Author: Dan Maloney

3211 Articles

Growing Simple Crystals For Non-Linear Optics Experiments

July 6, 2023 by 18 Comments

Here’s an exercise for you: type “crystals” into your favorite search engine and see what you get. If you’re anything like us, you’ll get a bunch of pseudoscientific posts about the healing power of crystals, along with offers to buy the same at exorbitant prices. But woo-woo aside, certain crystals do have seemingly magical powers — like the ability to turn light from one color into another.

None of this is magic, of course. Rather, as optics aficionado [Les Wright] explains, non-linear optics is all about physics. Big physics, too, like the kind that made the National Ignition Facility the first fusion research outfit to reach the “break-even” point, at least in terms of optical energy. To do so, they need to convert megajoules of infrared laser beams all the way across the visible spectrum into the ultraviolet, relying on huge crystals of deuterated potassium dihydrogen phosphate (KDP) to do so. Depending on how they’re cut, crystals of these sorts have non-linear optical properties like second-harmonic generation, which combines two input photons into a single output photon with twice the energy of the original. This results in a halving of the wavelength of the input, which doubles the frequency.

While the process used at the NIF produces crystals of enormous proportions, [Les] has more modest needs and thus a simpler process. His KDP is an off-the-shelf chemical, nothing fancy about it, which is added to boiling water to make a saturated solution. A little of the solution is poured out into a watch glass to make seed crystals, and everything is allowed to cool slowly. A nice seed crystal is glued to a piece of monofilament fishing line and suspended in the saturated solution, and with enough time a good-sized crystal forms. Placed into the beam path of a 1,064 nm IR laser and rotated carefully relative to the beam, the crystal easily produces a brilliant green laser output.

This is fascinating stuff, and we’re looking forward to seeing where [Les] goes with this. Polishing the crystals to make them optically cleaner would be a good next step, as would perhaps growing even larger crystals.

Continue reading “Growing Simple Crystals For Non-Linear Optics Experiments” →

Minimal Mods Make Commodity LNBs Work For QO-100 Reception

July 4, 2023 by 15 Comments

A word of advice: If you see an old direct satellite TV dish put out to the curb, grab it before the trash collector does. Like microwave ovens, satellite dishes are an e-waste wonderland, and just throwing them away before taking out the good stuff would be a shame. And with dishes, the good stuff basically amounts to the bit at the end of the arm that contains the feedhorn and low-noise block downconverter (LNB).

But what does one do with such a thing once it’s harvested? Lots of stuff, including modifying it for use with the QO-100 geosynchronous satellite (German link). That’s what [Sebastian Westerhold] and [Celin Matlinski] did with a commodity LNB, although it seems more like something scored on the cheap from one of the usual sources rather than picking through trash. Either way, these LNBs are highly integrated devices that at built specifically for satellite TV use, but with just a little persuasion can be nudged into the K-band to receive the downlink signals from hams using QO-100 as a repeater.

The mods are simple — snipping out the 25 MHz reference crystal on the LNB board and replacing it with a simple LC bandpass filter. This allows the local oscillator on the LNB to be referenced to an external signal generator; when fed with a 25.78 MHz signal, it’s enough to goose the LNB up to 10,490 MHz — right about the downlink frequency. [Sebastian] and [Celin] tested the mods and found that it was easily able to detect the third harmonics of a 3.5-ish GHz signal.

As for testing on actual downlink signals from the satellite, that’ll have to wait. For now, if you’re interested in satellite comms, and you live on the third of the planet covered by QO-100, keep an eye out for those e-waste LNBs and get to work.

3D Printing Food Hack Chat

July 3, 2023 by 1 Comment

Join us on Wednesday, July 5 at noon Pacific for the 3D Printing Food Hack Chat with Ellie Weinstein!

In the right hands, food goes beyond mere sustenance and becomes a work of art. We’ve all seen examples — the carefully crafted blends of flavors, the quality ingredients expertly cooked, the artful platings that make a dramatic presentation at the table. But where the artistry really seems to take off is with desserts, which pastry chefs and confectioners can take to the next level with edible sculptures of chocolate and other sweets that can tower dramatically over the table.

join-hack-chatThat’s all well and good for the haute cuisine set, but what about the rest of us? We can’t all have the talent and drive needed to produce edible art, so perhaps we can leverage technology to help us out. That’s just one of the rationales behind food 3D printing, which is what we’ll be exploring with Ellie Weinstein. She’s the CEO of Cocoa Press, where they’re bringing chocolate 3D printing to the mainstream. It’s not as easy as you might think — there are plenty of nuances and engineering challenges when you’re trying to print chocolate or any other kind of food. Make sure you stop by and check it out; it’s sure to be a treat.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, July 5 at 12:00 PM Pacific time. If time zones have you tied up, we have a handy time zone converter.

Hackaday Links Column Banner

Hackaday Links: July 2, 2023

July 2, 2023 by 21 Comments

Members of Pixelbar woke up to shocking news on Wednesday morning this week as they learned that a fire had destroyed the building housing their Rotterdam hackerspace. Pictures of the fire are pretty dramatic and show the entire building ablaze. We’re not familiar with Pixelbar specifically, but most hackerspaces seem to share space with other businesses in repurposed warehouses and other industrial buildings, and it looks like that was the case here. Local coverage doesn’t indicate that a cause has been determined, but they do say that “large batches of wood” were stored in or near the structure, which likely contributed to the dramatic display. There don’t seem to be reports of injuries to civilians or first responders, so that’s a blessing, but Pixelbar seems to have been completely destroyed. If you’re in a position to help, check out their GoFundMe page. As our own Jenny List, who currently lives in The Netherlands, points out, spaces suitable for housing a hackerspace are hard to come by in a city like Rotterdam, which is the busiest port in Europe. That means Pixelbar members will be competing for space with businesses that have far deeper pockets, so anything you can donate will likely go a long way toward rebuilding.

Continue reading “Hackaday Links: July 2, 2023” →

A Quick And Easy Tape Measure Turnstile Antenna For MILSAT Snooping

June 30, 2023 by 16 Comments

The number of satellites whizzing by over our heads at any moment is staggering, and growing at a rapid rate as new constellations are launched. But sometimes it’s the old birds that are the most interesting, as is the case with some obsolete but still functional military communications satellites, which thanks to a lack of forethought are largely unsecured and easily exploitable. And all that’s needed to snoop in on them is a cheap ham radio and something like this simple and portable satcom antenna.

As proof of the global nature of the radio hobby, the design in the video below by Brit [Tech Minds] borrows heavily from previous work by Italian ham [Ivo Brugnera (I6IBE)], which itself was adapted to use 3D-printed parts in a German blog post a few years ago. The common thread is the use of tape measures for the elements of the aptly named turnstile antenna, a tried and true material for lightweight, foldable antennas that amateur radio enthusiasts have been using for years. The antenna is similar in design to the classic three-element Yagi-Uda, with a crossed pair of driven elements in the middle of a boom that also supports a reflector and a director. Strips of tape measure material are held to the 20-mm aluminum tubing boom with 3D-printed brackets. A phasing harness of precisely cut coax cable connects to the driven elements and runs down the boom; the quarter-wavelength loop serves to introduce the 90° phase shift needed for the circularly polarized signal from the satellites.

A quick scan with a vector antenna analyzer showed just how well this antenna performs on the 220-MHz band, and the antenna was easily able to pick up the Brazilian satellite pirate’s chatter. The tape measure elements make the antenna easy to handle and foldable, not to mention pretty cheap to build. And what’s not to love about that?

Continue reading “A Quick And Easy Tape Measure Turnstile Antenna For MILSAT Snooping” →

Spy Radio Setup Gets A Tiny Power Supply For Field Operations

June 29, 2023 by 14 Comments

[Helge Fyske (LA6NCA)] may not be an actual spy — then again, he may be; if he’s good at it, we wouldn’t know — but he has built a couple of neat vacuum tube spy radios in the past. And there’s no better test for such equipment than to haul it out into the field and try to make some contacts. But how do you power such things away from the bench?

To answer that question, skip ahead to the 3:18 mark of the video below, where [Helge] shows off his whole retro rig, including the compact 250-volt power supply he built for his two-tube 80-m Altoids tin spy transceiver. In the shack, [Helge] powers it with a bench power supply of his own design to provide the high anode voltage needed for the tubes, as well as 12 volts for their heaters. Portable operations require a more compact solution, preferably one that can be run off a battery small enough to pack in.

By building his power supply in a tin, [Helge] keeps to his compact build philosophy. But the circuit is all solid state, which is an interesting departure for him. The switch-mode supply uses a 4047 astable multivibrator chip as a 50-kHz oscillator, which switches back and forth between a pair of MOSFETs to drive a transformer. This steps up the 12-volt input to 280 volts AC, which is then rectified, filtered, and regulated to 250 volts DC.

To round out his spy rig, [Helge] also designed a tiny Morse key, which appears to be 3D printed and fits in its own tin, and a compact dipole antenna. Despite picking what appears to be a challenging location — the bottom of a steep-sided fjord — [Helge] was easily able to make contacts over a distance of 400 km. His noise floor was remarkably low, a testament to the solid design of his power supply. Including the sealed lead acid battery, the whole kit is compact and efficient, and it’s a nice example of what vacuum tubes and solid state can accomplish together.

Continue reading “Spy Radio Setup Gets A Tiny Power Supply For Field Operations” →

Know Snow: Monitoring Snowpack With The SNOTEL Network

June 29, 2023 by 13 Comments

With summer just underway here in North America, it may seem like a strange time to talk about snow. But when you live in North Idaho, winter is never very far away and is always very much on everyone’s mind. Our summers are fierce but all too brief, so starting around September, most of us begin to cast a wary eye at the peaks of the Bitterroot range in the mornings, looking for the first signs of snow. And in the late spring, we do much the same, except longingly looking for the first signs that the snowpack is finally breaking up.

We all know how important snow is, of course. Snow is our lifeline, nearly the only source of drinking water we have here, as well as the foundation of our outdoor recreation industries. We also know that the snowpack determines our risk for wildfires, so while the long, dark winters may take a psychological toll, the longer the snow stays on the mountains, the less chance we have of burning come summer.

These are all very subjective measures, though, and there’s way too much riding on the snowpack to leave it up to casual observation. To make things more quantitative, the US Department of Agriculture’s Natural Resources Conservation Service (NRCS) has built a system across the western US that measures the snowpack in real-time, and provides invaluable data to climatologists, fish and game managers, farmers, and even the recreation industry, all of whom have a vested interest in the water held within. The network is called SNOTEL, and I recently got a chance to take a field trip with a hydrologist and get an up-close look at how it works.

Continue reading “Know Snow: Monitoring Snowpack With The SNOTEL Network” →