Capstan Winch Central To This All-Band Adjustable Dipole Antenna

February 23, 2021 by 18 Comments

The perfect antenna is the holy grail of amateur radio. But antenna tuning is a game of inches, and since the optimum length of an antenna depends on the frequency it’s used on, the mere act of spinning the dial means that every antenna design is a compromise. Or perhaps not, if you build this infinitely adjustable capstan-winch dipole antenna.

Dipoles are generally built to resonate around the center frequency of one band, and with allocations ranging almost from “DC to daylight”, hams often end up with a forest of dipoles. [AD0MZ]’s adjustable dipole solves that problem, making the antenna usable from the 80-meter band down to 10 meters. To accomplish this feat it uses something familiar to any sailor: a capstan winch.

The feedpoint of the antenna contains a pair of 3D-printed drums, each wound with a loop of tinned 18-gauge antenna wire attached to some Dacron cord. These make up the adjustable-length elements of the antenna, which are strung through pulleys suspended in trees about 40 meters apart. Inside the feedpoint enclosure are brushes from an electric drill to connect the elements to a 1:1 balun and a stepper motor to run the winch. As the wire pays out of one spool, the Dacron cord is taken up by the other; the same thing happens on the other side of the antenna, resulting in a balanced configuration.

We think this is a really clever design that should make many a ham happy across the bands. We even see how this could be adapted to other antenna configurations, like the end-fed halfwave we recently featured in our “$50 Ham” series.

A Hair-Raising Twist On Infinity Mirrors

February 10, 2021 by 6 Comments

Just when we thought we’d seen it all in the infinity mirror department, [FieldCrafting] blazed a tiny, shiny new trail with their electroplated infinity mirror hair pin. We’d sure like to stick this in our French twist. Fortunately, [FieldCrafting] provided step-by-step instructions for everything from the 3D printing to the copper electroplating to the mirror film and circuitry application.

And what tiny circuitry it is! This pin is powered by a coin cell and even has a micro slider switch to conserve it. The stick parts are a pair of knitting needles, which is a great idea — they’re pointy enough to get through hair, but not so pointy that they hurt.

[FieldCrafting] was planning to solder 1206 LEDs to copper tape and line the cavity with it, but somehow the CAD file ended up with 0603, so there wasn’t enough space for two tape traces. We think it’s probably for the better — [FieldCrafting]’s solution was to use two-conductor wire, strategically stripped, which seems a lot less fiddly than trying to keep two bare tape traces separated and passing pixies.

Don’t have enough hair for one of these? Surely you could use some handsome infinity coasters to round out that home bar setup.

Inflatable Hospital Isolation Wards

January 21, 2021 by 22 Comments

The continued spread of Covid-19 has resulted in a worldwide shortage of hospital beds. A temporary hospital isolation ward (translated) was co-developed by the Korea Advanced Institute of Science and Technology (KAIST) and the Korea Institute of Radiological and Medical Sciences (KIRAMS) to help alleviate this problem. We’re not familiar with the logistics and expense of installing traditional temporary hospital facilities, but the figures provided for this inflatable building approach to the problem seem impressive. It takes 14 days to produce one module, a process which presumably could be pipelined. Being 70% lighter and smaller than their rigidly-constructed counterparts, they can be more easily stored and shipped where needed, even by air.

Once on-site, it takes one day to inflate and outfit it with utilities such as electricity, water, and communications. One of these modules, which look like really big inflatable Quonset huts, contains an intensive care unit, four negative-pressure rooms, a nursing station, staff area, changing and bathrooms, and storage. All this in a 450 m2 building 30 m long and 15 m wide. That works out to be almost 2-stories tall, which is confirmed by the photo above.

Now that the design is finished and a functional unit constructed, the goal is to put it into production as soon as possible. Of course, physical hospital facilities are not the only thing in short supply these days — doctors, nursing and support staff, medical supplies, not to mention the vaccinations themselves, are all needed. But hopefully the success of this project can contribute to the global effort of saving lives and getting control of the virus sooner rather than later. The video below is in Korean, but the automatic English subtitles aren’t too bad.

Continue reading “Inflatable Hospital Isolation Wards” →

Serving The Feline Masters: A Chair To Follow The Sunny Spot

January 17, 2021 by 21 Comments

Terry Pratchett once wrote, “In ancient times cats were worshipped as gods; they have not forgotten this”. [Jonathan]’s cat has clearly not forgotten, and makes it loudly known whenever her favorite chair needs to be moved to stay in the spot of sunlight. He was looking for a fun hack anyway, so he decided to give in to her majesty’s demands, and automated the task.

[Jonathan] first considered adding motorizing the chair itself, but decided to keep it simple and just drag the chair across the room with a spool attached to a motor. The rope spool was attached to a small geared DC motor, mounted on a salad bowl base, and connected to an ESP8266 via a motor driver. The ‘8266 is running  NodeMCU with a web server that accepts simple motor commands through a RESTful API. This setup can’t reset the chair to it’s starting position at the end of the day, but this is a small price to pay for simplicity. The motor was a bit underpowered, but it only needed to move the chair in small distances at a time, so [Jonathan] removed the chair’s back to reduce the weight, and upped the motor voltage.

Determining when and how far to move the chair is the second part of the challenge. [Jonathan] considered a simple lookup table for the time of day, but the motor’s movement wasn’t consistent enough. The final solution was a set of three BH1750 digital ambient light sensors to give feedback. A pair of sensors on the chair determines its position relative to the sunny spot, by comparing light levels to a reference sensor mounted in the window. These light sensors are also attached to NodeMCUs, and send movement commands to the winding unit as necessary.

Continue reading “Serving The Feline Masters: A Chair To Follow The Sunny Spot” →

Inputs Of Interest: DecaTxt Ultra-Portable Chording Keyboard

January 5, 2021 by 33 Comments

Now here’s a stocking stuffer of a keyboard. The DecaTxt is the size of a deck of cards, and at first glance it looks like some kind of pocket Keno machine or other gambling or gaming apparatus. But that’s just because it’s so colorful. When you only have ten keys emulating a full keyboard, there’s bound to be some serious labeling going on, as there should be.

DecaTxt demonstration from IN10DID

The DecaTxt is a Bluetooth 4.0 chording keyboard that’s meant to be used with your phone or whatever you want to pair it with. It was originally called the In10did, which stands for Input Nomenclature Ten Digit Interface Device. Catchy, no? At some point in the last ten years, this little guy went wireless and got a cooler name — the DecaTxt. Continue reading “Inputs Of Interest: DecaTxt Ultra-Portable Chording Keyboard” →

Sinclair QL Repairs And Restoration

December 7, 2020 by 9 Comments

[Noel] was in possession of two non-working Sinclair QLs and made a series of videos about his attempts to repair and restore them. If you don’t remember the QL, it was a computer by the famous Clive Sinclair and while it was ahead of its time in some ways, it didn’t become as ubiquitous as some of its siblings or the IBM PC. It did, however, develop an almost cult-like following. You can see the trilogy of videos, below.

The machine was sophisticated for its day–after all, the QL was for quantum leap. Based on a Motorola 68008 processor running at 7.5 MHz, the QL included 128 KB of RAM and could handle up to 896 KB, a respectable amount for 1984. It even had a proprietary network interface. However, it was especially well known for having a pair of microtape drives. These were nicer than cassette tapes but perhaps not as handy as floppy disks. They were, however, cheaper to put into a computer. While there was an official operating system, it wasn’t long before most QL users switched to Minerva, a better OS.

Continue reading “Sinclair QL Repairs And Restoration” →

Zoombombing The EU Foreign Affairs Council

November 25, 2020 by 33 Comments

Those with security clearance are capable of making foolish mistakes, just like the rest of us. So is the story of how a Dutch journalist made an appearance on video meeting of the European Union’s Foreign Affairs Council (Dutch language, Google Translate link).

Ank Bijleveld's Tweeted picture, with the access details blacked out by Daniël Verlaan.
Netherlands Defence MInister Ank Bijleveld’s Tweeted picture, with the access details blacked out by Daniël Verlaan.

Like any other video call, if you had the link you could enter the meeting. So when Netherlands Defence Minister Ank Bijleveld Tweeted a photo of a video call last Friday, the address bar of the browser gave away the secret to anyone with a keen eye. Dutch journalist Daniël Verlaan working for the broadcaster RTL saw the URL on the screen and deduced the login credentials for the meeting.

We say “deduced”, but in fact there were five of the six digits in the PIN in the clear in the URL, leaving him with the difficult task of performing a one-digit brute-force attack and joining with the username “admin”. He joined and revealed his presence, then was admonished for committing a criminal offence before he left.

On one level it’s an opportunity for a good laugh at the expense of the defence ministers, and we certainly wouldn’t want to be Ank Bijleveld or probably the EU’s online security people once the inevitable investigation into this gets under way. It seems scarcely credible that the secrecy on such a high-security meeting could have sat upon such a shaky foundation without for example some form of two-factor authentication using the kind of hardware available only to governments.

EU policy is decided not by individual ministries but by delicate round-table summits of all 27 countries. In a pandemic these have shifted to being half-online and half in-real-life, so this EU defence ministers’ meeting had the usual mosaic video feed of politicians and national flags. And one Zoom-bombing journalist.