Things you can do with a Software Defined Radio (2024)
54 comments
·September 16, 2025tedggh
mtlynch
Congrats! That's such a cool story!
>Fast forward a few decades, next week is my wedding and that voice on the other side of the radio is...
I think I've seen too many rom-coms because I was sure this sentence going to end with "my fiance." : )
brulard
I expected the voice on the other side being your soon-to-be wife. But good story nevertheless. Congrats!
behnamoh
This is awesome, and congratulations!
fullstop
This is awesome, and future congratulations on your wedding!
thenobsta
I got chills reading this. Congrats!
ComputerGuru
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 433mhz 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).
vel0city
A number of smart meters communicate over the mains wires, especially when they're in very sparse areas. There was even a thought for a bit to offer internet services over the power distribution cables, but I don't think they ever really got effective data rates high enough to be competitive.
ComputerGuru
Yes, that seems to be what mine is doing as my ecobee thermostat is able to read info about peak usage times from the mains. I didn't know about the latter part though, I never imagined electric companies were making a play for the internet (though it seems like an obvious thought in retrospect).
megaloblasto
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.
egorfine
I wonder what does it entail to have a NOAA satellite decommissioned? Is it just turned off or is it directed to fall down into a designated area in the Pacific?
megaloblasto
They will continue to orbit for about 150 years, slowly falling towards earth until the drag from the atmosphere burns them up.
"Like many older satellites, the POES satellites do not have thrusters to support a controlled reentry into Earth’s atmosphere at the end of their mission life. Instead, once passivated, they are safely powered down, placed in a non-operational state, and left in a stable orbit. Without onboard propulsion or significant atmospheric drag at their current altitude, NOAA estimates they will remain in orbit for roughly 150 years before gradually reentering the atmosphere and disintegrating."[1]
[1] https://www.nesdis.noaa.gov/news/legacy-orbit-noaa-decommiss...
egorfine
It sucks they power it down
gmiller123456
I depends on the orbit. The low Earth ones would usually be de-orbited and fall back to Earth. The geosychronous ones are usually just moved to a parking orbit out of the way to make room for more. If it's in a high but not very crowded orbit, they might just stop using it.
ComputerGuru
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).
ortusdux
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.
colanderman
https://khanfar-spectrum-analyzer.web.app/ also has some phase-based direction-finding software and upcoming hardware.
For triangulation though, if you have a reference signal at a known location, TDoA (time difference of arrival) requires less hardware (just a single receiver at each location, e.g. an RTL-SDR). I don't know of any open-source software which does that though I've been slowly building some for my own use (it's pretty janky at the moment).
_whiteCaps_
One of the people in my local radio club did a demonstration of tracking down a commercial operation using amateur radio frequencies with the KrakenSDR. It's very impressive. I think the timing would be much more difficult using off the shelf dongles.
najarvg
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"
EvanAnderson
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.
rpcope1
A lot of the 433/915 band devices you can pick up with rtl_433 seem to be much more bullet proof and have longer battery life than equivalent WiFi and Zigbee devices too. Building new protocol decoders for rtl_433 also surprisingly isn't too bad either. One of my favorite ones is the water meter decoder which has saved me a lot of money when I've had irrigation water leaks and not noticed them (but saw conspicuous usage patterns reported).
fullstop
I was hoping to find more devices around me which use 433. Apparently my neighbors don't have any 433MHz devices.
EvanAnderson
I'm spoiled. One of my receivers is on a second story and has great line-of-sight to a bunch of houses and a parking lot (where I assume I get a lot of my TPMS "hits").
fullstop
I was able to read some data from my electric meter, but the good stuff is encrypted.
What I was _really_ hoping to read was my water meter. It transmits so infrequently, though, so it's hard get much of anything or even know if you're successfully receiving something more than noise.
lpln3452
Nice blog. It would be great if there was a table of contents to see everything at a glance.
null
fullstop
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.
ge96
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
a1o
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.
sharksauce
There is SDR++ : https://www.sdrpp.org/
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.