Friday Hack Chat: GNU Radio

August 29, 2018 by 4 Comments

Software defined radio picked up a lot of popularity when it was discovered that cheap USB TV tuners were functional bits of hardware that could become SDRs. It’s the software that makes this possible, and when it comes to SDR software, there’s no better tool than GNU Radio. For this week’s Hack Chat we’re going to sit down with some of the people behind this awesome software tool and pick their brains.

Our guests for this week’s Hack Chat will be Derek Kozel and Nate Temple, officers of the GNU Radio project. They’re also organizers of this year’s GNU Radio Conference. Also joining in on the Hack Chat will be Martin Braun, community manager, PyBOMBS maintainer, and GNU Radio Foundation officer.

GNU Radio is perhaps the most important bit of any software defined radio toolchain. This is the software that provides signal processing blocks to implement software defined radios. GNU radio is how you take a TV tuner USB dongle and pull images from satellites. You can use it for simulation, and GNU Radio is widely used by hobbyists, academics, and by people in industry.

For this week’s Hack Chat, we’re going to be talking all about GNU Radio. What can you do with it? Was the interface really inspired by MaxMSP? All that and more in this week’s Hack Chat.

  • Various bits of hardware that make GNU Radio work
  • The core process of writing modules
  • Upcoming features of GNU Radio

You are, of course, encouraged to add your own questions to the discussion. You can do that by leaving a comment on the GNU Radio Hack Chat Event Page and we’ll put that in the queue for the Hack Chat discussion.join-hack-chat

Our Hack Chats are live community events on the Hackaday.io Hack Chat group messaging. This week is just like any other, and we’ll be gathering ’round our video terminals at noon, Pacific, on Friday, August 31st. Need a countdown timer? We should look into hosting these countdown timers on hackaday.io, actually.

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 Friday; join whenever you want and you can see what the community is talking about.

Homebrew SDR Ham Radio In 9 Parts

June 6, 2018 by 31 Comments

It used to be homebrew ham gear meant something simple. A couple of active devices that could send CW. Maybe a receiver with a VFO. But only the most advanced builders could tackle a wide range SSB transceiver. Today, that goal is still not trivial, but it is way easier due to specialty ICs, ready access to high-speed digital signal processing, and advances in software-defined radio techniques. [Charlie Morris] decided to build an SSB rig that incorporated these technologies and he shared the whole process from design to operation in a series of nine videos. You can see the first one below.

The NE612 is a child of the popular NE602 chip, which contains a Gilbert-cell mixer, and an oscillator that makes building a receiver much easier than it has been in the past. The chips are set up as direct conversion receivers and feed a Teensy which does the digital signal processing on the recovered audio.

Continue reading “Homebrew SDR Ham Radio In 9 Parts” →

Software Defined Television On An ESP32

February 22, 2018 by 24 Comments

Composite video from a single-board computer? Big deal — every generation of Raspberry Pi has had some way of getting composite signals out and onto the retro monitor of your choice. But composite video from an ESP32? That’s a thing now too.

There are some limitations, of course, not least of which is finding a monitor that can accept a composite input, but since [bitluni]’s hack uses zero additional components, we can overlook those. It really is as simple as hooking the monitor up to pin 25 and ground because, like his recent ESP32 AM radio station, the magic is entirely in software. For video, [bitluni] again uses his I²S tweaks to push a lot of data into the DAC really fast, reproducing the sync and image signals in the 0-1 volt range of the PAL composite standard. His code also supports the NTSC standard, but alas because of frequency limitations in the hardware it’s monochrome only for both standards, at least for now. He’s also got a neat trick to improve performance by running the video signal generation and the 3D-rendering on separate cores in the ESP32. Check out the results in the video below.

It looks like the ESP32 is getting to be one of those “Is there anything it can’t do?” systems. Aside from radio and video, we’ve seen audio playback, vector graphics, and even a Basic interpreter easter egg.

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Tapping Into A Ham Radio’s Potential With SDRPlay

December 10, 2017 by 18 Comments

Software-defined radios are great tools for the amateur radio operator, allowing visualization of large swaths of spectrum and letting hams quickly home in on faint signals with the click of a mouse. High-end ham radios often have this function built in, but by tapping into the RF stage of a transceiver with an SDR, even budget-conscious hams can enjoy high-end features.

With both a rugged and reliable Yaesu FT-450D and the versatile SDRPlay in his shack, UK ham [Dave (G7IYK)] looked for the best way to link the two devices. Using two separate antennas was possible but inelegant, and switching the RF path between the two devices seemed clumsy. So he settled on tapping into the RF stage of the transceiver with a high-impedance low-noise amplifier (LNA) and feeding the output to the SDRPlay. The simple LNA was built on a milled PCB. A little sleuthing with the Yaesu manual — ham radio gear almost always includes schematics — led him to the right tap point in the RF path, just before the bandpass filter network. This lets the SDRPlay see the signal before the IF stage. He also identified likely points to source power for the LNA only when the radio is not transmitting. With the LNA inside the radio and the SDRPlay outside, he now has a waterfall display and thanks to Omni-Rig remote control software, he can tune the Yaesu at the click of a mouse.

If you need to learn more about SDRPlay, [Al Williams]’ guide to GNU Radio and SDRPlay is a great place to start.

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Radio Amateuring Like It’s 1975

December 7, 2017 by 33 Comments

It was a tweet from an online friend in the world of amateur radio, featuring a transmitter design published in Sprat, the journal of the G-QRP club for British enthusiasts of low-power radio. The transmitter was very simple, but seriously flawed: keying the power supply line would cause it to exhibit key clicks and frequency instability. It would probably have been far better leaving the oscillator connected full-time and keying the supply to the amplifier, with of course a suitable key click filter.

[M0CVO]'s Tweet that started it all
[M0CVO]’s Tweet that started it all
We’ve all probably made projects that get the job done at the expense of a bit of performance and economy, and from one angle this circuit is a fantastic example of that art. But it’s not the shortcomings of direct PSU keying a small transmitter that has brought it here, but observation instead of what it represents. Perhaps my social group of radio amateurs differs from the masses, but among them the universal lament is that there is nothing new in a simple transistor transmitter that could just as well have been published in 1977 as 2017.

To explain why this represents a problem, it’s worth giving some background. Any radio amateur will tell you that amateur radio is a wonderful and diverse pastime, in fact a multitude of pastimes rolled into one. Working DX? Got you covered. Contesting? UR 599 OM QRZ? Digital modes pushing the envelope of atmospheric propagation? Satellites? SDRs? GHz radio engineering? All these and many more can be yours for a modest fee and an examination pass. There was a time when radio was electronics, to all intents and purposes, and radio amateurs were at the vanguard of technology. And though electronics has moved on from those days of purely analogue communications and now stretches far beyond anything you’d need a licence and a callsign to investigate for yourself, there are still plenty of places in which an amateur can place themselves at the cutting edge. Software defined radio, for instance, or digital data transmission modes. With an inexpensive single board computer and a few components it is now possible to create a software-defined digital radio station with an extremely low power output, that can be copied on the other side of the world. That’s progress, it’s not so long ago that you would have required a lot of dollars and a lot of watts to do that. Continue reading “Radio Amateuring Like It’s 1975” →

Hackaday Prize Entry: Bloodhound Autonomous Radiolocation Drone

August 24, 2017 by 26 Comments

If you’re a first responder — say, searching for someone lost in the outback, or underneath an avalanche — and you’re looking for someone with a radio beacon, what’s the fastest way to find that beacon? Getting up high would be a good idea, and if you’re using radio direction finding, you’ll want to be able to cover a lot of ground quickly if only to make the triangulation a bit easier. High and fast — sounds like the perfect opportunity for a drone, right?

[Phil Handley]’s Bloodhound project is an autonomous drone that can scan a wide area, listening for emergency beacons while alerting the search and rescue personnel. His test bed tricopter uses DT750 brushless outrunners controlled by 18A Turnigy Plush ESCs and powered by a 2200mAh LiPo. A metal-gear servo works the yaw mechanism. He’s also got a Pixhawk Autopilot, a ArduPilot flight controller, a NavSpark GPS, a software defined radio dongle, and a Raspberry Pi. He made the air frame out of wooden dowels, following RCExplorer’s tricopter design.

The next challenge involves radio direction finding, essentially creating Bloodhound’s foxhunting skills. It needs to be able to autonomously track down a signal by taking readings from multiple angles. In addition to finding lost skiers, [Phil] also envisioned Bloodhound being used to track other beacons, of course—such as wildlife transponders or errant amateur rockets.

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Radio MDZhB

August 12, 2017 by 27 Comments

If you have a shortwave receiver, tune it to 4625 kHz. You’ll hear something that on the surface sounds strange, but the reality is even stranger still. According to the BBC, the radio station broadcasts from two locations inside Russia — and has since 1982 — but no one claims ownership of the station, known as MDZhB. According to the BBC:

[For 35 years, MDZhB] has been broadcasting a dull, monotonous tone. Every few seconds it’s joined by a second sound, like some ghostly ship sounding its foghorn. Then the drone continues.
Once or twice a week, a man or woman will read out some words in Russian, such as “dinghy” or “farming specialist”. And that’s it.

If you don’t have a shortwave handy, you can always try one of the many web-based software defined radios. Search for 4.6 MHz, and pick a location that should have propagation to Russia and you are all set.

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