Things you can do with a Software Defined Radio (2024)
blinry.org
blinry.org
>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." : )
She said no.
Are you willing to say what happened afterwards?
one day I learned that you could tune in all sorts of non-TV frequencies. In particular, you could tune into any phone calls my neighbors were making on their wireless phones.
i loved that little tv and used it up until the conversion to digital OTA tranmissions.
Aside from dialing into late night TV programmes my parents prohibited, there were two buttons that switched between VHF and UHF.
Toggling the UHF button allowed me to tune into police radio.
Being able to capture this via that TV felt close to magic, and I think probably went a long way to forming my associations between technology, mystery and discovery.
We rarely used them much, since we were often walking in a family unit, so during one of our breaks I took one out, turned it on, and blasted off into the ether "hello hello, anyone out there wanna chat?" .. did this off and on for the afternoon, when suddenly, a voice answered back "yes! who is this?" ..
A family waaaaay the hell down the mountain rage, deep in the valley, had by chance heard my call .. so the boys spent the afternoon getting to know all of the 5 kids in that family that were all drawn to the conversation.
It was awesome, for the rest of the week, our kids and theirs just chatted away .. what had started out to be, a little bit of a mundane trip for the kids, turned out to be a hilarious social experience.
We call for them every time we're out that way - never met them, but for the past 3 years, the conversations have continued and it has been a great alternative to the mobile phones we have been troubled with up in the cabin, at times.
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
This is still happening? I'm sorry but that's hilarious!
https://www.rtl-sdr.com/hunting-for-space-radio-pirates-on-t...
prisoners of gravity: a favorite from_my_youth
1) https://inv.nadeko.net/watch?v=-deHrvY2b08&list=PL08AD26AD9C...
remotely read a nearby screen
Displaying malicious image causes HDMI cable to emit LoRa packets, https://github.com/XieyangSun/TEMPEST-LoRa
passive radar
SEC-T 0x11 (2025) on evil maid defense, https://www.youtube.com/watch?v=ScwNIWzk4RQ
> Do you like feeling safe about leaving your expensive stuff in your hotel room? Have you ever had anything stolen out of your room, or discovered someone has gained access to your room while you weren't there? .. what about .. other rooms? Maybe not EXACTLY a hotel room? I've presented on securing hotel rooms in the past, but adding home assistant, zwave devices, co2 sensors and millimeter wave radar it's become a whole new game
SDR is amazing!
> We use the GNURadio software along with RTL-SDR and ADALM-PLUTO hardware to explore the world of digital communication. We build up to a simple QPSK modem and rudimentary GPS reception.
LibreSDR firmware, https://github.com/F5OEO/tezuka_fw
> official [PlutoSDR] firmware updates are no longer focus on new features for SDR enthusiastic people.. tezuka.. aims to be Universal Zynq/AD9363 firmware builder for.. PlutoSDR, Pluto+, AntSDR (e200), LibreSDR
https://medium.com/@rxseger/receiving-ir-signals-with-rtl-sd...
As to connecting a photodiode to the antenna input, I don't see how that would work, but that may well be due to my limited understanding and imagination.
Do you mean using the photodiode in a photovoltaic mode? Also, presumably you'd have to bypass the tuner and hook to the direct sampling pins on an RTLSDR? Even with direct sampling, wouldn't the 38kHz of IR remote modulation get filtered out by the DC blocking?
https://www.youtube.com/watch?v=wIN7DVGBbKM
I imagine, provided the IR's frequency can be sampled by the SDR, it would look like fairly wide band bursts that could be decoded? Especially if you just treat the SDR as a ADC Oscilloscope
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.
If you squint enough there is nothing new under the sun and chances are that you will take a very long time to find something that hasn't already been done!
But doing your own product does several things - you learn a lot, you position yourself for future success, you see future ideas differently. And maybe you're okay for something to not be a billion dollar idea and you can outlast a venture funded product.
Maybe I'm just projecting, because I've put of building something for such a long time!
My actual "MVP" was some kind of automated neighborhood newsletter, that'd monitor emergency services radio traffic, and put together some kind of "here's what happened in your neighborhood" daily newsletter.
Maybe I could get it packaged in a hardware/software package that let anyone set one up in their neighborhood.
But I mostly got stuck in privacy concerns. I'm not sure it's a valuable public service to let people know that, for example, someone had a heart attack a few blocks over.
I did think about the scientific value of some kind of statistical database that process and recorded emergency services calls though. But mostly, my ideas for commercial and moral opportunities were half-baked at the point that I discovered citizen.
One of the technical challenges I came up against was finding transcription software that could semi-accurately transcribe UHF/VHF radio traffic. However, it looks like there's some progress that's been made there since I last checked: https://www.rtl-sdr.com/radiotransciptor-real-time-radio-spe...
In the moment, notifying people who know CPR and may be nearby and able to get to a nearby location and start CPR before emergency services arrives is the base of PulsePoint [1], which seems like a useful public service.
As a digest, yeah, I don't think any usefulness outweighs the invasion of privacy. Maybe just a count of health emergencies responded to for observing trends.
A real time, AI snips version for my area in a running feed would be amazing. There are lots of formats and use cases; and the info is already out there.
It’s a great idea. Don’t let citizen sway you away from it.
None of that is to say it isn't a good idea. I appreciate the ability to see roughly what is going on when I hear sirens. Even if the sites aren't always able to show the calls. I think highway patrol doesn't show up for me.
Regarding medical emergencies, I'm pretty sure EMS just says "medical emergency" and gives the address. I've never heard them say specific patient conditions, although sometimes the ambulance can forward that to the ER.
If there were any risk, it would be making it too easy for criminals to monitor and allow them to commit crime more effectively.
This is very good advice: we often give up on "great ideas" once we find that they have already been done.
But the vast majority of people we consider successful did not invent anything completely new, they just made a better kind of XYZ, sometimes not even that dramatically different. If you think about it, it's a much more logical path to success than expecting to be the next DaVinci.
You can easily distinguish yourself from Citizen by targeting a different demographic, different branding, different UX, interpreting the data in a different way.
Just look at how many businesses there are in any industry that deliver the same outcome for their customers but in a slightly different way.
What you're describing could be a really good news source giving live on-the-ground information to people.
Maybe instead of emergency services activity, it could be other types of activities (hazards, local events, nextdoor alerts, local business/SIGs rss feeds, etc), it is all just local info and knowledge aggregation endpoints and archives that have over-the-air and terrestrial distribution channels.
"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...
Maybe once they're turned off they're irrecoverable?
They'd more likely use higher bands on newer satellites to get more throughput. The GOES birds transmit up around 1.7GHz, afaik and likely higher as well.
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).
https://en.wikipedia.org/wiki/Broadband_over_power_lines
Thanks for correcting me on that.
Also, I wouldn’t have known the product exposes an API I could use to programmatically get the (XML-only?) usage data in realtime over the network if you hadn’t told me, the product listing makes it look like it’s just a screen (and the faq doesn’t have anything about connecting to the device programmatically).
Anyhow, thanks for brining this to my attention! This might be exactly what I was looking for!
Check with your electric company first, and also look at your local library -- my brother was able to borrow one from there to check compatibility first.
When I was installing it I actually came across the Ubuntu installation notes only to find I didn't need to do any of those things on my systems.
https://www.onesdr.com/rtl-sdr-vs-nesdr-which-one-should-i-b...
I'm looking at a bladeRF...
... sitting on a porch, yelling "Check your tires!" at random cars...
Also, I gave a 10-minute talk version of this post at !!Con last year: https://www.youtube.com/watch?v=Xic63tHw2Bo
There a ton of devices that use 433Mhz. You can also extend rtl_433 pretty easily.
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.
https://www.xylem.com/en-us/products--services/metrology-equ...
I know that it has a radio, but it might only transmit when it receives a signal from a vehicle driving down the street.
WAY cheaper than the other options too.
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.
The pocsag data, if this detailed, would have mentioned giving specific patients specific medicine that would then cause their O2 sat to drop. Since that isn't mentioned, either they forgot, or maybe there's an axe to grind.
Nevertheless, having grabbed pocsag in my area i don't remember seeing much PII, mostly room numbers, if anything.
There is no way that they will know or care if you don't share messages.
Fifty Things you can do with a Software Defined Radio - https://news.ycombinator.com/item?id=39728153 - March 2024 (40 comments)
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).
RTL-AMR: https://github.com/bemasher/rtlamr
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?
But apparently the government of Germany doesn't quite conclude the same thing from that which I do.
Similarly, the government of Germany (apparently?) seem to make the distinction that decoding signals from a neighbors IoT device is not restricted like other "messages not meant for the general public", so honestly there's probably a lot of nuance that a naive outsider is completely missing.
The law[1] is worded like this:
> (1) Mit einer Funkanlage (§ 3 Absatz 1 Nummer 1 des Funkanlagengesetzes) dürfen nur solche Nachrichten abgehört oder in vergleichbarer Weise zur Kenntnis genommen werden, die für den Betreiber der Funkanlage, für Funkamateure im Sinne des § 2 Nummer 1 des Amateurfunkgesetzes, für die Allgemeinheit oder für einen unbestimmten Personenkreis bestimmt sind.
The law basically says that you may only listen to (or take note of in comparable way[2]) messages that are:
1. For you, the operator
2. For amateur radio operators according to the Amateurfunkgesetz
3. For the general public
4. For an indeterminate group of persons (I think that's an accurate translation?)
For me, a big question regarding aviation and marine traffic monitoring is what "unbestimmten Personenkreis"/"indeterminate group of persons" actually means. Since "die Allgemeinheit"/"the general public" is listed separately, I'd assume it's a distinct group from that, and to me the previous commenter's "meant for any member of the public who happens to be flying a plane nearby" sounds like it could fit that description. I'd argue, for example, that police radio is for a "determinate" group of persons, police officers and dispatchers working for the government, whereas aviation and maritime traffic is an "indeterminate" group of people, people working for all sorts of airlines, shipping companies, recreational pilots/boaters, who happen to be around the same area.
If anyone has any links to cases where this law was tried in relation to aviation or maritime communications, please share them, I have been struggling to figure out where to look for this stuff, on top of that, the law was also renamed or moved around, which makes it extra confusing.
[1] https://dejure.org/gesetze/TDDDG/5.html
[2] Might be related to this weird ruling, where a judge in a case about some ADS-B receiver decided that it was ok because rendering the position of aircraft wasn't "listening to" (as in, literally hearing) the traffic: https://openjur.de/u/130555.html - This decision is probably moot now, due the addition of "take note of in comparable way". The judge briefly mentions that actually listening to the traffic could be violating the law, but I am not sure if this point was ever properly litigated.
It runs on an Orange Pi Zero 3 SBC.
The treaty of Rome says otherwise. Germans too are free to receive.
I was last active on HAM bands about 15 years ago, but that sounds about right. And the weather.
edit: I think it's just a dipole
Just curious about if the original title was rule breaking or something.
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.
TL,DR: you probably don't want a random wire for HF reception, but either an E-field whip antenna like that one, or an H-field loop which will likely be larger and more expensive, but will have useful directional properties that the whip will not.
But for the normal users - to be honest - most topics are too heavy on complex math. And there's no way to avoid it if you want results.
Most advanced radio stuff much more complicate than checking out a repo from GitHub and compiling it.
That being said last I used it extensively was v3 so maybe v4 is better. Did they get rid of thread per block and allow you to have a single thread service a sub signal chain? I remember that the number of context switches between threads, and balancing latency vs buffer sizes was a pain in the rear.
It's great fun for doing signal analysis, but I'd never want to try and implement a full-duplex communication system in production with it.
Looks like hug of death strikes again!
The AD9363 stock is only supposed to be 325mhz to 3.8ghz but stuff like the plutoSDR which uses it manages to get the transceiver all the way from 70mhz to 6ghz like the more expensive AD9361 used in the real USRP B210s
Benefit is you can transmit stuff too, not just receive unlike the RTL-SDR which is RX only
You can tune into remote SDR’s people set up to work with this data without having your own device or download recordings others have made.
It is this raw sample data that you then demodulate according to whatever scheme required on the PC side.
A great resource I found was pysdr.org. I had absolutely no background in RF and very little python experience but that guide explains everything from the ground up from how the IQ samples are physically generated and read in an antenna, all the modulation schemes you mentioned, and how to code useful things with the various devices. No affiliation but a great resource.
https://www.ntia.gov/files/ntia/publications/2003-allochrt.p...
years ago, there used to be a very abundant market for used or chinese clone HackRF One units, but i haven't been able to find any these days.
[1]: https://www.nooelec.com/store/sdr/sdr-addons/ham-it-up.html
FM wideband is something like 88-108MHz.
108-137MHz is a lot of aviation traffic.
7-144MHz lots of long range DX.
Then the 144-148 amateur band.
151-154 Multi Use Radio Service
433MHz has all kinds of sensor data from the world around you.
462-467 Family Radio Service (FRS) / General Mobile Radio Service (GMRS).
900MHz area has different types of beacons, cameras, etc.
1090 for Aviation beacon ADS-B
For other freqs you can often use an upconverter or downconverter to hit the freqs you need.
Examples: https://www.nooelec.com/store/sdr/sdr-addons/upconverters-do...