Have you dipped your toe into the SDR ocean? While hacker software-defined radio has been a hot topic for years now, it can be a little daunting to try it out for the first time. Here’s your change to get your legs under you with the SDR overview workshop presented by Josh Conway during the 2020 Hackaday Remoticon.
Josh’s presentation starts with a straightforward definition of SDR before moving to an overview of the hardware and software that’s out there. Hardware designs for radios can be quite simple to build, but they’ll be limited to a single protocol — for instance, an FM radio can’t listen in on 433 Mhz wireless doorbell. SDR breaks out of that by moving to a piece of radio hardware that can be reconfigured to work with protocols merely by making changes to the software that controls it. This makes the radio hardware more expensive, but also means you can listen (and sometimes transmit) to a wide range of devices like that wireless doorbell or automotive tire pressure sensors, but also radio-based infrastructure like airplane transponders and weather satellites.
This is the quickstart you want since it explains a lot of topis at just the right depth. The hardware overview covers RTL-SDR, ADALM-PLUTO, HackRF, KerberosSDR, and BladeRF (which we just featured over the weekend used on the WiFi procotol). For software, Josh recaps GQRX, SDR#, SDRAngel, ShinySDR, Universal Radio Hacker, Inspectrum, SigDigger, RPITX, GnuRadio Companion, and REDHAWK. He also takes us through a wide swath of the antenna types that are out there before turning to questions from the workshop attendees.
If SDR is still absent in your toolbox, now’s a great time to give it another look. Once you’ve made it through the ‘hello world’ stage, there’s plenty to explore like those awesome RF Emissions testing tricks we as in another Remoticon talk.
“Have you dipped your toe into the SDR ocean?”
Yup, it’s full of plastics. Seriously need a better indoor antenna.
band-stop filter 80MHz to 110MHz, and you may find issues with wide-band receivers less annoying. The Commercial/Music FM Radio rp-sma style kit filters are around $10 off the auction sites. YMMV, but they tend improve most SDR device receiver performance.
OpenCPN has a FOSS rtl-sdr plugin for parsing ship AIS packets, but tuning the device is tricky. I can confirm it works, and the legay PI3 OS image uses “kalibrate” to listen for the nearest cell tower band to calculate the rtl-sdr xtal ppm drift error compensation.
;-)
This is the only Remoticon video I’ve listened to (so far).
It is a good primer in my opinion.
Forty years ago when SDR was first described in hobby magazines (too early for practical projects), it wasn’t flexibility, it was better specs. By converting to digital, you could get better selectivity, and even better, a selection of bandwidths for the same price. Good receiver filters were expensive, and multiplied each time you wanted another bandwidth. That’s why receivers like the Drake R8 eventually converted to 50KHz, where LC filters were narrow enough.
When they became viable for hobbyists, the emphasis was on the digital, which was the new part. Expensive DSP boards, or using soundcards to do the conversion.
And now they are treated as black box solutions to whatever. It’s not the potential, it’s the ease. The hardware is off the shelf, as is the software.
So gone are the days of building superregens to receive that car remote, or a simple superhet to receive the police band, or that start of the art FM receiver for 2M. People get stuck in rebuilding that simple superhet from the thirties (maybe updated to solid state) instead of building something more state of the art. Fifty years ago, we had homemade radio synthesizers, frequency counters, and receivers that upconverted, but that doesn’t count.
I’m not saying SDR doesn’t count, but I think they make it easy to skip over understanding.
Or from another angle, make it easy to avoid because “they aren’t real, I can’t understand them”. but that’s just the lack of explanation.
Unless an SDR goes direct to digital, they are like parallel direct conversion receivers with digital processing. Or, a direct conversion phasing SSB receiver, with the audio phasing done in digital.
Why not build good analog receivers which then morph into digital later on? The field is wide open, not limited to black box building.
A lot of what people want to do with them is inherently digital, and it just doesn’t seem as cool to build an analog frontend to get some data that’s totally meaningless until you put it through a ton of digital processing. People used to like analog because you could do everything yourself from almost scratch.
The other thing about SDR is that they’re often used for practical purposes more than educational. They’re black boxes, but that lets you focus on your specialty, and let the analog and DSP people do theirs, because doing RF well is widely considered to be very, very hard.
band-stop filter 80MHz to 110MHz, and you may find issues with wide-band receivers less annoying. The Commercial/Music FM Radio rp-sma style kit filters are around $10 off the auction sites. YMMV, but they tend improve most SDR device receiver performance.
OpenCPN has a FOSS rtl-sdr plugin for parsing ship AIS packets, but tuning the device is tricky. I can confirm it works, and the legay PI3 OS image uses “kalibrate” to listen for the nearest cell tower band to calculate the rtl-sdr xtal ppm drift error compensation.
;-)
Mike – thank you for writing this article! I received an RTL-SDR radio and antenna kit for Christmas and have been looking for info like what you posted to help me get started. Much appreciated.
Mike – thank you for writing this article! I received an RTL-SDR radio and antenna kit for Christmas and have been looking for info like what you posted to help me get started. Much appreciated.