Top DNG Builds a $600 Digital Radio Scanner on the Cheap — with a Raspberry Pi 5 and RTL-SDR

Designed as a more affordable alternative to a Uniden P25, this digital radio scanner picks up emergency traffic and more.

Gareth Halfacree
4 months agoCommunication / HW101

Pseudonymous YouTuber "Top DNG" has demonstrated how a Raspberry Pi 5 and an RTL-SDR software-defined radio dongle can be turned into a radio scanner for digital radio transmissions, including those used by emergency services — duplicating the functionality of $600 off-the-shelf hardware at a far lower cost.

"The digital P25 radio from Uniden is maybe 600 bucks," Top DNG explains, "and I don't really care to pay that much for that. So, to pick up those kind of signals on the cheap you get one of these dongles: the RTL-SDR. These are, like, 30 bucks, but of course the problem with these is they need something to plug into, and you need to run some software — it's not all contained in here, this is just the dongle."

If you're wondering what the sirens are all about, this pocket-friendly Raspberry Pi-powered radio scanner can clue you in. (📹: Top DNG)

The solution, for use on-the-go at least, is to connect the RTL-SDR dongle — a low-cost receive-only software defined radio — to a single-board computer. In Top DNG's case that's the new Raspberry Pi 5, launched late last year as the most powerful Raspberry Pi by far and easily up to the task of driving the RTL-SDR dongle and decoding the transmissions it receives.

"I know some people have tried to do this before with Raspberry Pi 4s," Top DNG explains, "and they just were not powerful enough. So with the [Raspberry Pi] 5 we're unlocking this [type of] portable scanner [functionality] on the cheap."

The Raspberry Pi 5 connects to the RTL-SDR over USB, while an HDMI touchscreen display provides a user interface. Speakers built into the monitor mean the decoded transmissions can be heard — a trickier task on the Raspberry Pi 5 than earlier models, as it's the first to drop the analog audio/video (AV) jack — and a USB Type-C power supply gets everything up and running.

"We're running the [Raspberry] Pi in headless mode and only launching the SDR software, so there's no other desktop stuff going on," Top DNG notes of the the user experience. "I've configured this thing with the LAPD [Los Angeles Police Department] channels, and I suggest doing that on your computer and just loading in the XML file which defines, basically, how this whole software operates in terms of what you're recording."

The full video is available embedded above and on Top DNG's YouTube channel.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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