Multi-Band Receiver On A Chip Controlled By Arduino

March 2, 2020 by Tom Nardi 18 Comments

The Silicon Labs Si4735 is a single-chip solution for receiving AM, FM, and shortwave radio. With a bit of hacking, it even supports single sideband (SSB). All you’ve got to do is provide it with a suitable control interface, which [Ricardo Lima Caratti] has done with his recent project.

Using an Arduino Pro Mini, a handful of buttons, and a standard TFT display, [Ricardo] has put together a serviceable little receiver with a fairly impressive user interface. We especially like the horizontal bars indicating the signal to noise ratio and received signal strength. The next evolution would be to put this whole rig into some kind of enclosure, but for now he seems content to control the action with a handful of unlabeled buttons on a piece of perfboard.

Of course, the presentation of this receiver isn’t really the point; it’s more of a proof of concept. You see, [Ricardo] is the person who’s actually developed the library that allows you to control the Si4735 from your microcontroller of choice over I2C. He’s currently tested it with several members of the official (and not so official) Arduino family, as well as the ESP32.

The documentation [Ricardo] has put together for his MIT licensed Arduino Si4735 library is nothing short of phenomenal. Seriously, if all open source projects were documented even half as well as this one is, we’d all be a few notches closer to world peace. Even if you aren’t terribly interested in adding shortwave radio reception to your next project, you’ve got to browse his documentation just to see where the high water mark is.

We actually first heard about this library a few days ago when we covered another receiver using the Si4735 and [Ricardo] popped into the comments to share some of the work he’d been doing to push the state-of-the-art forward for this promising chip.

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DIY Radio Telescopes Hack Chat

February 10, 2020 by Dan Maloney 8 Comments

Join us on Wednesday, February 12 at noon Pacific for the DIY Radio Telescopes Hack Chat with James Aguirre!

For most of history, astronomers were privy to the goings-on in the universe only in a very narrow slice of the electromagnetic spectrum. We had no idea that a vibrant and wondrous picture was being painted up and down the wavelengths, a portrait in radio waves of everything from nearly the moment of creation to the movement of galaxies. And all it took to listen in was an antenna and a radio receiver.

Over the years, radio telescopes have gotten more and more sophisticated and sensitive, and consequently bigger and bigger. We’re even to the point where one radio telescope often won’t cut it, and astronomers build arrays of telescopes spread over miles and miles, some with antennas that move around on rails. In the search for signals, radio astronomy has become the very definition of “Big Science.”

But radio astronomy doesn’t have to be big to be useful. James Aguirre, an astronomer at the University of Pennsylvania, spends his days (and nights) studying the radio universe with those big instruments. But he’s also passionate about down-scaling things and teaching everyone that small radio telescopes can be built on the cheap. His Mini Radio Telescope project uses a cast-off satellite TV dish and a couple of hundred bucks worth of readily available gear to scan the skies for all sorts of interesting phenomena.

Dr. Aguirre will join us on the Hack Chat to discuss all things radio astronomy, and how you can get in on the radio action on the cheap. Chances are good your junk pile — or your neighbor’s roof — has everything you need, and you might be surprised how approachable and engaging DIY radio astronomy can be.

Our Hack Chats are live community events in the Hackaday.io Hack Chat group messaging. This week we’ll be sitting down on Wednesday, February 12 at 12:00 PM Pacific time. If time zones have got you down, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on Hackaday.io. You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about. Continue reading “DIY Radio Telescopes Hack Chat” →

Clock Radio Receives Upgrade

May 5, 2019 by Bryan Cockfield 8 Comments

Before everyone had a cell phone alarm to wake them up in the mornings, most of us used clock radios that would faithfully sit by our beds for years. You could have either a blaring alarm to wake you up, or be gently roused from slumber by one of your local radio stations. These devices aren’t as commonly used anymore, so if you have one sitting in your parts drawer you can make some small changes and use it to receive radio stations from a little further away than you’d expect.

This Panasonic clock radio from [Ryan Flowers] has several upgrades compared to the old clock radio hardware. For one, it now can receive signals on the 7 and 14 MHz bands (40 and 20 meters). It does this by using separate bandpass filters for each frequency range, controlled by a QRP Labs VFO kit which can switch between the two filters automatically once programmed. The whole thing is powered by 8 AA batteries, true to form with a clock radio from the ’90s.

[Ryan] notes that his first iteration was a little quiet but he’s now able to receive radio stations from as far away from Japan with this receiver. Even without a license, you can make these changes and listen in to stations from all around the world, as long as you don’t start transmitting. If you want to make a small upgrade from this clock radio though, it’s not that hard to get into.

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Superheterodyne Radios Explained

January 2, 2019 by Al Williams 17 Comments

The general public thinks there is one thing called a radio. Sure, they know there are radios that pick up different channels, but other than that, one radio is pretty much like the other. But if you are involved in electronics, you probably know there are lots of ways a radio can work internally. A crystal set is very different from an FM stereo, and that’s different still from a communications receiver. We’d say there are several common architectures for receivers and one of the most common is the superheterodyne. But what does that mean exactly? [Technology Connection] has a casual explanation video that discusses how a superhet works and why it is important. You can see the video, below.

Engineering has always been about building on abstractions. This is especially true now when you can get an IC or module that does most of what you want it to do. But even without those, you would hardly start an electronics project by mining copper wire, refining it, and drawing your own wire. You probably don’t make many of your own resistors and capacitors, neither do you start your design at the fundamental electronic equations. But there’s one abstraction we often forget about: architecture. If you are designing a receiver, you probably don’t try to solve the problem of radio reception; instead you pick an architecture that is proven and design to that.

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Radio Gets Ridiculous

December 21, 2018 by Al Williams 16 Comments

There were plenty of great talks at this year’s Supercon, but we really liked the title of Dominic Spill’s talk: Ridiculous Radios. Let’s face it, it is one thing to make a radio or a computer or a drone the way you are supposed to. It is another thing altogether to make one out of things you shouldn’t be using. That’s [Dominic’s] approach. In a quick 30 minutes, he shows you two receivers and two transmitters. What makes them ridiculous? Consider one of the receivers. It is a software defined radio (SDR). How many bits should an SDR have? How about one bit? Ridiculous? Then you are getting the idea.

Dominic is pretty adept at taking a normal microcontroller and bending it to do strange RF things and the results are really entertaining. The breadboard SDR, for example, is a microcontroller with three components: an antenna, a diode, and a resistor. That’s it. If you missed the talk at Supercon, you can see the newly published video below, along with more highlights from Dominic’s talk.

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Cross-Correlation Makes Quick Work Of Ads

August 22, 2018 by Kerry Scharfglass 25 Comments

Once relegated to the proverbial Linux loving Firefox user, ad blocking has moved into public view among increased awareness of privacy and the mechanisms of advertising on the internet. At the annual family gathering, when That Relative asks how to setup their new laptop, we struggle through a dissertation on the value of ad blockers and convince them to install one. But what about mediums besides the internet? Decades ago Tivo gave us one button to jump through recorded TV. How about the radio? If available, satellite radio may be free of The Hated Advertisement. But terrestrial radio and online streams? [tomek] wasn’t satisfied with an otherwise sublime experience listening streaming Polish Radio Three and decided to build a desktop tool to detect and elide ads from the live audio stream.

[tomek] was aware of this hip knowledge domain called Digital Signal Processing but hadn’t done any of it themselves. Like many algorithmic problems the first step was to figure out the fastest way to bolt together a prototype to prove a given technique worked. We were as surprised as [tomek] by how simple this turned out to be. Fundamentally it required a single function – cross-correlation – to measure the similarity of two data samples (audio files in this case). And it turns out that Octave provides it in the box. After snipping the start-of-ad jingle out of a sample file and comparing it to a radio program [tomek] got the graph at the left. The conspicuous spike is the location of the jingle in the audio file.

At this point all that was left was packaging it all into a one click tool to listen to the radio without loading an entire analysis package. Conveniently Octave is open source software, so [tomek] was able to dig through its sources until they found the bones of the critical xcorr() function. [tomek] adapted their code to pour the audio into a circular buffer in order to use an existing Java FFT library, and the magic was done. Piping the stream out of ffmpeg and into the ad detector yielded events when the given ad jingle samples were detected.

[tomek] packaged that tool into a standalone executable, but the gem here is the followup post. After removing ads in the online stream they adapted a RaspberryPi to listen to an FM receiver and remote control their Yamaha tuner over the network. So when the tuner is playing Radio Three the Pi notices and ducks the audio appropriately to avoid those pesky ads. Video of this after the break.

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This Mostly 3D-Printed Discone Antenna Is Ready For Broadband Duty

May 29, 2018 by Dan Maloney 16 Comments

For hams and other radio enthusiasts, the best part of the hobby is often designing antennas. Part black magic, part hard science, and part engineering, antenna design is an art. And while the expression of that art often ends up boiling down to pieces of wire cut to the correct length, some antennas have a little more going on in the aesthetics department.

Take the discone antenna, for example. Originally designed as a broadband antenna to sprout from aircraft fuselages, the discone has found a niche with public service radio listeners. But with a disk stuck to the top of a cone, the antennas have been a little hard to homebrew, at least until [ByTechLab] released this mostly 3D-printed discone. A quick look at the finished product, resembling a sweater drying rack more than a disc on top of a cone, reveals that the two shapes can be approximated by individual elements instead of solid surfaces. This is the way most practical discones are built, and [ByTechLab]’s Thingiverse page has the files needed to print the parts needed to properly orient the elements, which are just 6-mm aluminum rods. The printed hub pieces sandwich a copper plate to tie the elements together electrically while providing a feedpoint for the antenna as well as a sturdy place to mount it outdoors. This differs quite a bit from the last 3D-printed discone we featured, which used the solid geometry and was geared more for indoor use.

Interested in other antenna designs? Who can blame you? Check out the theory behind the Yagi-Uda beam antenna, or how to turn junk into a WiFi dish antenna.

[via RTL-SDR.com]