One of amateur radio’s many interests comes in portable operation, taking your radio to an out of the way place, usually a summit, and working the world using only what can be carried in. Often this means using the HF or shortwave bands, but the higher frequencies get a look-in as well. A smaller antenna is no less the challenge when it comes to designing one that can be carried though, and [Thomas Witherspoon] demonstrates this with a foldable loop antenna for the 2 metre band.
The antenna provides a reminder that the higher bands are nothing to be scared of in construction terms, it uses a BNC-to-4 mm socket adapter as its feedpoint, and makes the rectangular shape of the loop with pieces of fiberglass tube. The wire itself is flexible antenna wire, though we’re guessing almost any conductor could be used. The result is a basic but useful antenna that certainly packs down to a very small size, and we can see it would be a useful addition to any portable operator’s arsenal.
Data science is a relatively new term for a relatively old discipline. Essentially, it is data analysis, particularly for large data sets. It involves techniques as wide-ranging as statistics, computer science, and information theory. What to know more? Stanford has a “Data Science Handbook” that you can read online.
Topics range from how to design a study and create an analytic plan to how to do data visualization, summarization, and analysis. The document covers quite a bit but is very concise.
What’s the worst part about packaging up a whole lot of the same basic thing? It might just be applying the various warning stickers to the outside of the shipping box. Luckily, [Mr Innovative] has built an open-source automatic sticker dispenser that does the peeling for you, while advancing the roll one at a time quite satisfyingly.
This tidy build is made primarily of 20×20 extruded aluminium and stainless steel smooth rod. All the yellow bits are 3D printed. The brains of this operation is an Arduino Nano, with an A4988 stepper motor driver controlling a NEMA17.
Our favorite part of this build is the IR sensor pair arranged below the ready sticker. It detects when a sticker is removed, then the stepper advances the roll by one sticker height. The waste is collected on a spool underneath.
Between the video and the instructions, [Mr Innovative] has made it quite simple to build one for yourself. Definitely check this one out after the break.
If you are reading this on an IBM PC-compatible computer, it is a certainty that its graphics card will support the lowest common denominator of PC displays, the Monochrome Display Adapter, or MDA. This was a video card which delivered a text-only display in black-and-white that was an option fitted to the very first PC models. But was it really a monochrome display adapter? [TubeTimeUS] is here to show us that when connected to the appropriate colour monitor, it can produce text in colour. It seems that this was a feature only on the very earliest revisions of the card.
Reading up on the MDA card, we find that at its heart it had a Motorola MC6845 CRT controller, a chip that appeared in a huge variety of machines from that era. The beauty of this chip was that it provided the correct timing signals and memory locations for video to be created, but didn’t include any video circuitry thus the designer was free to craft a video device to their specification, allowing for it to appear in both colour and monochrome devices. While the MDA card only supported a text mode it seems its designers managed to put in some form of colour attribute support even if it was never marketed as such. We’re not students of IBM graphics card modes here at Hackaday, but it would be fascinating to know whether this undocumented mode works in the same way from the software side as the colour text modes on CGA and better colour cards.
Before the Internet, if you wanted to hear news from around the world, you probably bought a shortwave receiver. In the golden age of world band radio, there was a great deal of high-quality programming on the shortwave bands and a large variety of consumer radios with shortwave bands. For example, the Sony CRF-160 that [M Caldeira] is restoring dates from the late 1960s or early 1970s and would have been a cool radio in its day. It retailed for about $250 in 1972, which sounds reasonable, but — don’t forget — in 1972 that would have been a 10% downpayment on a new car or enough to buy a Big Mac every day for a year with change left over.
As you can see in the video below, the radio seemed to work well right out of the gate, but the radio needed some rust removal and other sprucing up. However, it is an excellent teardown, with some tips about general restoration.
Amidst all the (well-deserved) hype around graphene, it’s important to remember that its properties are not unique to carbon. More atoms can be coaxed into stable 2-dimensional configuration, with molybdenene previously theoretically possible. This is now demonstrated by Tumesh Kumar Sahu and colleagues in a recent Nature Nanotechnology article, through the manufacturing of a 2D molybdenum-based material which they showed to be indeed molybdenene. Essentially, this is a 2D lattice of molybdenum atoms, a configuration in which it qualifies as Dirac matter, just like graphene. For those of us unfamiliar with Dirac materials, this gentle introduction by Jérôme Cayssol in Comptes Rendus Physique might be of use.
In order to create molybdenene, the researchers started with molybdenum disulfide (MoS2), which using a microwave-assisted field underwent electrochemical transformation into whiskers that when examined turned out to consist out of monolayers of Mo. The sulfur atoms were separated using a graphene sheet. As is typical, molybdenene sheets were exfoliated using Scotch tape, in a process reminiscent of the early days of graphene research.
Much like graphene and other Dirac materials, molybdenene has many potential uses as a catalyst, as cantilever in scanning electron microscope (SEM) tips, and more. If the past decades of research into graphene has demonstrated anything, it is that what once seemed more of a novelty, suddenly turned out to have endless potential in fields nobody had considered previously. One of these being as coatings for hard disk platters, for example, which has become feasible due to increasingly more efficient ways to produce graphene in large quantities.