Toshiro Kodera: Electromagnetic Gyrotropes

We’ve learned a lot by watching the talks from the Hackaday Superconferences. Still, it’s a rare occurrence to learn something totally new. Microwave engineer, professor, and mad hacker [Toshiro Kodera] gave a talk on some current research that he’s doing: replacing natural magnetic gyrotropic material with engineered metamaterials in order to make two-way beam steering antennas and more.

If you already fully understood that last sentence, you may not learn as much from [Toshiro]’s talk as we did. If you’re at all interested in strange radio-frequency phenomena, neat material properties, or are just curious, don your physics wizard’s hat and watch his presentation. Just below the video, we’ll attempt to give you the Cliff’s Notes.

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RainCube Spreads Its Umbrella

There are times when a mechanism comes to your attention that you have to watch time and time again, to study its intricacies and marvel at the skill of its designer. Sometimes it can be a complex mechanism such as a musical automaton or a mechanical loom, but other times it can be a device whose apparent simplicity hides its underlying cleverness. Such a moment came for us today, and it’s one we have to share with you.

RainCube is a satellite, as its name suggests in the CubeSat form factor and carrying radar instruments to study Earthly precipitation. One of the demands of its radar system is a parabolic dish antenna, and even at its 37.5 GHz  that antenna needs to be significantly larger than its 6U CubeSat chassis.

The unfolding parabola in action.
The unfolding parabola in action.

It is the JPL engineers’ solution to this problem that is the beautiful mechanism we want to show you. The parabola is folded within itself and tightly furled round the feedhorn within the body of the satellite. As the feedhorn emerges, first the inner sections unfurl and then the outer edge of the parabola springs out to form the dish antenna shape. Simultaneously a mechanism of simplicity, cleverness, and beauty, one we’d be very proud of if it were our creation.

There is nothing new in collapsible parabolas used in spacecraft antennas, petal and umbrella-like designs have been a feature of some of the most famous craft. But the way that this one has been fitted into such a small space (and so elegantly) makes it special, we hope you’ll agree.


Start Your Path to Becoming an Antenna Guru

We’ve known a few people over the years that have some secret insight into antennas. To most of us, though, it is somewhat of a black art (which explains all the quasi-science antennas made out of improbable elements you can find on the web). There was a time when only the hams and the RF nerds cared about antennas, but these days wireless is everywhere: cell phones, WiFi, Bluetooth, and even RF remote controls all live and die based on their antennas.

You can find a lot of high-powered math discussions about antennas full of Maxwell’s equations, spherical integration and other high-power calculus, and lots of arcane diagrams. [Mark Hughes] recently posted a two-part introduction to antennas that has less math and more animated images, which is fine with us (when you are done with the first part, check out part two). He’s also included a video which you can find below.

The first part is fairly simple with a discussion of history and electromagnetics. However, it also talks about superposition, reflection, and standing wave ratio. Part two, though, goes into radiation patterns and gain. Overall, it is a great gateway to a relatively arcane art.

We’ve talked about Smith charts before, which are probably the next logical step for the apprentice antenna wizard. We also covered PCB antenna design.

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Glow-In-The-Dark Antenna Helps You Spot Your Car At Night

It’s late, and you’re lost in a sea of cars trying to remember where you parked. If only your vehicle had a glow-in-the-dark antenna to make it easier to find, you wouldn’t be in this situation. Faced with just such a problem himself, Instructables user [botzendesign] has put together a handy tutorial to do just that.

[botzendesign] first removed the antenna and lightly abraded it to help the three coats adhesion promoter do its job. A white base coat of vehicle primer was applied — lightly, so it doesn’t crack over time — and once it had set, three coats of Plasti Dip followed. Before that had a chance to dry, he started applying the glow-in-the-dark powder, another coat of Plasti Dip, repeating four more times to ensure the entire antenna had an even coat of the photo-luminescent powder and then letting it dry for 24 hours. Continue reading “Glow-In-The-Dark Antenna Helps You Spot Your Car At Night”

Pneumatic Launcher Gets Ham Antennas Hanging High

Amateur radio is an eclectic hobby, to say the least. RF propagation, electrical engineering, antenna theory – those are the basics for the Ham skillset. But pneumatics? Even that could come in handy for hanging up antennas, which is what this compressed-air cannon is designed to do.

[KA8VIT]’s build will be familiar to any air cannon aficionado. Built from 2″ Schedule 40 PVC, the reservoir is connected to the short barrel by a quarter-turn ball valve. Charging is accomplished through a Schrader valve with a cheap little tire inflator, and the projectile is a tennis ball weighted with a handful of pennies stuffed through a slit. Lofting an antenna with this rig is as simple as attaching a fishing line to the ball and using that to pull successively larger lines until you can pull the antenna itself. [KA8VIT] could only muster about 55 PSI and a 70′ throw for the first attempt shown below, but a later attempt with a bigger compressor got him over 100 feet. We’d guess that a bigger ball valve might get even more bang for the buck by dumping as much air as quickly as possible into the chamber.

Looking to launch a tennis ball for non-Ham reasons? We’ve got you covered whether you want to power it with butane or carbon dioxide.

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Would You Like a Satellite Dish?

Satellite dishes are a common site these days, although admittedly most of them are Ku- and Ka-band dishes. The older C-band dishes are still around, though, just less frequently in people’s yards. [Greenish Apple] decide to cut the cable and start watching free TV so he built a C-band dish. The trick is, he made the dish out of wood.

The design is the offset type, not a prime focus dish–that is, the electronics are not in the center of the dish but on the side. Wood isn’t particularly good at reflecting RF, of course, so over the wooden skeleton, he used flashing.

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Ham Antenna Rises to the Occasion

There was a time when you could do what you wanted in your yard and hams could build giant antenna farms. These days, there are usually laws or deed restrictions that stop that from happening. Even if you can build an antenna, you might want to quickly put up something temporary in an emergency.

[Eric’s] solution? Suspend a wire from a weather balloon filled with helium from the local WalMart. The 8 foot balloon took two containers (18 cubic feet) of gas before it would rise sufficiently. Once you have a floating balloon, the rest of the concept is simple: connect a wire (100 feet of 26 gauge), use a tuner to match the load to the transmitter, and you have instant antenna.

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