We always think of [Scott Manley] as someone who knows a lot about rockets. So, if you think about it, it isn’t surprising he’s talking about GPS — after all, the system uses satellites. GPS is used in everything these days, and other forms of navigation are starting to fall by the wayside. However, the problem is that the system is vulnerable to jamming and spoofing. This is especially important if you fear GPS allowing missiles or drones to strike precise targets. But there are also plenty of opportunities for malicious acts. For example, drone light shows may be subject to GPS attacks from rival companies, and you can easily imagine worse. [Scott] talks about the issues around GPS spoofing in the video, which you can see below.
Since GPS satellites are distant, blocking the signal is almost too easy, sometimes happening inadvertently. GPS has technology to operate in the face of noise and interference, but there’s no way to prevent it entirely. Spoofing — where you produce false GPS coordinates — is much more difficult.
As desktop 3D printers have inched towards something resembling the mainstream, manufacturers have upped their game across the board. Even the quality of filament that you can get today is far better than what was on the market in the olden days, back when a printer made out of laser-cut birch wasn’t an uncommon sight at the local makerspace. Now, even the cheap rolls are wound fairly well and are of a consistent diameter. For most folks, you just need to pick a well-reviewed brand, buy a roll, and get printing.
But as with everything else, there are exceptions. Some people are producing their own filaments, or want to make sure their extrusion rate is perfectly calibrated. For those that need the capability, the WInFiDEL from [Sasa Karanovic] can detect filament diameter in real-time while keeping the cost and complexity as low as possible. Even better, with both the hardware and software released as open source, it makes an excellent starting point for further development and customization.
Although we usually imagine the conditions in Ancient Egypt to be much like the Egypt of today, back during the Holocene there was significantly more rain as a result of the African Humid Period (AHP). This translated in the river Nile stretching far beyond its current range, with many more branches. This knowledge led a team of researchers to test the hypothesis that the largest cluster of pyramids in the Nile Valley was sited along one of these now long since vanished branches. Their findings are described in an article published in Communications Earth & Environment, by [Eman Ghoneim] and colleagues.
The Ahramat Branch and pyramids along its trajectory. (Credit: Eman Ghoneim et al., 2024)
The CliffsNotes version can be found in the accompanying press release by the University of North Carolina Wilmington. Effectively, the researchers postulated that a branch of the Nile existed along these grouping of pyramids, with their accompanying temples originally positioned alongside this branch. The trick was to prove that a river branch once existed in that area many thousands of years ago.
What complicates this is that the main course of the Nile has shifted over the centuries, and anthropogenic activity has obscured much what remained, making life for researchers exceedingly difficult. Ultimately a combination of soil core samples, geophysical evidence, and remote sensing (e.g. satellite imagery) helped to cement the evidence for the existence what they termed the Ahramat Nile Branch, with ‘ahramat’ meaning ‘pyramids’ in Arabic.
Synthetic Aperture Radar (SAR) and high-resolution radar elevation data provided evidence for the Nile once having traveled right past this string of pyramids, also identifying the modern Bahr el-Libeini canal as one of the last remnants of the Ahramat Branch before the river’s course across the floodplain shifted towards the East, probably due to tectonic activity. Further research using Ground Penetrating Radar (GPR) and Electromagnetic Tomography (EMT) along a 1.2 km section of the suspected former riverbed gave clear indications of a well-preserved river channel, with the expected silt and sediments.
Soil cores to a depth of 20 and 13 meters further confirmed this, showing not only the sediment, but also freshwater mussel shells at 6 meter depth. Shallow groundwater was indicated at these core sites, meaning that even today subsurface water still flows through this part of the floodplain.
These findings not only align with the string of pyramids and their causeways that would have provided direct access to the water’s edge, but also provided hints for a further discovery regarding the Bent Pyramid — as it’s commonly known — which is located deep inside the desert today. Although located far from the floodplain by about a kilometer, its approximately 700 meters long causeway terminates at what would have been a now extinct channel: the Dahshur Inlet, which might also have served the Red Pyramid and others, although evidence for this is shakier.
Altogether, these findings further illustrate an Ancient Egypt where the Old Kingdom was followed by a period of severe changes, with increasing drought caused by the end of the AHP, an eastwardly migrating floodplain and decreased flow in the Nile from its tributaries. By the time that European explorers laid eyes on the ancient wonders of the Ancient Egyptian pyramids, the civilization that had birthed them was no more, nor was the green and relatively lush environment that had once surrounded it.
While it doesn’t look like a traditional robot, the hydrogel robot from [Zi Liang Wu] forms a möbius strip and can be activated by light. They also experimented with shaping the hydrogels as a Seifert ribbon.
The key is that the hydrogels contain gold nanoparticles. Light heats the gold particles and this causes the hydrogels to move. The connections between the strips of hydrogels causes them to move in predictable ways. You can see a video about the experiments below.
These robots aren’t going to be for warehouse or factory work. But they can do tasks like collecting plastic beads, something difficult for conventional robots to do. They also hope to demonstrate that these soft robots could work in the body for taking samples or delivering a drug, although it isn’t apparent how light would get to them inside your body.
The dark side of the material tends to turn towards the light. The continuous loop structure means it never runs to the end of its travel. Watching it move on a string is pretty impressive.
Crawling and slithering robots may be the answer for certain specialized applications. After all, it works well in nature.
Something that all radio amateurs encounter sooner or later is the subject of impedance matching. If you’d like to make sure all that power is transferred from your transmitter into the antenna and not reflected back into your power amplifier, there’s a need for the impedance of the one to match that of the other. Most antennas aren’t quite the desired 50 ohms impedance, so part of the standard equipment becomes an antenna tuner — an impedance matching network. For high-power hams these are big boxes full of chunky variable capacitors and big air cored inductors, but that doesn’t exclude the low-power ham from the impedance matching party. [Barbaros Aşuroğlu WB2CBA] has designed the perfect device for them: the credit card ATU.
The circuit of an antenna tuner is simple enough, two capacitors and an inductor in a so-called Pi-network because of its superficial resemblance to the Greek letter Pi. The idea is to vary the capacitances and inductance to find the best match, and on this tiny model it’s done through a set of miniature rotary switches. There are a set of slide switches to vary the configuration or switch in a load, and there’s even a simple matching indicator circuit.
Apple is fairly notorious for building devices that are difficult to repair, but with the right tools it’s often not completely impossible to circumvent some of their barriers. As they say, every lock has a key. [dosdude1] has wanted a specific M1 development board for a while now and has been slowly piecing together everything he needs to cobble one together, and finally got this unit running despite many roadblocks put in his way by Apple.
The development kit is a Developer Transition Kit or “DTK” meant for developers during Apple’s transition from Intel chips to their own in-house ARM-based M1 platform. This particular version is in a Mac Mini form factor but it has a few hurdles to clear before it powers on. First, the board was cut in a critical location that shorted out many of the PCB layers, so this had to be carefully filed down to remove the shorts. It was also missing a few tiny surface mount components and a NAND chip, but these were scavenged from other scrapped parts and assembled into a fully working machine.
There are a number of other non-physical problems to solve here as well, too. Apple coded their NAND chips to work with specific WiFi modules so if these aren’t programmed to work together the computer will get stuck in a boot loop. But with that and a few other details out of the way [dosdude1] finally has his DTK up and running in a 2018 Mac Mini chassis, right down to the working power LEDs. We’ve seen all kinds of PCB damage before (although not often quite this intricate) and even PCBs repaired that were snapped in half.
We are big fans of programmed texts for education. You know, the kind where you answer a question and go to a new page based on your answer. But they can also be entertaining “choose your own adventure” stories. You might say, “You are standing in front of an oak door, two meters high, with an iron handle. Do you a) open it? b) knock on it? c) ignore it?” Then, based on your answer, you go to a different part of the story. These are tough to write, but you can get some help using Yarn Spinner and the Yarn scripting language.
The original purpose of Yarn is to produce conversations for games. There’s a tutorial for that. The difference is to produce a book, you get a choose your own adventure PDF at the end. For the tutorial, you can try to read the text on the left-hand side of the editor or just press Test (at the top) and let it “read” the tutorial to you, which is a little more fluid.
