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53 Articles

Pico-Sized Ham Radio

January 10, 2024 by 18 Comments

There are plenty of hobbies around with huge price tags, and ham radio can certainly be one of them. Experienced hams might have radios that cost thousands of dollars, with huge, steerable antennas on masts that can be similarly priced. But there’s also a side to the hobby that throws all of this out of the window in favor of the simplest, lowest-cost radios and antennas that still can get the job done. Software-defined radio (SDR) turned this practice up to 11 as well, and this radio module uses almost nothing more than a microcontroller to get on the air.

The design uses the capabilities of the Raspberry Pi Pico to handle almost all of the radio’s capabilities. The RF oscillator is driven by one of the Pico’s programmable I/O (PIO) pins, which takes some load off of the processor. For AM and SSB, where amplitude needs to be controlled as well, a PWM signal is generated on another PIO which is then mixed with the RF oscillator using an analog multiplexer. The design also includes a microphone with a preamplifier which can be fed into a third PIO; alternatively it can receive audio from a computer via the USB interface. More processor resources are needed when generating phase-modulated signals like RF, but the Pico is still quite capable of doing all of these tasks without jitter larger than a clock cycle.

Of course this only outputs a signal with a few milliwatts of power, so for making any useful radio contacts with this circuit an amplifier is almost certainly needed. With the heavy lifting done by the Pico, though, the amplifier doesn’t need to be complicated or expensive. While the design is simple and low-cost, it’s not the simplest radio possible. This transmitter sends out radio waves using only a single transistor but you will be limited to Morse code only.

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ESP32 Drives Tiny FM Radio

September 14, 2023 by 21 Comments

Even as music streaming services and podcast apps dominate most of our listening time, it’s still a great idea to keep a radio on hand, if for nothing else than in emergency situations. After all, blizzards, hurricanes, and other natural disasters can quickly take out both home and mobile Internet access. If you’d like to have an FM radio with the absolute smallest footprint, take a look at this one built around an ESP32.

While the radio uses the ESP32 as the main control board hosted by a TTGO T-Display board which adds a 1.14 inch ST7789V IPS panel, it also makes use of the TEA5767 chip for handling the FM radio signals. As [Volos Projects] has it programmed, the ESP32 stores five preset channels which can be toggled using two buttons at the bottom of the device. There’s also some circuitry to handle output to headphones or a stereo.

For making the radio even smaller, some of the audio processing could be done on the ESP32 instead, although its much simpler to take a slightly larger footprint and offload this to an audio processing chip. Since the source code for this project is open, modifications could be done including adding seek/tune functionality instead of relying only on presets. If you’re not building this for emergencies, though, and your entire area is dominated by cookie cutter corporate-owned radio stations, an ESP32 with an internet connection is great for accessing better radio stations around the world.

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Supercon 2022: Sam Mulvey Shows You How To FM Radio

December 15, 2022 by 19 Comments

Sam Mulvey built his own radio station in Tacoma, WA. Is there a better way to meld ham radio practice with a colossal number of DIY electrical and computer projects? Sam would say there isn’t one! This 45-minute talk is basically the lessons-learned review of setting up KTQA 95.3 – the radio station on the hill.

Sam starts out the talk by introducing you to LPFM. And maybe you didn’t know that there’s a special type of license issued by the US FCC allowing non-profit community radio stations up to 100 W, covering an radius of around 5 km. It’s like running a pirate radio station, but by jumping through a few legal hoops, made legal.

Trash on the Radio

Putting a radio station together on a budget requires a ton of clever choices, flexibility, and above all, luck. But if you’re willing to repair a busted CD player or turntable, scrounge up some used computers, and work on your own amplifiers, the budget doesn’t have to be the limiting factor.

Being cheap means a lot of DIY. For instance, Sam and friends made a custom console to support all the gear and hide all the wiring. Some hot tips from the physical build-out: painted cinderblocks make great studio monitor stands, and Cat-5 can carry two channels of balanced audio along with power, with sufficient isolation that it all sounds clean. Continue reading “Supercon 2022: Sam Mulvey Shows You How To FM Radio” →

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Hackaday Links: December 11, 2022

December 11, 2022 by 13 Comments

“They paved paradise and put up a parking lot.” That might be stretching things a bit, especially when the “paradise” in question is in New Jersey, but there’s a move afoot to redevelop the site of the original “Big Bang Antenna” that has some people pretty upset. Known simply as “The Horn Antenna” since it was built by Bell Labs in 1959 atop a hill in Holmdel, New Jersey, the antenna was originally designed to study long-distance microwave communications. But in 1964, Bell Labs researchers Arno Penzias and Robert Wilson accidentally discovered the microwave remnants of the Big Bang, the cosmic background radiation, using the antenna, earning it a place in scientific history. So far, the only action taken by the township committee has been to authorize a study to look into whether the site should be redeveloped. But the fact that the site is one of the highest points in Monmouth County with sweeping views of Manhattan has some people wondering what’s really on tap for the site. A petition to save the antenna currently has about 3,400 signatures, so you might want to check that out — after all, you don’t know what you’ve got ’til it’s gone.

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Generating Stereo FM Signals, Thanks To Python

October 19, 2022 by 7 Comments

A casual understanding of how AM radio works is pretty easy to come by, and standard FM is only a little more complicated. Things can go off the tracks a bit with stereo FM, though — figuring out how they squeeze two separate audio tracks onto one radio signal is a bit of a head-scratcher. In that case, wrapping your head around the concept might be helped by mocking up a stereo FM signal with an arbitrary waveform generator and a little bit of Python.

Not that [Sebastian] of Baltic Lab was unfamiliar with multiplex FM theory, mind you. As he explains it, his goal was to generate a valid stereo FM signal with a different pure tone on each channel, 700 Hz on the left and 2,200 Hz on the right. Luckily, [Sebastian] has a nice AWG, the Siglent SDG1032X, which has an Ethernet connection that can be used to control it remotely along with PyVISA, a Python package for controlling instruments using the Virtual Instrument Software Architecture protocol.

The meat of this project, and what really helps drive home the concept of putting multiple audio signals onto an FM signal, lies in the Python code that generates the component parts. [Sebastian] does a great job explaining how he programatically generates the sum and difference signals along with the 19 kHz pilot tone, and puts them all together into one waveform. The output of the program is used to generate a series of values that are sent to the arbitrary waveform generator, which outputs the desired FM signal. Looking at the output on a spectrum analyzer, the two audio tones are clearly visible, as are the attenuated pilot tone and some other spikes a little further up.

Just add an antenna to the setup and you’d have the world’s dullest FM radio station — but at least it’d be in stereo. Or if you want to check out the origin story for FM radio, we’ve got something for that too.

DIy Arduino FM radio enclosure with the lid off, showing the electronics inside

DIY Arduino Due TEA5767 FM Radio

October 8, 2022 by 10 Comments

Older hackers will remember that a crystal set radio receiver was often one of the first projects attempted.  Times have changed, but there’s still something magical about gathering invisible signals from the air and listening to the radio on a homemade receiver. [mircemk] has brought the idea right up to date by building an FM radio with an OLED display, controlled with a rotary encoder.

The design is fairly straightforward, based as it is on another project that [mircemk] found on another site, but the build looks very slick and would take pride of place on any hacker’s workbench. An Arduino Due forms the heart of the project, controlling a TEA5767 module, an SH1106 128×64 pixel OLED display and a rotary encoder. The sound signal is passed through an LM4811 headphone amplifier for private listening, and a PAM8403 Class D audio amplifier for the built-in loudspeaker. The enclosure is made from PVC panels, and accented with colored adhesive tape for style.

It’s easier than ever before to quickly put together projects like this by connecting pre-built modules and downloading code from the Internet, but that doesn’t mean it’s not a worthwhile way to improve your skills and make some useful devices like this one. There are so many resources available to us these days and standing on the shoulders of giants has always been a great way to see farther.

We’ve shown some other radio projects using Arduinos and the TEA5767 IC in the past, such as this one on a tidy custom PCB, and this one built into an old radio case.

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Pocket Radio Powered By Tiny Microcontroller

July 6, 2022 by 33 Comments

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.