SDR is amazing!
Here are some more things you can do with your RTL-SDR after the first 50:
Meteor weather satellite reception (Russian counterpart of the NOAA satellites, but digital, so higher res and in color)
Digital Radio Mondiale -- digital radio but for shortwave
Analog TV -- if you're in an area that still broadcasts this (unlikely), you can receive a black & white picture and closed captioning. If no OTA broadcasts remain, you can use the analog output of a VCR or DVD player
GPS -- rtlsdr is capable of decoding GPS, Galileo, and BeiDou! (Likely not GLONASS since each satellite uses a separate frequency, spreading the signal beyond the sdr's bandwidth)
Hidden secondary audio broadcasts inside FM radio (like the stereo audio hack, but using higher frequencies in the demodulated stream)
Brazilian outlaws and UHF pirates using open repeaters on US military satellites launched in the 70s
TEMPEST / "Van Eck phreaking" where you can remotely read a nearby screen due to leakage from the monitor or video cabling
Instrument landing system -- if you're near an airport you can tune to a runway's ILS frequency and see the signal change as you move from the left side of the runway to the right
Infrared remotes -- stick an IR photodiode in the antenna port and you can demodulate codes from remote controls
Passive radar -- Tune into a very narrowband signal like a VOR or ATSC pilot signal, set your decimation extremely high (i.e., trading bandwidth for dynamic range) and you can see nearby planes in the area from their doppler-shifted reflections of the main signal
A few months ago when there was a lot of emergency services activity in my area and I didn't know why, I was reminded that no-one in my region is contributing a feed to Broadcastify.
I went down the tunnel of using SDR to recieve those transmissions, and share them online.
Then I went a bit further.
What if you could transcribe the broadcasts into something like a text feed? What if you could add location information somehow to monitor where things were going on in your region? Could you use AI to somehow organize the data into a more useful format?
What if this data was valuable? Maybe you could sell this as a service? Who would buy it? Public safety organizations? Hospitals? News organizations?
I spent a few days worth of freetime figuring out how you'd do someting like this, and got to a place where I figured it was conceptually possible.
Then somewhere in my googling, I stumbled across this site: http://citizen.com/ - and realized that someone had already turned my idea into what looks like a pretty mature product.
Ahh well. I'm sure my billion dollar idea will come later.
In the meantime, I'd still like to mess with SDR at least so I can know what's going on around me next time there's a fire or other public safety incident, before it gets reported on.
Sadly, you can't really get NOAA satellite images any more. NOAA-15 and 19 were decommissioned August 19, 2025, and NOAA 18 was decommissioned in June. It's my understanding that you'll need a much more powerful antenna to get images from the new satellites. Still, SDR is great fun. It's incredible to realize that all this information is stored in electromagnetic waves and passing through us all the time.
I was informed maybe 7 or 8 years back that my electric company would be replacing my analog meter with a smart one and always intended to try and glean more information about my electric consumption habits from it. It took me a lot longer than I intended, but last year I finally bought an RTL-SDR in the hopes of being able to get realtime info from the meter. Unfortunately, it seems that it's not one of the ones that emits consumption info over ISM bands for consumption by household appliances (so far as I can tell) and I ended up only capturing info from TPMS sensors off of passing cars (which was cool, but not really what I was looking for).
Do note that if you purchase an RTL-SDR these days, you'll probably get a v4 which, at least as of last year, does not play out-of-the-box at all with the software available on the Ubuntu apt repos and the RTL-SDR drivers that ship with 24.04 out-of-the-box — there were some hardware protocol/interface changes between v3 and v4 that make the old drivers incompatible and you'll get a litany of misleading or non-specific errors if you try without downloading and installing the latest drivers from GitHub (or somewhere).
Heya, author here! This was such a fun project, and I'd really recommend the "Make 50 Things of Something" technique to everyone!
Also, I gave a 10-minute talk version of this post at !!Con last year: https://www.youtube.com/watch?v=Xic63tHw2Bo
The paging system was unencrypted around here the last I looked (that was during covid). And there was software that could decode the transmissions. The SDR would easily pick it up.
One of the hospitals had been using it and would page people with PII -- including which people were in which room. So you could kinda see what was happening in the hospitals -- particularly during covid.
There kinda was a life cycle, seeing people admitted, O2 alerts firing off, and then the morgue being called to a room.
Overall, it was both interesting to have insight into something that you weren't ever going to be allowed to have access, and also very very sad.
Receiving 433Mhz sensor data using rtl_433[0] with an RTL SDR was a lot of fun when I started doing it last year. There's MQTT output if you want to send it to Home Assistant, et. al., as well as simple text output to stdout. It was great fun seeing my neighbors' sensors, tire pressure sensors in passing vehicles, etc.
There a ton of devices that use 433Mhz. You can also extend rtl_433 pretty easily.
A few years ago I used an RTL-SDR to determine if I had a water leak since my meter is one that broadcasts over 900mhz (iirc). I wrote a small program to parse RTL-AMR output into Prometheus metrics (real life gauges are just like Prometheus gauges, who would've thought) and tracked it over a week while I was away on vacation. No leak luckily.
RTL-AMR: https://github.com/bemasher/rtlamr
Astonishing! Thank you very much for sharing.. This sentence really stuck out for me - "I was proud! I was tired! I was amazed that all those things I received are all around us, everywhere, all at once – if you know where to look. :O"
Related. Others?
Fifty Things you can do with a Software Defined Radio - https://news.ycombinator.com/item?id=39728153 - March 2024 (40 comments)
I can highly recommend the book Practical SDR if you want to learn about SDR: https://nostarch.com/practical-sdr
I've been wanting to experiment with SDR triangulation. There are some off the shelf options, but I think it would be fun to cobble something together using dongles.
This page was very slow to load for me, probably partly because it's being hugged by HN. But it would help a lot if images had the `loading="lazy"` attribute, and if they were compressed to about ~100KiB each instead.
Note for anyone trying to receive lower frequency signals (below 10MHz): The supplied coaxial cable is really really lossy at those frequencies, a change of cable ought to make a big difference in what you receive.
Is it clear that the aviation or maritime communications are "not meant for the public" within the meaning of the German law?
I'm amazed to see that liveatc.net has no receivers in Germany, maybe a sign that other people also have this interpretation of the legislation?
I bought myself a Baofeng & a Quansheng radio just recently & love to hear aviation conversations & such .. sadly I wasnt't able to hear anyone else yet .. on PMR nor Freenet Super interesting !
>Klaus, Bernd, Jürgen and Horst were talking about antennas, relays, and Windows XP!
I was last active on HAM bands about 15 years ago, but that sounds about right. And the weather.
"Listening to “messages not meant for the general public” is not allowed in Germany, so of course I didn’t do that"
The treaty of Rome says otherwise. Germans too are free to receive.
I have a USRP B210 and its great fun for many things. One of my favorite things to do is create a small 2G GSM base station to use old phones!
Over a decade ago I played with SDR sharp and a tv dongle and got to listen to very cool stuff. I don’t know if SDR sharp still exists, I think it was closed source at the time but free. I remember one could use it to decode stuff and then map to virtual ports to redirect to other software that expected an input from specialized hardware like ship signals and stuff like that.
How does one use random wire antenna in an urban area!
Tried once and just got huge amount of noise all over HF. Except for a few strong shortwave and Amateur Radio stations, the rest of HF was pretty useless.
Even had decent ground plane and tuned it.
I have been feeding ADSB data to public feeds for almost two years now: https://i.imgur.com/p9dRiVP.png
It runs on an Orange Pi Zero 3 SBC.
People are commenting about issues loading the images leading to them abandoning reading the article. Here is a fully cached copy of TFA, but note that the videos (and images, but especially the videos) load _really_ slowly https://web.archive.org/web/20240317122351/https://blinry.or... (but they do load if you wait long enough).
Very cool post. If Jeff Geerling is reading this, I wouldn't mind watching a video on each of these ;)
Like 13 years ago when I was doing FPV I remember soldering my own skew-planar/quadrifilar antennas with bendable wire ha, the photo of the short yellow dipole reminded me of it. I think it's a dipole or double-dipole not sure.
edit: I think it's just a dipole
more than 15 years ago I got a chance to play with gnu radio and back then it was hailed as the next big industry.. fast forward, and beyond the hacking community (and the hobbyist), it still has not taken over.
What a great write. I fiddled around with RTL SDRs years ago, but never got so far.
Kudos on convincing me to try one of these dongles. This looks like a ridiculously fun project to do with the kids.
Pictures are loading at a crawl, had to bail because the layout kept rerendering.
Looks like hug of death strikes again!
Nice blog. It would be great if there was a table of contents to see everything at a glance.
Is there SDR for the GHz range of signals used by modern equipment?
Kudos! I needed a break from no.24 and am looking forward to reading the remaining uses. Awesome article and resource. Thank you.
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wow
I got a walkie talkie set as a Christmas present when I was 8. Which was kind of an evil thing to do given I had no siblings or friends to play with. One day I turned one set on and listened for a while and I thought I heard someone talking behind all the static noise. So I said something and was shocked to hear the voice talking back to me. Fast forward a few decades, next week is my wedding and that voice on the other side of the radio is my best man.