky” antenna with it. You can also buy many replacement ones that are at least longer. But how good are they? [Learnelectronics] wanted to know, too, so he broke out his NanoVNA and found out that they were all bad, although some were worse than others. You can see the results in the — sometimes fuzzy — video below.

Of course, bad is in the eye of the beholder and you probably suspected that most of them weren’t super great, but they do seem especially bad. So much so, that, at first, he suspected he was doing something wrong. The SWR was high all across the bands the antennas targeted.

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A Brief History Of Perpetual Motion

July 1, 2024 by 65 Comments

Conservation of energy isn’t just a good idea: It is the law. In particular, it is the first law of thermodynamics. But, apparently, a lot of people don’t really get that because history is replete with inventions that purport to run forever or produce more energy than they consume. Sometimes these are hoaxes, and sometimes they are frauds. We expect sometimes they are also simple misunderstandings.

We thought about this when we ran across the viral photo of an EV with a generator connected to the back wheel. Of course, EVs and hybrids do try to reclaim power through regenerative braking, but that’s recovering a fraction of the energy already spent. You can never pull more power out than you put in, and, in fact, you’ll pull out substantially less.

Not a New Problem

If you think this is a scourge of social media and modern vehicles, you’d be wrong. Leonardo da Vinci, back in 1494, said:

Oh ye seekers after perpetual motion, how many vain chimeras have you pursued? Go and take your place with the alchemists.

There was a rumor in the 8th century that someone built a “magic wheel,” but this appears to be little more than a myth. An Indian mathematician also claimed to have a wheel that would run forever, but there’s little proof of that, either. It was probably an overbalanced wheel where the wheel spins due to weight and gravity with enough force to keep the wheel spinning.

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Almost Google Glass In 1993

June 30, 2024 by 15 Comments

You might think Google Glass was an innovative idea, but [Allison Marsh] points out that artist [Lisa Krohn] imagined the Cyberdesk in 1993. Despite having desk in the name, the imagined prototype was really a wearable computer. Of course, in 1993, the technology wasn’t there to actually build it, but it does look like [Krohn] predicted headgear that would augment your experience.

Unlike Google Glass, the Cyberdesk was worn like a necklace. There are five disk-like parts that form a four-key keyboard and something akin to a trackpad. There were two models built, but since they were nonfunctional, they could have any imagined feature you might like. For example, the system was supposed to draw power from the sun and your body, something practical devices today don’t really do, either.

She also imagined a wrist-mounted computer with satellite navigation, a phone, and more. Then again, so did [Chester Gould] when he created Dick Tracy. The post also talks about a more modern reimagining of the Cyberdesk last year.

While this wasn’t a practical device, it is a great example of how people imagine the future. Sometimes, they miss the mark, but even then, speculative art and fiction can serve as goals for scientists and engineers who build the actual devices of the future.

We usually think about machines augmenting our intelligence and senses, but maybe we should consider more physical augmentation. We do appreciate seeing designs that are both artistic and functional.

3D Printing With A Twist

June 30, 2024 by 16 Comments

When we think about sending an STL off on the Internet for processing, we usually want someone to print it for us or we want mesh repair. But [Chuck] found an interesting project on GitHub from [Andrew Sink] that will let you add a variable amount of twist to any STL and then return it to you for printing or whatever else you use STLs for. If you don’t get what we mean, check out the video below.

The site that does the work initially loads a little gnome figure if you are too lazy to upload your own model. That’s perfect, though, because the little guy is a good example of why you might want to twist a model. With just a little work, you can make the gnome look in one direction or even look behind him.

[Chuck] shows how to use the tool for artistic effect by twisting his standard cube logo. The result is something that looks like it would be difficult to create, but could hardly be easier. The tool lets you rotate the object, too, so you can get the twist effect in the right orientation for what you want to accomplish. A great little tool for making more artistic 3D prints without learning new software. If you want some fun, you can try the version that uses sound from your microphone to control the twist.

If you’d rather twist in CAD, we can help. If you really want artsy 3D printing, you probably need to learn Blender.

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Solar Energy Plant Creates Fuel

June 29, 2024 by 24 Comments

Normally, when you think of solar power, you think about photovoltaic cells or using the sun to generate steam. But engineers at Synhelion — a spin off from ETH Zurich — had a crazy idea. Could you reverse combustion and change waste products back into fuel? The answer is yes if you can use the sun to turn things up to 1,500°C.

The input is water, carbon dioxide, and methane into syngas. The pilot plant in Germany is set to begin operations using a thermal storage device to allow the plant to operate around the clock. The new plant is slated to produce several thousand liters of fuel a year. Future plants will produce more, and they are targeting a cost of $1 per liter of fuel. The pilot plant has a 20-meter-tall tower and around 1,500 square meters of mirrors, producing 600 kW of output. The hexagonal mirrors are very thin, and the plant uses drones to aim the mirrors quickly compared to other methods.

Syngas shows up a lot lately. Getting to 1,500 degrees is a big ask, although we’ve seen ETH Zurich get to 1,000 using solar.

3D Printing With Sublime Sublimation

June 28, 2024 by 10 Comments

[Teaching Tech] got an interesting e-mail from [Johan] showing pictures of 3D prints with a dye-sublimated color image on the surface. Normally, we think of dye sublimation, we think of pressing color pictures onto fabric, especially T-shirts. But [Johan] uses a modified Epson inkjet printer and has amazing results, as you can see in the video below.

The printers use separate tanks for ink, which seems to be the key. If you already have an Espon “tank” printer, you are halfway there, but if you don’t have one, a cheap one will set you back less than $200 and maybe even less if you pick one up used.

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8-Bits And 1,120 Triodes

June 27, 2024 by 16 Comments

While it’s currently the start of summer in the Northern Hemisphere, it will inevitably get cold again. If you’re looking for a unique way of heating your workshop this year, you could do worse than build an 8-bit computer with a bunch of 6N3P vacuum tubes. While there are some technical details, you might find it a challenging build. But it is still an impressive sight, and it took 18 months to build a prototype and the final version. You can find the technical details if you want to try your hand. Oh, did we mention it takes about 200 amps? One of the prototype computers plays Pong on a decidedly low-tech display, which you can see below.

The architecture has 8 data bits and 12 address bits. It only provides six instructions, but that keeps the tube count manageable. Each tube has two triodes in one envelope and form a NOR gate which is sufficient to build everything else you need. In addition to tubes, there are reed relays and some NVRAM, a modern conceit.

Operating instructions are to turn it on and wait for the 560 tubes to warm up. Then, to quote the designer, “… I check the fire extinguisher is full, and run the code.” We wonder if one of the six instructions is halt and catch fire. Another quote from the builder is: “It has been a ridiculous amount of soldering and a fantastic amount of fun.” We can imagine.

If the computer seems familiar, we covered the first and second prototypes named ENA and Fred. We’ve also seen tube-base single-board computers.

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