Before the days of MP3 players and smartphones, and even before portable CD players, those of us of a certain age remember that our cassette players were about the only way to take music on-the-go. If we were lucky, they also had a built-in radio for when the single tape exhausted both of its sides. Compared to then, it’s much easier to build a portable radio even though cassettes are largely forgotten, as [wagiminator] shows us with this radio design based on an ATtiny.
The build is about as compact as possible, with the aforementioned ATtiny 402/412 as its core, it also makes use of an integrated circuit FM tuner, an integrated audio amplifier with its own single speaker, and a small OLED display. The unit also boasts its own lithium-polymer battery charger and its user interface consists of only three buttons, plenty for browsing radio stations and controlling volume.
The entire build fits easily in the palm of a hand and is quite capable for a mobile radio, plus all of the schematics and code is available on the project page. While it doesn’t include AM capability, just the fact that FM is this accessible nowadays when a few decades ago it was cutting-edge technology is quite remarkable. If you’re looking for an even smaller FM receiver without some of the bells and whistles of this one, take a look at this project too.
When you think old school handheld games, you probably imagine something like Nintendo’s Game Boy line or the Sega Game Gear. But outside of those now iconic systems, there was a vast subculture of oddball handheld games vying for a chunk of an adolescent’s weekly allowance. Many of these were legitimately terrible and frankly aren’t worth remembering, but a few offered unique features that were arguably ahead of their time.
One such game was Hasbro’s short-lived P-O-X. As explained by [Zachary Ennenga], the game didn’t spend much time on store shelves as its core concept of defeating undetectable alien invaders hell-bent on destroying our way of life proved to be more than a little problematic when it launched in September of 2001. But that doesn’t mean it didn’t have some cool ideas, such as a wireless ad-hoc multiplayer capability that let your game autonomously battle it out with other units that got close by.
Fascinated by this feature since his youth, [Zach] set out to study how this relatively cheap kid’s toy was able to pull this off back when even the flagship handheld consoles were still using physical link cables for multiplayer. He was aided in his quest by a particularly helpful patent, which not only gave him clues as to the frequency, data rate, modulation, and encoding of the RF signal, but even explained the game’s logic and overall structure. A lot of what was in the document seemed wishful thinking on the part of Hasbro, but reading through the marketing speak still uncovered some salient technical details.
A decoded P-O-X packet.
Armed with an RTL-SDR, GNU Radio, Inspectrum, and a bit of Python, [Zach] was able to identify the signal and begin the process of decoding it. This is where things get really interesting, as the details of his reverse engineering process are widely applicable for all sorts of unknown RF signals. Even if you’re like most people and have nearly zero interest in failed handheld games of the early 2000s, it’s well worth a read. The same techniques he uses to figure out the name and physical characteristics of the invisible foe his game is transmitting could one day help you figure out how to manipulate the data from that wireless weather station you’ve got in the backyard.
Once he figured out the major parts of the protocol, [Zach] moves on to creating his own packets and broadcasting them out in such a way that the real hardware will recognize it. He even comes up with some code that will automatically battle games which wander within range of his Yardstick One, which may come in handy during the inevitable P-O-X Renaissance.
While this might seem like a lot of effort to put into a game that most people have never even heard of, we’ll remind you that some of the greatest hacks to ever grace these pages have been born of similar pursuits. Even if you’re the only person in the world to directly benefit from your current line of research and experimentation, there’s still plenty of like-minded folks in this community that are all to happy to cheer you on from the sidelines.
[David], DL1DN, is an Amateur Radio enthusiast with a penchant for low-power (QRP) portable operations. Recently he was out and about, and found that 10 m propagation was wide open. Not discouraged by having forgotten his antenna, he kludges up a makeshift one using a 20 cm length of aluminum foil (see video demonstration below the break). [David] wasn’t completely unprepared, as he did have the loading coil for his portable 20 m antenna, but was missing the telescoping whip. He calculated the whip length should be around 20 cm for 10 m operation, and crinkles up a sheet of foil the approximate length. He tunes it to length by rolling the tip to shorten the “whip” until he gets an SWR minimum.
Schematic of [David]’s QRP Portable Whip Antenna[David] describes this style of portable antenna in another video, using a more conventional telescoping whip as the radiating element. The loading coil is built from common PVC pipe and insulated wire. While these aren’t necessarily the most efficient antennas, they can do the trick when portability is a major concern. For a different approach, here’s a QRP Hackaday.io portable antenna project using a magnetic loop antenna. But for the ultimate in QRP, check out this transmitter we wrote about in 2013 that uses only voice power to operate.
What are some unusual items you’ve used as makeshift antennas? Let us know in the comments below. Thanks to [mister35mm] for submitting this to our tip line.
A metrology geek will go to extreme lengths to ensure that their measurements are the best, their instruments the most accurate, and their calibration spot-on. There was a time when for time-and-frequency geeks this would have been a difficult job, but with the advent of GPS satellites overhead carrying super-accurate atomic clocks it’s surprisingly easy to be right on-frequency. [Land-boards] have a GPS 10 MHz clock that’s based around a set of modules.
Since many GPS modules have a 10 MHz output one might expect that this one to simply hook a socket to the module and have done, but instead it uses another of their projects, a fast edge pulse generator with the GPS output as its oscillator, as a buffer and signal conditioner. Add to that an QT Py microcontroller board to set up the GPS, and there you have a standalone 10 MHz source to rival any standard. Full details can be found on the project’s wiki, and the firmware can be found on GitHub.
Even though not every Hackaday reader is likely to be a radio enthusiast, it’s a fair guess that many of you will have experimented with an RTL-SDR USB dongle by now. These super-cheap devices are intended for digital TV reception and contain an RTL2832 chip, which with the proper software, can be pushed into service as a general purpose software defined radio receiver. For around $10 USD they’re fantastic value and a lot of fun to play with, even if they’re not the best radio ever. How to improve the lackluster performance? One of the easiest and cheapest ways is simply to shield it from RF noise, which [Alan R] has done with something as mundane as a tubular fizzy orange tablet container.
This is probably one of the simpler hacks you’ll see on this site, as all it involves is making an appropriate hole in the end of the tube and shielding the whole with some aluminium foil sticky tape. But the benefits can be seen immediately in the form of reduced FM broadcast band interference, something that plagues the cheaper dongles.
Perhaps the value in this hack aside from how easy it is on a cheap dongle is that it serves to remind us some of the benefits of paying a little extra for a better quality device. If you’d like to know more about RTL-SDR improvements, it’s a topic we covered in detail back in 2019 when we looked at seven years of RTL-hackery.
With music consumption having long ago moved to a streaming model in many parts of the world, it sometimes feels as though, just like the rotary telephone dial, kids might not even know what a radio was, let alone own one. But there was a time when broadcasting pop music over the airwaves was a deeply subversive activity for Europeans at least, as the lumbering state monopoly broadcasters were challenged by illegal pirate stations carrying the cutting edge music they had failed to provide. [Ringway Manchester] has the story of one such pirate station which broadcast across the city for a few years in the 1970s, and it’s a fascinating tale indeed.
It takes the form of a series of six videos, the first of which we’ve embedded below the break. The next installment is placed as an embedded link at the end of each video, and it’s worth sitting down for the full set.
It’s fair to say that right now is probably the worst possible time you could choose to design a new piece of hardware. Of course the reality is that, even in the middle of a parts shortage that’s driving the cost of many components through the roof (if you can even find them), we can’t just stop building new devices. In practice, that means you’ll need to be a bit more flexible when embarking on a new design — it’s like the Stones said: “You can’t always get what you want / But if you try sometime you’ll find / You get what you need”
