software-defined radio

125 Articles

Software Defined Radio Academy Goes Virtual

July 8, 2020 by 4 Comments

They say every cloud has a silver lining. It’s hard to find a positive among all the bad news about the current global pandemic, but it has pushed more conferences and events to allow online participation either live or after the fact. A case in point: The Software Defined Radio Academy’s annual event is all on a YouTube channel so you can attend virtually.

Not all the videos are there yet, but the keynote along with some very technical talks about techniques ranging from FPGAs to spectrum monitoring and spectral correlation density — you can see that video, below. We presume you’ll eventually be able to watch all the presentations listed in the program.

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Tackling Trunked Radio With Software

June 16, 2020 by 12 Comments

For those starting to wade into radio as a hobby, one of the first real technical challenges is understanding trunked radio systems. On the surface, it seems straightforward: A control channel allows users to share a section of bandwidth rather than take up one complete channel, allowing for greater usage of the frequency range. In practice though it can be difficult to follow along, but now it’s slightly easier thanks to software defined radio.

This guide comes to us from [AndrewNohawk], who is located in San Francisco and is using his system to monitor police, fire, and EMS activity. These groups typically used trunked radio systems due to the large number of users. For listening in, nothing more than an RTL-SDR setup is needed, and the guide walks us through using this setup to find the control channels, the center frequency, and then identifying the “talk groups” for whichever organization you want to listen in on.

The guide goes into great detail, including lists of software needed to get a system like this started up, and since [AndrewNohawk] is a self-identified “radio noob” the guide is perfectly accessible to people who are new to radio and specifically new to trunked systems like these. Once you get the hang of it, it’s not too hard to scale up, either.

Receive Analog Video Radio Signals From Scratch

May 31, 2020 by 6 Comments

If you’ve been on the RTL-SDR forums lately you may have seen that a lot of work has been going into the DragonOS software. This is a software-defined radio group that has seen a lot of effort put into a purpose-built Debian-based Linux distribution that can do a lot of SDR out of the box. The latest and most exciting project coming from them involves a method for using the software to receive and demodulate analog video.

[Aaron]’s video (linked below) demonstrates using a particular piece of software called SigDigger to analyze an incoming analog video stream from a drone using a HackRF. (Of course any incoming analog signal could be used, it doesn’t need to be a drone.) The software shows the various active frequency ranges, allows a user to narrow in on one and then start demodulating it. While it has to be dialed in just right to get anything that doesn’t look like snow, [Aaron] is able to get recognizable results in just a few minutes.

Getting something like this to work completely in software is an impressive feat, especially considering that all of the software used here is free. Granted, this wouldn’t be as easy for a digital signal like most TV stations broadcast, but there’s still a lot of fun to be had. In case you missed the release of DragonOS, we covered it a few weeks ago and it’s only gotten better since then, with this project just as one example.

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Pluto Might Not Be A Planet, But It Is An SDR Transceiver

April 14, 2020 by 17 Comments

Many of the SDR projects we see use a cheap USB dongle. They are great, but sometimes you want more and — especially — sometimes you want to transmit. The Analog Devices ADALM-Pluto SDR is easily available for $200 and sometimes as low as $100 and it both transmits and receives using an Analog AD9363 and a Zynq FPGA. Although you normally use the device to pipe IQ signals to a host computer, you can run SDR applications on the device itself. That requires you to dig into the Zynq tools, which is fun but a topic for another time. In this post, I’m going to show you how you can use GNU Radio to make a simple Morse code beacon in the 2m ham band.

I’ve had one on my bench for quite a while and I’ve played with it a bit. There are several ways to use it with GNU Radio and it seems to work very well. You have to hack it to get the frequency range down a bit. Sure, it might not be “to spec” once you broaden the frequency range, but it seems to work fine. Instead of working from 325 MHz to 3,800 MHz with a 20 MHz bandwidth, the hacked device transceives 70 MHz to 6,000 MHz with 56 MHz bandwidth. It is a simple hack you only have to do once. It tells the device that it has a slightly better chip onboard and our guess is the chips are the same but sorted by performance. So while the specs might be a little off, you probably won’t notice.

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Software-Defined Radio Made Easy

April 11, 2020 by 25 Comments

Just a few decades ago, getting into hobby radio meant lots of specialty hardware, and making changes to your setup to work on various frequencies wasn’t particularly easy. Since software-defined radio (SDR) came onto the scene in an accessible way for most of us, this barrier to entry was reduced significantly and made the process of getting on the air a lot easier. It goes without saying that it does require some software, but [Aaron]’s latest project makes even getting that software extremely simple.

What he has done is created a custom Linux distribution based on Debian, called DragonOS, with the entire suite of SDR programs needed to get up and running. Out of the box, it supports RTL-SDR, HackRF and LimeSDR packages and even includes other fun tools you’ll need like Kismet. There are several video demonstrations of his distribution, including using RTL-SDR for ADS-B reception, and also shows off several custom implementations of the OS in various scenarios on his YouTube channel. The video linked below also shows how to set up the distribution in a virtual machine, so you can run this even if you don’t have a computer to dedicate to SDR.

Getting into SDR has never been easier, and the odds of having something floating around in the junk drawer that you can use to get started are pretty high. The process is exceptionally streamlined with [Aaron]’s software suite. If you’re a little short on hardware, though, there’s no better place to get started than with the classic TV-tuner-to-SDR hack from a few years back.

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The Libre Space Foundation Reviews Software Defined Radios

April 8, 2020 by 7 Comments

If you want to go to the next level with software defined radio (SDR), there are a lot of choices. The RTL-SDR dongles are fine, but if you get serious you’ll probably want something else. How do you choose? Well, your friends at the European Space Agency Libre Space Foundation have published a paper comparing many common options. True, they are mostly looking at how the receivers work with CubeSats, but it is still a good comparison.

The devices they examine are:

  • RTS-SDR v3
  • Airspy Mini
  • SDRPlay RSPduo
  • LimeSDR Mini
  • BladeRF 2.0 Micro
  • Ettus USRP B210
  • Pluto SDR

They looked at several bands of interest, but not the HF bands — not surprising considering that some of the devices can’t even operate on HF. They did examine VHF, UHF, L band, S band, and C band performance. Some of the SDRs have transmit capabilities, and for those devices, they tested the transmit function as well as receive.

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RF Shield Turns Arduino (And PC) Into Shortwave Radio

February 14, 2020 by 10 Comments

Microcontrollers tend to consume other kinds of electronics. A project you might once have done with a 555 now probably has a cheap microcontroller in it. Music synthesizers? RC controllers? Most likely, all microcontroller-based now. We always thought RF electronics would be immune to that, but the last decade or two has proven us wrong. Software-defined radio or SDR means you get the RF signal to digital as soon as possible and do everything else in software. If you want an introduction to SDR, Elektor now has an inexpensive RF shield for the Arduino. The Si5351-based board uses that oscillator IC to shift RF signals down to audio frequencies and then makes it available to the PC to do more processing.

The board is available alone or as part of a kit that includes a book. There’s also a series of Elektor articles about it. There’s also a review video from Elektor about the board in the video, below.

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