Author: Dan Maloney

3372 Articles

Lowering The Boom On Yagi Element Isolation

May 10, 2020 by 19 Comments

Antenna design can be confusing, to say the least. There’s so much black magic that goes into antennas that newbies often look at designs and are left wondering exactly how the thing could ever work. Slight changes in length or the angle between two elements result in a vastly different resonant frequency or a significant change in the antenna’s impedance. It can drive one to distraction.

Particularly concerning are the frequent appearances of what seem to be dead shorts between the two conductors of a feedline, which [andrew mcneil] explored with a pair of WiFi Yagi antennas. These highly directional antennas have a driven element and a number of parasitic elements, specifically a reflector behind the driven element and one or more directors in front of it. Constructive and destructive interference based on the spacing of the elements and capacitive or inductive coupling based on their length determine the characteristics of the antenna. [Andrew]’s test antennas have their twelve directors either isolated from the boom or shorted together to the shield of the feedline. In side-by-side tests with a known signal source, both antennas performed exactly the same, meaning that if you choose to build a Yagi, you’ve got a lot of flexibility in what materials you choose and how you attach elements to the boom.

If you want to dive a little deeper into how the Yagi works, and to learn why it’s more properly known as the Yagi-Uda antenna, check out our story on their history and operational theory. And hats off to [andrew] for reminding us that antenna design is often an exercise in practicality; after all, an umbrella and some tin cans or even a rusty nail will do under the right circumstances.

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Hackaday Links: May 10, 2020

May 10, 2020 by 16 Comments

It’s a meme come true: DEF CON is canceled. Or at least canceled as the large, IRL conference that the hacker gathering has grown into. Rather than risk drawing people from all over the world and stuffing them into a Las Vegas convention hall in August, Dark Tangent has taken the prudent step of switching DEF CON 28 to a virtual meeting. If you’re interested in his reasoning behind the switch, check out his blog post on the decision. For more details on participating in DEF CON 28 in “Safe Mode”, see the FAQ.

Think that wearing a mask in public protects you from the surveillance state? Think again. Facial recognition software concern Rank One has announced new algorithms that only need to see your face from the mask up to make a match. It would seem to us that the limited number of mappable features in the periocular space would increase the error rate, and according to Rank One’s published data, that seems to be the case. But the relative error rate is still low, so expect to see this and similar periocular algorithms deployed widely. Your only defense may be to adopt the tactical shemagh as everyday wear. If only they made an N95 version.

The tech news this week was abuzz with descriptions of a new “non-fossil fuel jet engine” that could soon be powering aircraft devoid of paying passengers across our skies and perhaps directly into space using only battery power. Those reports were a bit overwrought since the experiment in question was a laboratory-scale setup using a magnetron that could have come from a smallish microwave to generate a plasma-air stream with 11 Newtons of thrust. That corresponds to an efficiency that beats that of current electric airplane engines, like those used on the Airbus E-Fan, if the extrapolation holds. So the technology is promising, but it still has a long way to go.

In what’s perhaps the longest beta in history, Inkscape 1.0 was officially released this week.

Something big — literally — is going on at Dalibor Farný’s Nixie tube factory. He dropped a video this week teasing the production of enormous Nixies for a large display installation. Each tube in the 11 by 11 tube display will be 150 mm in diameter, making them the largest Nixies ever made. Dalibor has already done much of the design work and has even started on the glasswork; the resulting tube looks a bit like the old iconoscope tubes from early TV cameras. We expect that scaling up a Nixie and producing 121 of them will present some interesting challenges, and we look forward to watching his progress.

If you’re part of a hackerspace, you should probably look at Vancouver Hackspace’s virtual tour. Not only does it show off what appears to be a great hackerspace, the video style is a great lesson in building up the excitement needed to recruit new members. There are also some great ideas in there about space layout and organization that you can leverage for your own hackerspace or even your home shop.

And finally, it’s Mother’s Day here in the US and almost 100 other countries, and circumstances may sadly keep many of us from being with Mom today. So here’s to the women who tolerated the often messy hobbies many of us pursued in our youths, who were always attentive audiences as we showed off our latest blinkenlights, and perhaps even inspired us to follow in their footsteps. Thanks, Mom!

Portable MRI Machine Comes To The Patient

May 8, 2020 by 41 Comments

To say that the process of installing a magnetic resonance imager in a hospital is a complex task is a serious understatement. Once the approval of regulators is obtained, a process that could take years, architects and engineers have to figure out where the massive machine can be installed. An MRI suite requires a sizable electrical service to be installed, reinforced floors to handle the massive weight of the magnet, and special shielding in the walls and ceiling. And once the millions have been spent and the whole thing is up and running, there are ongoing safety concerns when working around a gigantic magnet that can suck ferromagnetic objects into it at any time.

MRI studies can reveal details of diseases and injuries that no other imaging modality can match, which justifies the massive capital investments hospitals make to obtain them. But what if MRI scanners could be miniaturized? Is there something inherent in the technology that makes them so massive and so expensive that many institutions are priced out of the market? Or has technology advanced far enough that a truly portable MRI?

It turns out that yes, an inexpensive MRI scanner is not only possible, but can be made portable enough to wheel into a patient care room. It’s not without compromise, but such a device could make a huge impact on diagnostic medicine and extend MRI technologies into places far beyond the traditional hospital setting.

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Fail Of The Week: Bright Idea For LED Signs Goes Bad

May 8, 2020 by 43 Comments

Typically when we select a project for “Fail to the Week” honors, it’s because something went wrong with the technology of the project. But the tech of [Leo Fernekes]’ innovative LED sign system was never the problem; it was the realities of scaling up to production as well as the broken patent process that put a nail in this promising project’s coffin, which [Leo] sums up succinctly as “The Inventor’s Paradox” in the video below.

The idea [Leo] had a few years back was pretty smart. He noticed that there was no middle ground between cheap, pre-made LED signs and expensive programmable signboards, so he sought to fill the gap. The result was an ingenious “LED pin”, a tiny module with an RGB LED and a microcontroller along with a small number of support components. The big idea is that each pin would store its own part of a display-wide animation in flash memory. Each pin has two terminals that connect to metal cladding on either side of the board they attach to. These two conductors supply not only power but synchronization for all the pins with a low-frequency square wave. [Leo]’s method for programming the animations — using a light sensor on each pin to receive signals from a video projector — is perhaps even more ingenious than the pins themselves.

[Leo]’s idea seemed destined for greatness, but alas, the cruel realities of scaling up struck hard. Each prototype pin had a low part count, but to be manufactured economically, the entire BOM would have to be reduced to almost nothing. That means an ASIC, but the time and expense involved in tooling up for that were too much to bear. [Leo] has nothing good to say about the patent game, either, which his business partners in this venture insisted on playing. There’s plenty of detail in the video, but he sums it up with a pithy proclamation: “Patents suck.”

Watching this video, it’s hard not to feel sorry for [Leo] for all the time he spent getting the tech right only to have no feasible way to get a return on that investment. It’s a sobering tale for those of us who fancy ourselves to be inventors, and a cautionary tale about the perils of participating in a patent system that clearly operates for the benefit of the corporations rather than the solo inventor. It’s not impossible to win at this game, as our own [Bob Baddeley] shows us, but it is easy to fail.

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Turn Folds Into Flowers, But Not With Origami

May 5, 2020 by 13 Comments

It is said that you’re not a sysadmin if you haven’t warmed up a sandwich on server. OK, it’s not widely said; we made it up, and only said it once, coincidentally enough after heating up a sandwich on a server. But we stand by the central thesis: never let a good source of excess thermal energy go to waste.

[Joseph Marlin] is in the same camp, but it’s not lunch that he’s warming up. Instead, he’s using the heat generated by his Folding@Home rig to sprout seeds for beautiful tropical flowers. A native of South Africa Strelitzia reginae, better known as the striking blue and orange Bird of Paradise flower, prefers a temperature of at least 80° F (27° C) for the two months its seeds take to sprout. With all the extra CPU cycles on a spare laptop churning out warm air, [Joseph] rigged an incubator of sorts from a cardboard box. A 3D-printed scoop snaps over the fan output on the laptop and funnels warm air into the grow chamber. This keeps the interior temperature about 15 degrees above ambient, which should be good enough for the seeds to sprout. He says that elaborations for future versions could include an Arduino and a servo-controlled shutter to regulate the temperature, which seems like a good idea.

The Bird of Paradise is a spectacular flower, but if growing beautiful things isn’t your style, such a rig could easily sprout tomatoes or peppers or get onions off to a good start. No matter what you grow, you’ll need to basics of spinning up a Folding@Home rig, which is something we can help with, of course.

The Clickiest Keyboard Ever

May 5, 2020 by 62 Comments

No matter how clicky your keyboard is, nothing compares to the sensory experience of using a typewriter. The sounds that a typewriter makes, from the deep clunk of hitting the spacebar to the staccato of keys striking paper to the ratchety kerchunk of returning the carriage, are a delight compared to the sterile, soulless clicks of even the noisiest computer keyboard. Oh, and the bell — who doesn’t love the bell?

Unwilling to miss out on the feel of real typing, [Jatin Patel] whipped up this solenoid-powered typewriter simulator. The first version had the core functionality, with a line of six solenoids mounted to a strip of wood. The coils are connected to an Arduino through a relay board; a Python program running on his PC reads every keypress and tells the Arduino which solenoid to fire. Each one sounds different somehow, perhaps due to its position on the board, or maybe due to differences in mounting methods. Whatever the cause, the effect is a realistic variability in the sounds, just like a real typewriter.

Version two, shown in the video below, ups the simulation with a motor that moves the solenoid rack one step with each keypress, to simulate the moving carriage of a typewriter. The last solenoid rings a bell when it’s time to return the carriage, which is done with a combination wrench as a handle. Weird hex, but OK.

Can’t get enough typewriter action? We understand; check out this typewriter-cum-USB keyboard, the tweeting typewriter, or this manual typewriter that pulls some strings.

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The Vaccine Factory Inside You: RNA Vaccine Basics

May 4, 2020 by 19 Comments

As the world pulls back from the acute phase of the COVID-19 pandemic, it enters what will be perhaps a more challenging time: managing the long-term presence of the SARS-CoV-2 virus that causes the disease. In the roughly two-century history of modern vaccination practices, we’ve gotten pretty good at finding ways to protect ourselves from infectious diseases, and there’s little doubt that we’ll do the same for SARS-CoV-2. But developing a vaccine against any virus or bacterium takes time, and in a pandemic situation, time is exactly what’s at a premium.

In an effort to create an effective vaccine against this latest viral threat, scientists and physicians around the world have been taking a different approach to inoculation. Rather than stimulating the immune system in the usual way with a weakened sample of the virus, they’re trying to use the genetic material of the virus to stimulate an immune response. These RNA vaccines are a novel approach to a novel infection, and understanding how they work will be key to deciding whether they’ll be the right way to attack this pandemic.

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