Working Software-defined Radio With A TV Tuner Card.

March 30, 2012 by 77 Comments

[Balint Seeber] just sent in a small yet timely project he’s been working on: a software radio source block for the Realtek RTL2832U. Now with a cheap USB TV tuner card, you can jump right into the world of software-defined radio.

[Balint]’s code comes just a week after hackaday and other outlets posted stories about using a $20 USB TV capture dongle for software defined radio. At the time, these capture cards could only write data directly to a file. With [Balint]’s work, anyone can use a cheap tv tuner dongle with HDSDR, Winrad, or GNU Radio. If you’ve ever thought about trying out software-defined radio, now might be the time.

Elsewhere on the Internet, a surprisingly active RTL-SDR subreddit popped up dedicated to using the Realtek RTL2832U tuner for software defined radio. There’s an awesome compatibility chart listing compatible USB dongles. The cheapest (so far, and subject to change) is the Unikoo UK001T available for $11 on eBay.

With his source block, [Balint] can listen to anything on the radio between 64-1700 MHz. The sample depth is 8 bits and the sample rate can be anything up to 3.2 MHz. You can watch [Balint] testing out his $20 GNU Radio rig after the break.

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Scratch-built Software-Defined Radio

December 21, 2011 by 11 Comments

[Ben] is showing off some results from his Software-Define Radio project. The board seen above, which he designed from the ground up, is receiving a WWV radio broadcast. This is the atomic clock signal from Fort Collins, Colorado. The audio heard in the clip after the break is a bit noisy, but since he’s about 2000 miles from the origin of the signal we think he’s done really well!

The seed for this build was planted in [Ben’s] head back in July when he saw [Jeri Ellsworth’s] SDR project. He’s posted some of the build details up in a forum post. The approach is similar to [Jeri’s] but there are several key differences. He’s using a DS1085 programmable oscillator where she chose an FPGA for that purpose. Once his hardware demodulates and filters the incoming signal, a PIC32 does the rest of the work and outputs a PWM signal to an Op-Amp to generate audio.

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Retrotechtacular: 1970s Radio

June 21, 2025 by 10 Comments

Before YouTube, you had to watch your educational videos on film. In the 1970s, if you studied radio, you might have seen the video from Universal Education and Visual Arts, titled Understanding Electronics Basic Radio Circuitry. The video’s been restored, and it appears on the [CHAP] YouTube channel.

The video starts with a good history lesson that even covers Fessenden, which you rarely hear about. The video is full of old components that you may or may not remember, depending on your age. There’s a classic crystal radio at the start and it quickly moves to active receivers. There’s probably nothing in here you don’t already know. On the other hand, radios work about the same today as they did in the 1970s, unless you count software-defined varieties.

We expect this was produced for the “trade school” market or, maybe, a super advanced high school shop class. There were more in the series, apparently, including ones on vacuum tubes, the transistor, and the principles of television.

We were sad that the credits don’t mention the narrator. He sounded familiar. Maybe Robert Vaughn? Maybe not. A little research indicates the company was a division of Universal Studios, although the Library of Congress says it was actually produced by  Moreland-Latchford Productions in Toronto.

Maybe these videos were the next step in becoming a child radio engineer. If you like old radio videos, this one is even older.

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Supercon 2024: How To Track Down Radio Transmissions

June 3, 2025 by 10 Comments

You turn the dial on your radio, and hear a powerful source of interference crackle in over the baseline noise. You’re interested as to where it might be coming from. You’re receiving it well, and the signal strength is strong, but is that because it’s close or just particularly powerful? What could it be? How would you even go about tracking it down?

When it comes to hunting down radio transmissions, Justin McAllister and Nick Foster have a great deal of experience in this regard. They came down to the 2024 Hackaday Superconference to show us how it’s done.

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All-Band Receiver Lets You Listen To All The Radio At Once

January 9, 2025 by 52 Comments

There are many ways to build a radio receiver, but most have a few things in common, such as oscillators, tuned circuits, detectors, mixers, and amplifiers. Put those together in the right order and you’ve got a receiver ready to tune in whatever you want to listen to. But if you don’t really care about tuning and want to hear everything all at once, that greatly simplifies the job and leaves you with something like this homebrew all-band receiver.

Granted, dispensing with everything but a detector and an audio amplifier will seriously limit any receiver’s capabilities. But that wasn’t really a design concern for [Ido Roseman], who was in search of a simple and unobtrusive way to monitor air traffic control conversations while flying. True, there are commercially available radios that tune the aviation bands, and there are plenty of software-defined radio (SDR) options, but air travel authorities and fellow travelers alike may take a dim view of an antenna sticking out of a pocket.

So [Ido] did a little digging and found a dead-simple circuit that can receive signals from the medium-wave bands up into the VHF range without regard for modulation. The basic circuit is a Schottky diode detector between an antenna and a high-gain audio amplifier driving high-impedance headphones; [Ido] built a variation that also has an LM386 amplifier stage to allow the use of regular earbuds, which along with a simple 3D-printed case aids in the receiver’s stealth.

With only a short piece of wire as an antenna, reception is limited to nearby powerful transmitters, but that makes it suitable for getting at least the pilot side of ATC conversations. It works surprisingly well — [Ido] included a few clips that are perfectly understandable, even if the receiver also captured things like cell phones chirping and what sounds like random sferics. It seems like a fun circuit to play with, although with our luck we’d probably not try to take it on a plane.

Subchannel Stations: The Radio Broadcasts You Didn’t Know Were There

December 20, 2024 by 31 Comments

Analog radio broadcasts are pretty simple, right? Tune into a given frequency on the AM or FM bands, and what you hear is what you get. Or at least, that used to be the way, before smart engineers started figuring out all kinds of sneaky ways for extra signals to hop on to mainstream broadcasts.

Subcarrier radio once felt like the secret backchannel of the airwaves. Long before Wi-Fi, streaming, and digital multiplexing, these hidden signals beamed anything from elevator music and stock tickers to specialized content for medical professionals. Tuning into your favorite FM stations, you’d never notice them—unless you had the right hardware and a bit of know-how.

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Ham Radio In The Internet Age

October 25, 2024 by 66 Comments

Even if you are relatively young, you can probably think back on what TV was like when you were a kid and then realize that TV today is completely different. Most people watch on-demand. Saturday morning cartoons are gone, and high-definition digital signals are the norm. Many of those changes are a direct result of the Internet, which, of course, changed just about everything. Ham radio is no different. The ham radio of today has only a hazy resemblance to the ham radio of the past. I should know. I’ve been a ham for 47 years.

You know the meme about “what people think I do?” You could easily do that for ham radio operators. (Oh wait, of course, someone has done it.) The perception that hams are using antique equipment and talking about their health problems all day is a stereotype. There are many hams, and while some of them use old gear and some of them might be a little obsessed with their doctor visits, that’s true for any group. It turns out there is no “typical” ham, but modern tech, globalization, and the Internet have all changed the hobby no matter what part of it you enjoy.

Radios

One of the biggest changes in the hobby has been in the radio end. Hams tend to use two kinds of gear: HF and VHF/UHF (that’s high frequency, very high frequency, and ultra-high frequency). HF gear is made to talk over long distances, while VHF/UHF gear is for talking around town. It used to be that a new radio was a luxury that many hams couldn’t afford. You made do with surplus gear or used equipment.

Globalization has made radios much less expensive, while technological advances have made them vastly more capable. It wasn’t long ago that a handy-talkie (what normal folks would call a walkie-talkie) would be a large purchase and not have many features. Import radios are now sophisticated, often using SDR technology, and so cheap that they are practically disposable. They are so cheap now that many hams have multiples that they issue to other hams during public service events.

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