The $50 Ham: A Cheap Antenna For The HF Bands

January 19, 2021 by Dan Maloney 65 Comments

So far in the $50 Ham series, I’ve concentrated mainly on the VHF and UHF bands. The reason for this has to do mainly with FCC rules, which largely restrict Technician-level licensees to those bands. But there’s a financial component to it, too; high-frequency (HF) band privileges come both at the price of learning enough about radio to pass the General license test, as well as the need for gear that can be orders of magnitude more expensive than a $30 handy-talkie radio.

But while HF gear can be expensive, not everything needed to get on the air has to be so. And since it’s often the antenna that makes or breaks an amateur radio operator’s ability to make contacts, we’ll look at a simple but versatile antenna design that can be adapted to support everything from a big, powerful base station to portable QRP (low-power) activations in the field: the end-fed half-wave antenna.

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Start Your New Career In Robot Dance Choreography

January 19, 2021 by Roger Cheng 31 Comments

Boston Dynamics loves showing off their robots with dance videos. Every time they put one out, it ignites a discussion among robot enthusiasts debating what’s real versus merely implied by the exhibition. We really want to see tooling behind the scenes and fortunately we get a peek with a Spot dance choreography session posted by [Adam Savage]’s Tested team. (YouTube video, also embedded below.)

For about a year, the Tested team has been among those exploring a Spot’s potential. Most of what we’ve seen has been controlled from a custom tablet that looked like a handheld video game console. In contrast, this video shows a computer application for sequencing Spot actions on a music-focused timeline. The timer period is specified in beats per minute, grouped up eight to a bar. The high level task is no different from choreographing human dancers: design something that can be performed to music, delights your audience, all while staying within the boundaries of what your dancers can physically do with their bodies. Then, trust your dancers to perform!

That computer application is Boston Dynamics Choreographer, part of the Spot Choreography SDK. A reference available to anyone who is willing to Read The Fine Manual even if we don’t have a Spot of our own. As of this writing, Choreography SDK covers everything we saw Spot do in an earlier UpTown Funk dance video, but looks like it has yet to receive some of the more advanced Spot dances in the recent Do You Love me? video. There is a reference chart of moves illustrated with animated GIF, documented with customizable parameters along with other important notes.

We’ve seen a lot of hackers take on the challenge of building their own quadruped robots on these pages. Each full of clever mechanical design solutions that can match Spot’s kinematics. And while not all of them can match Spot’s control systems, we’re sure it’s only a matter of time before counterparts to Choreographer application show up on GitHub. (If they already exist, please link in comments.) Will we love robots once they can all dance? The jury is still out.

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Mavic Mini Gets Custom Clear Case

January 19, 2021 by Lewin Day 4 Comments

Apparently, in the drone scene, sticker wraps are popular for a custom aesthetic. [Useless Mod] wanted to go a little further, however, and decided to build a full crystal enclosure for his Mavic Mini, facing some hurdles along the way. (Video, embedded below.)

The first stage of the build was disassembly, with the compact 249 gram drone requiring a deft touch to avoid damaging the delicate ribbon cables and mechanisms inside. With the drone stripped down to its bare components, a silicone mould was made of each individual piece of the case, with new parts being cast in clear epoxy. It’s not a job for the faint of heart, with many undercuts and complex features to contend with. However, [Useless Mod] managed to produce the parts and get it all back together.

An initial test flight ended poorly, when the drone entered an uncontrollable wobble due to the case not being fully assembled. However, with fresh internals and with everything properly put together, everything worked! It’s not a build we’d suggest for the inexperienced, as the moulds required are complex and the electronics quite fragile. The final result is a good one though, and it even weighs 10 grams less than the original casing!

For those in the US, the world of drones is set to change drastically in short order.

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