Retro-fit Old Radio With Arduino And FM Module

“You can’t put new wine in old bottles” – so the saying goes. But you would if you’re a hacker stuck with a radio built in 2005, which looked like it was put together using technology from 1975. [Marcus Jenkins] did just that, pulling out the innards from his old radio and converting it to an Arduino FM radio.

His cheap, mains powered radio was pretty bad at tuning. It had trouble locating stations, and tended to drift. One look at the insides, and it was obvious that it was not well engineered at all, so any attempts at fixing it would be pointless. Instead, he drew up a simple schematic that used an Arduino Nano, an FM radio module based on the TEA5767, and an audio amplifier based on the LM386.

A single button on the Arduino helps cycle through a range of preset frequencies stored in memory. The Arduino connects to the FM radio module over I2C. The existing antenna was connected to the TEA5767 module. The radio module outputs stereo audio, but [Marcus] was content with using just a mono channel, as it would be used in his workshop. The audio amplifier is pretty straightforward, based on a typical application found in the data sheet. He put it all together on proto-board, although soldering the FM radio module was a bit tricky. The Arduino code is quite simple, and available for download (zip file).

He retained the original tuning knob, which is no longer functional. The AM-FM selector knob was fitted with a micro-switch connected to the Arduino for selecting the preset stations. Almost everything inside was held together with what [Marcus] calls “hot-snot” glue. The whole exercise cost him a few Euros, and parts scavenged from his parts bin. A good radio could probably be had for a few Euros from a yard sale and much less effort, but that wouldn’t be as cool as this.

Go deeper and explore how FM signals are modulated and demodulated for playback.

30 thoughts on “Retro-fit Old Radio With Arduino And FM Module

  1. “Not well engineered” unless you count the fact they’ve probably been churning out that same PCB in millions since 1975 and it probably now costs less than the bare breadboard he shoved in there.

    Rather than throw it in the bin, I’d like to see him analyse the “crappy” radio he removed to see just how the hell they churn out a working FM radio from the cheapest stuff they can find.

    1. It looks like it’s probably just a fairly standard superheterodyne receiver made with the cheapest components they could find. I’m not surprised it drifts – these radios are tuned using a variable capacitor (the clear plastic thing with four screws in the middle) and the temperature coefficient on that is going to be awful compared to the crystal that the TEA5767 uses for its frequency reference.

  2. Am I the only one who doesn’t see anything wrong with the build construction of that radio. It doesn’t look cheap, just optimized. Its design evidently comes from a time when engineers were able to design functioning products without the need for microcontrollers.

    1. It could be stuffed a little cleaner, but otherwise it is fine. At first glance I thought it was covered in battery acid over the copper winding and ferrite core

    2. There’s nothing wrong with the technology; it’s the implementation that’s poor. Technology historian Henry Petrosky talks about the life of a technology. First, it is new and expensive; but outperforms earlier tech, and so gets used in high-end applications. Lots of effort goes into design and construction. Second, it becomes mainstream and replaces the old tech. Third, it gets cheapened, and cheapened even more, until it barely works. That creates the opportunity for it to get replaced by a still newer tech. The cycle goes on and on… relays to tubes, tubes to transistors, transistors to ICs, ICs to micros… I wonder what comes next?

  3. >which looked like it was put together using technology from 1975.

    That is a bit newer than 1975 as the AM/FM radio uses a chip for most of the IF stages already. The much older design would have used discrete transistors along with additional IF cans for AM and FM side. Those circuits are actually simple enough to be understood and appreciated by a real hacker.

    Here is a bit of irony for the write up that denounce 1975 technology.
    http://www.electrosmash.com/lm386-analysis
    >The LM386 Voltage Audio Power Amplifier by National Semiconductor and also manufactured by JRC/NJM, is an old chip (mid 70’s) that has been a popular choice for low-power audio applications.

    1. Yah project is nice but the website not so much.
      A popup saying you require cookies and then the redirect to a the definition of paranoia when you click no was pretty jerkish also modal popups that block content are a horrible thing that needs to be eliminated from the internet.
      Using them is bad and people should feel bad when they use them.

      Oh I was able to view the site without clicking yes thanks to a nice little feature in firefox.

      I think there’s a need for a plugin that automatically removes lightbox modal popups from web pages.

      1. Yeah that little spiel and redirecting you to the Wikipedia page for paranoia just made me realize the guy must be an asshole.

        Inspect element and deleting the bullshit div node lets you see the content, as meh as it was. I guess his cookie wasn’t necessary after all!

    1. I’ve always heard that saying with wineskins, not wine bottles – which might make more sense, as wine skins (cloth or leather) wear out with age. And no one wants to loose new wine when the old container breaks!

      1. I’m not trying to start a flame war, this is just an FYI

        Wineskins stretch as the wine ferments, just like homebrewers putting a balloon over their bottle. Putting new wine into an old (stretched out) wineskin would result in the skin bursting and losing the new wine.

        P.s. that verse comes from The Bible, a lot of today’s idioms come from The Bible, such a “feet of clay”. As The Bible is no longer used in U.S. public schools, unlike a 100 years ago, many people do not know where a lot of these idioms originated.

  4. Cheap!
    They leave out a whole IF stage in these junk radios. Can’t separate two stations 2 or 3 channels apart. Powerhouses bleed in allover the dial in a party of crud. It’s not drift, just walking around it shifts the strength of locals which trash it up.
    There ought to be a yellow tag program to identify all radios sold, and a performance line to show consumers what they are buying. Car radios are your best bet at good performance. They usually have the full set of IF stages and use a TRF stage as well.
    I have yet to see and hear a shootout with SDR against real radios. But a good multimode agile scanner I tried on the FM band washed out especially when hooked to a beam antenna.

    1. Yeah most scanners fare terribly on broadcast FM. One neither needs a proper monitoring or measuring receiver or a dedicated broadcast fm tuner. The FMDX crowd knows more about that. My FT-897 hamrig fails miserably on broadcast fm with weak stations, just tons of intermod and crap. but i’ts an OK radio on hambands.

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