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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Apple II Prints Off The Breaking News

January 18, 2021 by Lewin Day 18 Comments

These days, we’re alerted to the rise of Bitcoin and the fall of nations via little buzzes from the smartphones in our pocket. Go back fifty years or so and it was all a bit more romantic, with noisy teletype machines delivering hot tips straight to the newsroom for broadcast to the wider public. [Joshua Coleman] wanted a bit of that old fashioned charm, so set up a news printer at home with his old Apple II.

The Apple II in this case isn’t directly connected to the Internet. Instead, it talks to a modern Macintosh, acting as a serial terminal. The Macintosh then connects to a modern BBS that delivers news headlines over Telnet. The Apple II then routes the headlines as they come in to a beautiful Epson LQ-500 dot matrix printer, replete with vintage tractor feed paper. [Joshua] takes the time to highlight just what hardware is required, as well as how to set up the Apple II to redirect the serial output to the printer so the news automatically prints as it comes in.

It’s a fun and noisy way to stay up to date, and you can be sure that if you hear the printer really start going for it, you might want to switch on the TV for more information on just what’s going wrong at the present minute. Old computers may not have the grunt to really hang with the modern net, but they can make a charming interface for it; this SE/30 does a great job with Spotify, as an example. Video after the break.

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Q Multiplier — Er… Multiplies Q

January 18, 2021 by Al Williams 13 Comments

If you are below a certain age, you’ve probably never heard of a Q multiplier. This is a device that increases the “Q” of a radio receiver’s intermediate frequency and, thus, provide a higher selectivity. If you enjoy nostalgia, you can see inside a 1960s-era Heathkit QF-1 Q multiplier in [Jeff’s] informative video, below.

The Q multiplier was a regenerative amplifier that operated at just below the oscillation point. This provided very high amplification for the frequency of interest and less amplification for other frequencies. Some radios had a stage like this built-in, but the QF-1 was made to add into an external radio. For some Heathkit receivers, there was a direct plug to tap into the IF stage for this purpose. Othe radios would require some hacking to get it to work.

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Solar Safety Bag Lights Up The Night, Charges Your Phone

January 18, 2021 by Kristina Panos 15 Comments

Spend enough time riding a bike, and chances are good that you’ll start carrying a few tools with you. Even if you don’t, you’re probably going to use a bag to carry something along, so why not make that bag do triple duty? This convertible backpack/tote bag can charge your phone and provide safety lighting for nighttime rides. The design lends itself nicely to turn signals, too.

This bag was designed to show off the capabilities of Loomia, a line of prototyping parts made with e-textiles and other flexible applications in mind. It can be sewn, fused, or adhered to various substrates including fabric and wood. [AmpedAtelier] is using a Beetle microcontroller to control RGB LED strips using an illuminated Loomia soft switch on the strap. The switch is wired to the microcontroller through Loomia busses running through the strap.

Although Loomia’s site has a deep dive into the capabilities of their technology, it isn’t exactly open source. If that’s what you’re after, take a look at PolySense, which uses piezoresistive dye to create textile sensors.

Retrofitting USB-C To An IPod Nano

January 18, 2021 by Danie Conradie 29 Comments

Some hacks serve a critical need, while others are just for the challenge or fun of it. We suspect the latter was the real reason [David Buchanan] converted a first generation iPod Nano from its original 30 pin connector to USB-C.

[David] bought the iPod with a dead battery, so when he opened the iPod to get the old battery out, he noticed there was enough space to fit a USB-C connector. The original Apple 30 pin connector runs USB 2.0 through four of the pins, so [David] used the original USB cable and identified the appropriate pins and traces with a continuity tester. The connector was destructively removed with side cutters, ripping off all but one of the pads in the process. A hot air station might have made things easier, but we assume he did not have one on hand. The USB-C connector was scavenged from a cheap USC-C to USB Micro adaptor and mounted by soldering the housing directly to the PCB’s ground plane. The three remaining terminals were soldered to the traces with enamel wire.

With the new battery installed, [David] confirmed that both charging and data transfer worked. The IC that handles the button and scroll pad interfered slightly with the new connector, so he filed away some of the IC’s excess. Any open pads close to the new connector was covered with Kapton tape to avoid shorts. The large hole in the enclosure for the 30 pin connection was partly filled in with five-minute epoxy. The final assembled product looks almost factory produced and works as it’s supposed to, so we call this a win.

Retrofitting USB-C connectors in various electronic devices has become a popular hack over the past two years. We’ve seen it done on everything from Thinkpads to soldering irons. Continue reading “Retrofitting USB-C To An IPod Nano” →