Since 2010, the United States military has been operating a pair of small reusable spaceplanes that conduct secretive long-duration flights in low Earth orbit. Now officially operating under the auspices of the newly formed Space Force, the X-37Bs allow the military to conduct in-house research on new hardware and technology with limited involvement from outside agencies. The spaceplane still needs to hitch a ride to space on a commercial rocket like the Atlas V or the Falcon 9, but once it’s separated from the booster, the remainder of the X-37B’s mission is a military affair.
So naturally, there’s a lot we don’t know about the USSF-7 mission that launched from Cape Canaveral Air Force Station on May 17th. The duration of the mission and a complete manifest of the experiments aboard are classified, so nobody outside the Department of Defense truly knows what the robotic spacecraft is up to. But from previous missions we know the craft will likely remain in orbit for a minimum of two years, and there’s enough public information to piece together at least some of the investigations it will be conducting.
Certainly one the most interesting among them is an experiment from the U.S. Naval Research Laboratory (NRL) that will study converting solar power into a narrow microwave beam; a concept that has long been considered the key to unlocking the nearly unlimited energy potential offered by an orbital solar array. Even on a smaller scale, a safe and reliable way to transmit power over the air would have many possible applications. For example it could be used to keep unmanned aerial vehicles airborne indefinitely, or provide additional power for electric aircraft as they take-off.
Performing an orbital test of this technology is a serious commitment, and shows that all involved parties must have a fairly high confidence level in the hardware. Unfortunately, there isn’t much public information available about the power beaming experiment currently aboard the X-37B. There’s not even an indication of when it will be performed, much less when we should expect to see any kind of report on how it went. But we can make some educated guesses based on the work that the Naval Research Laboratory has already done in this field.
When getting parts together for a one-off project, we often find ourselves with some leftovers on hand. Most of the time these things go in the junk drawer, but [Brad] aka [AtomicZombie] was working on a project which required parts salvaged from several microwave ovens. That left him with enough surplus components to build a social distancing enforcement tool for the modern age; which will deliver a taser-like shock to anyone which violates the new six-foot rule.
The leftover parts in question were built around a high-voltage capacitor, which [Brad] strapped to his back to hold all of the electronics needed for the six-foot electrified hoop. The generator utilizes the output voltage from two magnetrons, but doesn’t start until the operator enters a code on the front control panel, which is about the only safety device on this entire contraption. To get power to the magnetrons a 12 VDC car battery is used with an inverter to get the required input voltage, and towards the end of the video linked below he shows its effectiveness by setting various objects on fire with it.
While this gag project is unlikely to get any actual use, it’s not like any of us around here need an excuse to play with high voltages. [Brad] is also unlikely to need it either; he lives on a secluded 100-acre homestead and has been featured here for some of the projects he built to make his peaceful life a little easier, like a robotic laundry line, mobile chicken coop, and an electric utility tricycle built from an old truck and motorcycle.
[hclxing] eagerly picked up an LED ceiling light for its ability to be turned on and off remotely, but it turns out that the lamp has quite a few other features. These include adjustable brightness, color temperature, automatic turnoff, light sensing, motion sensing, and more. Before installing, [hclxing] decided to tear it down to see what was involved in bringing all those features to bear, but after opening the lamp there wasn’t much to see. Surprisingly, besides a PCB laden with LEDs, there were exactly two components inside the unit: an AC power adapter and a small white controller unit. That’s it.
The power adapter is straightforward in that it accepts 100-240 Volts AC and turns it into 30-40 Volts DC for the LEDs, and it appears to provide 5 V for the controller as well. But [hclxing] noticed that the small white controller unit — the only other component besides the LEDs — had an FCC ID on it. A quick bit of online sleuthing revealed that ID is attached to a microwave sensor module. Most of us would probably expect to see a PIR sensor, but this light is motion sensing with microwaves. We have seen such units tested in the past, which links to a video [hclxing] also references.
The microwave motion sensor board is shown here, and underneath it is a dense PCB that controls all other functions. Once [hclxing] identified the wires and their signals, it was off to Costco to buy more because the device looks eminently hackable. We’re sure [hclxing] can do it, given their past history with reverse-engineering WyzeSense hardware.
If a grizzled RF engineer who bears the soldering-iron scars of a thousand projects could offer any advice, it would be that microwave antennas are not a field to be entered into lightly. Much heartache is to be saved by using an off-the-shelf design, and only the foolhardy venture willingly down the stripline into the underworld of complex microwave resonances.
But every would-be microwave designer has to start somewhere, and for [Adam Gulyas] that start came with a 2.4 GHz patch antenna. His write-up is a fascinating tale of the challenges and pitfalls of creating something which is deceptively simple at first sight but which becomes significantly more complex as he characterizes his design made real as a PCB.
The process started with a set of calculations to derive the patch dimensions and a bit of PCB work adding a stripline feed. This was produced on a PCB, a normal 1.6mm thick FR4 fiberglass board. When hooked up to a VNA its impedance was all wrong. Further, it had a resonance at the required frequency but also unexpected ones at 3.7 and 4.6 GHz. Simulation of the design also yielded a different resonance from the one calculated, and discussing it with others yielded the conclusion that the feed might be at fault. He ended up using an inset feed, with a co-axial cable emerging away from the edge of the patch, and was able to achieve a far better result.
We can all learn something from [Adam]’s write-up, and we salute him for staying the course to get the design to a usable point. It would be interesting to see the same antenna produced from a more consistent dielectric material than generic FR4. Meanwhile, if you are interested in microwave RF design, take a look at Michael Ossmann’s primer on the subject.
Ecclesiastes 1:9 reads “What has been will be again, what has done will be done again; there is nothing new under the sun.” Or in other words, 5G is mostly marketing nonsense; like 4G, 3G, and 2G was before it. Let’s not forget LTE, 4G LTE, Advance 4G, and Edge.
Technically, 5G means that providers could, if they wanted to, install some EHF antennas; the same kind we’ve been using forever to do point to point microwave internet in cities. These frequencies are too lazy to pass through a wall, so we’d have to install these antennas in a grid at ground level. The promised result is that we’ll all get slightly lower latency tiered internet connections that won’t live up to the hype at all. From a customer perspective, about the only thing it will do is let us hit the 8Gb ceiling twice as faster on our “unlimited” plans before they throttle us. It might be nice on a laptop, but it would be a historically ridiculous assumption that Verizon is going to let us tether devices to their shiny new network without charging us a million Yen for the privilege.
So, what’s the deal? From a practical standpoint we’ve already maxed out what a phone needs. For example, here’s a dirty secret of the phone world: you can’t tell the difference between 1080p and 720p video on a tiny screen. I know of more than one company where the 1080p on their app really means 640 or 720 displayed on the device and 1080p is recorded on the cloud somewhere for download. Not a single user has noticed or complained. Oh, maybe if you’re looking hard you can feel that one picture is sharper than the other, but past that what are you doing? Likewise, what’s the point of 60fps 8k video on a phone? Or even a laptop for that matter?
Are we really going to max out a mobile webpage? Since our device’s ability to present information exceeds our ability to process it, is there a theoretical maximum to the size of an app? Even if we had Gbit internet to every phone in the world, from a user standpoint it would be a marginal improvement at best. Unless you’re a professional mobile game player (is that a thing yet?) latency is meaningless to you. The buffer buffs the experience until it shines.
So why should we care about billion dollar corporations racing to have the best network for sending low resolution advertising gifs to our disctracto cubes? Because 5G is for robots.
One of the great things about ham radio is that isn’t just one hobby. Some people like to chit chat, some like to work foreign countries, some prepare for emergencies, and there are several space-related activities. There are hundreds of different kinds of activities to choose from. Just one is moonbounce, and [Ham Radio DX] decided to replicate a feat many hams have done over the years: communicate with someone far away by bouncing signals from the moon.
The set up is pretty sophisticated but not as bad as you might imagine. You can see that they spend a lot of time getting the equipment aligned. A known reference point helps them set the position of the antenna. A GPS keeps both stations in sync for frequency and time.
Synthetic-aperture radar, in which a moving radar is used to simulate a very large antenna and obtain high-resolution images, is typically not the stuff of hobbyists. Nobody told that to [Henrik Forstén], though, and so we’ve got this bicycle-mounted synthetic-aperture radar project to marvel over as a result.
Neither the electronics nor the math involved in making SAR work is trivial, so [Henrik]’s comprehensive write-up is invaluable to understanding what’s going on. First step: build a 6-GHz frequency modulated-continuous wave (FMCW) radar, a project that [Henrik] undertook some time back that really knocked our socks off. His FMCW set is good enough to resolve human-scale objects at about 100 meters.
Moving the radar and capturing data along a path are the next steps and are pretty simple, but figuring out what to do with the data is anything but. [Henrik] goes into great detail about the SAR algorithm he used, called Omega-K, a routine that makes use of the Fast Fourier Transform which he implemented for a GPU using Tensor Flow. We usually see that for neural net applications, but the code turned out remarkably detailed 2D scans of a parking lot he rode through with the bike-mounted radar. [Henrik] added an auto-focus routine as well, and you can clearly see each parked car, light pole, and distant building within range of the radar.
We find it pretty amazing what [Henrik] was able to accomplish with relatively low-budget equipment. Synthetic-aperture radar has a lot of applications, and we’d love to see this refined and developed further.