Building a Magic Radio

Years ago, I had this idea for a gimmicky MP3 player. It wouldn’t have a screen or any buttons; instead, it would play music and podcasts on a pre-defined schedule. I’d build it into an antique radio so that using it might feel a little like listening to an authentic radio station.

The idea sat in the back of my mind for many years. The challenge was a bit outside my comfort zone, so I generally worked on more familiar projects. Then the year 2020 arrived. The more fortunate among us found ourselves with a bunch of unexpected free time. I spent mine building the Magic Radio.

Demonstration

The user interface is intentionally minimal: you turn on the radio and tune to 87.5 FM. You hear whatever’s scheduled for that moment.

The playback schedule (along with all the audio files) is stored on a USB storage device that’s plugged in to a panel on the back. End users can yank that out, plug it in to a laptop, and reprogram the “station” with their own audio files and schedule. They can also configure the broadcasting frequency to accommodate the authentic stations in their area.

The configuration is a YAML-formatted text file. The system provides instructions on how to edit the configuration by saving documentation (another text file, this one with plain English prose) to the storage device whenever it’s plugged in. The system also writes a log file on there so users can review a journal of its behavior and learn about any run-time errors it encountered.

My goal was to empower a non-programmer to operate the radio. While this solution requires a fair amount of technical fluency, I’m reasonably satisfied with the result, given the constraints.¹

Why would anyone enjoy this?

An honest pitch for this device might go, “It’s like an MP3 player, but worse!” It’s not for everyone. And honestly, even if you dig the concept, it may not be that interesting to own. This is the most subtle quality that it shares with traditional radio: a lot of the “magic” comes from the value of curation. There’s not much room for serendipity in a device that you’ve constructed and programmed to behave according to your specifications.

The Magic Radio works best as a gift. If you know someone who would appreciate the aesthetic, then it makes for an excellent canvas. You can really layer in a lot of thoughtful content, and your curation will be more meaningful than the physical device.

For instance: I gave this to a neighbor who used to love Boston’s defunct alternative rock station, WFNX. For a few hours every Saturday, it plays 90’s rock and intersperses old WFNX station identifiers.

Lessons Learned

Like any good personal project, building this device taught me new things and reinforced other stuff I only thought I knew.

Don’t optimize early. “This thing has a simple job, so it should be built with simple hardware.” At least, that’s how I was thinking when I started. I wanted to use a prototyping board, but not to save money or power; I set that goal just on principle. Red flag, there. I wasted a lot of time trying to decide which of the many, many such boards would be suitable. Eventually, I had to admit that I lacked the experience to make the right call, so I bought a general-purpose computer–the Raspberry Pi. Even though I told myself that I’d eventually replace it with a leaner component, it quickly became clear that this was a good move. The availability of a high-level scripting language (i.e. Python) let me experiment with new ideas very quickly, and access to the entire ecosystem of GNU/Linux utilities (e.g. systemd) saved me from writing my own hacky solutions to well-understood problems.

And when I did indulge my inclination toward optimization, I sometimes regretted it. I didn’t want the Raspberry Pi floating around inside the radio, risking short circuits and other tomfoolery; I needed some kind of enclosure. I bought this really slick case thinking it would solve my problem. Unfortunately, it turned out that the other components (the FM transmitter and the hardware clock) wouldn’t fit inside. The package it came in, on the other hand…

$15 is a hefty price tag for a cardboard box, but I’ve made worse purchases.

Prototypes can be inspiring. After years of thinking about this, I assumed I had a pretty good handle on what I was going to build. It wasn’t until I started actively working on it–buying components, writing code, and testing subsystems–that I started to get brand new ideas.

For instance, I originally planned to use the radio as a fancy enclosure, gutting it and installing a new set of speakers wired directly to the computer inside. It wasn’t until after I’d purchased the radio that I realized how integrating an FM transmitter would be worlds better. That provides a much more authentic user experience, from the physical interaction of tuning to the degraded audio quality (because people need to hear snaps and pops and that shit). It also preserves the device’s ability to play local radio stations. And it also means users can tune to the “magic” station using any other radio they have in range.

Later on, when I heard the end of a day’s programming schedule, I recognized how abrupt that can feel. From the early days of terrestrial radio, broadcasters prepared listeners for that lonely silence with “station sign off” messages. I listened to a handful from the 1950’s (e.g. these beauties from Cleveland) and recorded one of my own.

archive.org is amazing. From original broadcasts of MLB World Series games to old-timey radio series like Gunsmoke and Boston Blackie, archive.org is full of fascinating and free vintage media. I filled most of the weekly schedule with content hosted there, almost 64 gigabytes of audio, all told. It won’t play a repeat for years.

Adafruit is amazing. Adafruit provided all of the hardware for this project. It’s a 100% woman-owned manufacturing company, a certified Minority and Woman-owned Business Enterprise (M/WBE), a certified Women’s Business Enterprise (WBE), and WOSB. And, amazingly for an electronics manufacturer in this day and age, it’s based in the US. If that was all there was to say about the company, I would be a huge fan. But as you’d expect from a pedigree like that, the company’s products and services are phenomenal.

Adafruit provides approachable and in-depth documentation for everything it produces. They offer tutorials written to nurture interest in technology and empower newcomers, especially those from groups who are historically under-represented in the tech industry. By giving them your business, you can’t help but feel like you’re contributing (however minimally) to a good cause. And since I don’t build many hardware projects, that content gave me the confidence I needed to finally give this a shot.

shopgoodwill.com is amazing. From Goodwill’s page on Wikipedia:

Goodwill is an American nonprofit 501(c)(3) organization that provides job training, employment placement services, and other community-based programs for people who have barriers preventing them from otherwise obtaining a job. Additionally, Goodwill Industries may hire veterans and individuals who lack education or job experience or face employment challenges. Goodwill is funded by a massive network of retail thrift stores which operate as nonprofits as well.

Those are all great reasons to support your local store, if you’re lucky enough to live near one. Unfortunately, as a thrift store, the inventory is pretty hit-or-miss. While considering other retailers for a vintage radio, I was psyched to discover that Goodwill operates an online auction site from the inventory of its stores around the US. I had my pick of affordable pre-owned radios, with new choices popping up almost daily. That site is my new go-to for basic household equipment.

By the way: It’s easy to get excited about a new hardware project, but it’s also important to have a plan for its end of life. Goodwill partners with Dell to offer responsible electronics recycling. Don’t toss those old components in the garbage!

Functional testing is critical for physical projects. Most of my personal projects are based entirely in software. I unit tested the crap out of my code, naturally, but the real world is a messy place. Building the Magic Radio helped me appreciate how a physical deployment with actual data is full of unknown unknowns.

For instance, the Raspberry Pi lacks an internal clock, but I only discovered this after running a week-long trial. One day, I happened to be futzing with my home’s fuze box. I temporarily cut power to a circuit which included the device so I could install a light fixture nearby. Later that day, right around the time that The Shadow was due to air, the radio was silent. It turned out that the computer’s clock was half an hour late thanks to the time it spent powered down. This didn’t occur to me throughout all of development because the device constantly synchronized with network time while it was connected to my laptop. The Raspberry Pi and Adafruit came through again, enabling me to buy a component and plug it in, almost as intuitively as playing with Legos. It would have been much more of a hassle to diagnose and fix this after giving the radio as a gift.

Or there was the time the radio went silent after playing an episode of Our Miss Brooks. It was supposed to play some old advertisements, though! It turned out that about 1% of the audio files had faulty metadata. My code assumed the metadata was infallible, and as a result, the system would refuse to queue new files even though nothing was actually playing; it was waiting for the show to end. The fix was to measure the true duration of audio files by decoding them (an expensive operation, but one that could be optimized through aggressive caching). I never would have caught this if I hadn’t tried running the system for a while (and even then, it’s pretty fortunate that I stumbled on one of the few outliers).

Nostalgia is powerful stuff. This project is pretty sentimental. Maybe that goes without saying, but I was still surprised at the emotional effect it had on me–especially considering the years I’d spent thinking about it. Old time radio, though occasionally marred by sexist or racist themes, is otherwise more charming than I first realized. Music from my childhood, punctuated by echos of a long-lost radio station, was even more powerful. It’s given me a better appreciation of how friction can enhance an interaction. Playing a vinyl record takes more attention and effort than tapping on an MP3 file, and that makes you a little more invested. I think the same can be said for the sounds coming out of this radio: if you don’t pay attention, then you’re out of luck. Knowing that seems to matter on some subconscious level.

“Wishing you all a good night and a pleasant good morning”

The Magic Radio was tons of fun to build and especially satisfying given how long it’s sat in the back of my mind. It happens to be the third pet project I’ve completed using the time I would otherwise have spent in public and interacting with people (first was a silly cooking tool, next came a bizarre software legal fight). I’m grateful for the health and financial security I’ve needed to do this, but I’ll be glad when spare time is a little harder to come by again.

If you’d like to build something similar for yourself, then check out the source code (it includes some tips for getting started), and don’t hesitate to contact me with questions!