blinryI want to try the "make 50 of something" technique again!
So this week, I'll try to find 50 things to do with a Software Defined Radio! 📻
I'll use this simple USB dongle, which you can get for around $30.
1: Listen to FM radio
This is an obvious first thing to do, as the signals are very strong!
I'm using the SDR++ software, and it feels very nice browsing around and discovering the stations around you!
I found a local station that gives 1-hour slots to civic groups, for example!
I'm using a dipole antenna that came with the kit I purchased.
You generally wanna make it half as long as the wave length you want to receive, which is around 3 meters for FM radio.
2: Listen to Freenet
This is a special frequency range in Germany: Anyone is allowed to send there, using licensed devices. There are 6 channels.
I think someone's testing their device there right now. :D I heard a "Hellooo?", then a "Test, test", and then a "General call to all stations". Oh, and just now a short transmission on channel 3 in a Slavic-sounding language!
Freenet devices have a range of only a couple of kilometers, so these people must be pretty close! :O
3: Receive weather conditions from airports
While browsing the aviation frequencies, I found this station that reports weather conditions in an endless loop. It seems to be the "Automatic Terminal Information Service" of Hamburg airport!
Thanks to that, I now know that the current air pressure is 1011 hPa! :D
4: Listen to airplane communication
Listening to "messages not meant for the general public" is not allowed in Germany, so of course I didn't do that. And if I had accidentally done that, I wouldn't be allowed to tell you about it. 🙅
5: Track aircraft via ADS-B
That's short for "Automatic Dependent Surveillance – Broadcast". Aircraft send it automatically to be tracked.
For this, I built my first antenna! From wire and and an antenna connector called "SMA". And it works! \o/
I'm decoding the signal using the software SDRangel. Fascinating! I see some big & small airplanes, and even a helicopter!
6: Listen to *stereo* FM radio
How stereo audio is transmitted is really interesting, because it's backwards-compatible to receivers that don't support it:
Here, you see the demodulated audio frequency spectrum. Below 19k Hz, it's just mono audio. Then, to mark a stereo station, there's a constant "pilot tone" at 19k Hz! (Outside of what most humans can hear.)
Then, if you double the frequency of the pilot tone, you can derive the sections where the left & right channel is transmitted!
7: Receive road traffic information
If you triple the frequency of the pilot tone, you get to a range where FM stations transmit small amounts of digital metadata, like the name and genre of the station, and the current song! That's a protocol called Radio Data System.
This system can also transmit road traffic information! There seems to be a road closure at "0x64BE". The Federal Highway Research Institute publishes an Excel table, where I could look up that this is a town in Lower Saxony!
8: Listen to conversations on the 2-meter amateur radio band
This is a frequency range reserved for amateur radio operators – for non-commercial use only. You may send on this band after getting a license.
What I found here is seemingly a conversation circle facilitated by a relay around 15 km away from here – it takes input on a certain frequency, and outputs an amplified copy of it on another frequency! Klaus, Bernd, Jürgen and Horst are talking about antennas, relays, and Windows XP! 😁
9: Listen to digital radio
The SDRangel software also has a demodulator for Digital Audio Broadcast! :O I continue to be amazed by it!
I think this is the first time I've received digital radio via air! Whoa, I see so many stations, and I've only checked a couple of channels.
The advantage of this digital channel is that there's no noise. And I even saw a "cover image" in one of the programs!
10: Listen to PMR446
This is a frequency range for "Private Mobile Radio". It's another of these bands where anyone can transmit using a licensed device!
Not a lot of activity here. I heard "Hello, hellooo!", "Can you hear me?" and some short transmissions that sounded like a child! :D
There also seem to be digital transmissions, but I don't know how to decode them yet.
The range of PMR446 devices is pretty low (a couple of hundred metres in cities), so again, the people must be close!
With that, I end the first day of SDR experiments! :) It's amazing to me how much invisible communication is going on around us in the electromagnetic spectrum at the same time!
To be continued tomorrow. Feel free to suggest things I could receive!
11: Read your neighbors' sensors
At 433 MHz, there's a frequency band for "industrial, scientific and medical" applications. And wow, there's quite a lot of activity nearby!
Using the decoder rtl_433, I see two sensors that output the current temperature, humidity, and air pressure!
There's also some "IBIS beacons" flying by, which are used in public transportation, so maybe it's buses driving by?
And just now, an "Interlogix Security" device appeared, reporting "closed switch states" :O
12: Track ships!
They send out their status using AIS (Automatic Identification System). And again, I receive *a lot* of them here in Hamburg! :O
I was especially excited to receive data from @msstubnitz (a fisher boat that was turned into a culture center/techno club)! It reports its status as "moored", and its speed as 0.1 knots! :D
This is again the software SDRangel. Apparently, it can also display a 3D map, but I haven't figured out how to add 3D models…
13: Detect GSM activity
I was curious whether you could tell if someone used their phone!
So I borrowed a GSM phone, tuned to the correct frequencies, and made some test calls.
What surprised me most: You can kind of "see" the volume at which I was talking!?
In the recording, the three dense bands at the end were when I was humming into the phone at the other end. This only worked in the "receiving" direction.
By the way, I try to adjust my antenna to the desired frequency as best as I can.
For GSM, I used the tiny screw-on antennas from the kit! :)
14: Receive signals from a satellite!
The program gpredict is really nice to find out when satellites will pass overhead! Learned lot yesterday, including that one satellite I was trying to receive burned up last week! :D
I was super excited when I first received a signal from a NOAA satellite! 🛰️
But I didn't manage to decode it properly yet. Maybe my reception is too noisy? I wanna keep trying, but I gotta move on.
15: Admire TETRA signals
In Germany, the police has switched to an encrypted digital protocol called TETRA.
Even though I've seen some interesting talks at CCC events about weaknesses in the decryption, all I wanna do for now is look at the pretty signals in sdrpp. :3
16: Listen to taxi dispatchers
Again, this is communication not meant for the general public.
I didn't just listen to someone dispatching taxis to specific addresses, and you also shouldn't do that either. 🚕
Stay away from a site called "frequenzdatenbank"!
17: Ponder mysterious signals
Some of the most fun I'm having is just browsing frequencies and seeing what I can find!
Sometimes, I encounter signals I can't identify.
For example, at 865-868 MHz, there's a family of slow, continuous, digital signals that make a nice melody when listened to in single-sideband demodulation!
And at 177-180 MHz, there's two very broadband transmissions. Might be TV? But I can't find out what type.
If you have ideas, let me know! :) Time for lunch!
18: Track weather balloons
A radiosonde was just launched in Hamburg! SDRangel can decode its transmission! It has climbed to a height of 5 km, and it's -17 °C there!
Um, I could try to get it after it bursts and lands. Should I go get it?!
Ohhh, the balloon popped earlier than predicted! *frantically changes travel plans*
It landed in a forest. Hope I can get to it.
Didn't find the sonde. But something that might be even better – a friend!
On my way back, will report more soon. Data volume is used up, smartphone battery is empty.
So, the full story: I made my way up to the landing site by subway, train and bike.
As I circled the site, I encountered a person in their 60s, with a stubbly beard and a blue wool hat. He was looking in the direction of the crash site, and was holding a smartphone, so I asked him whether he also was looking for the radiosonde.
He was! We looked for it together for half an hour, jumping over small rivers and crawling through the woods, while he gave me a lot of tips related to hunting sondes.
He told me that he had found around 40 of them so far!
Usually, the sondes keep broadcasting after landing, but this one wasn't. So he quickly guessed that someone else could've taken it. Or maybe it landed in the water and died?
Eventually, we gave up, and walked back to our vehicles. He also is an amateur radio operator, and could answer a couple of questions related to building antennas!
And he was right: Someone had been faster than us! The status was changed: https://radiosondy.info/sonde_archive.php?sondenumber=V2930794
Some pictures from the landing site!
And I think I have earned this:
19: *Hunt* weather balloons!
20: Receive amateur packet radio
In the 2-meter amateur band, there are certain frequencies for the "Automatic Packet Reporting System". It's a bit like IP – packets have a "from" and a "to". They can also broadcast their position, or weather data.
Some stations seem to announce themselves as repeaters, which probably help forward the packets to increase the range.
And two people seem to be on a "fieldday", and broadcast their location. :D
SDRangel can create a map automatically:
This is going to be a simple "random wire" antenna, to allow me to get better reception in the lower wavelenghts, which I've omitted so far.
I've measured out 21.6 m of wire (which for ✨magic✨ reasons seem to be a good universal antenna length)...
utzer 
@blinry very cool.
Daniel Bohrer@blinry awww 😊 have a good way home!
stodarahodan@blinry always wondered where people find these „friends“
Leah@blinry Hm weißt du warum der Burst und das Landing wo ganz anders angezeigt wird als der orange Track?
@leah Das orange ist ne statische prediction, die sich seit Start nicht verändert hat. Vllt zu rechenintensiv, das live neu zu berechnen?
Marcus Müller@blinry Before you're done with 50 using demodulators that others wrote for you,:
quite a nice (and fast-to-read) intro to the theory: https://pysdr.org
"build your first receiver for your wireless doorbell¹" may be quite doable following https://tutorials.gnuradio.org
You'll also like @destevez 's blog on decoding recent moon etc missions https://destevez.net/ &his sat telemetry rx https://github.com/daniestevez/gr-satellites/
—
¹assuming it does smth simple and not zigbee, but then again,gr-ieee-802-15-4 exists
@blinry for all questions regarding GNU Radio and how to use it with an RTL dongle (hint: our all-in one installers, and most Linux distro packaging bring all the driver interfaces and often even the rtl driver itself with it, one-stop shop installation!), the wiki, the [email protected] mailing list and the matrix://chat.gnuradio.org chat server are quite helpful.
No matter what you do: Have fun!
shoc Inc, Rolf Haenggi
zwangseinweisung@blinry think about the upcoming strike ;)
Kevin Karhan 
@blinry Shure...
I'm convinced @DeutscherWetterdienst or whoever launched it has some tags on it and would very likely reimburse you for sending it back to them for reuse...
gnarf@blinry Oh boi, you're getting yourself into quite the rabbit hole. A friend of mine is addicted to catching weather balloons but there's also a very active OM (old man) in the area. Sometimes they race each other at 3 AM. Friend has the advantage of a better weather prediction model, OM has the advantage of not caring about the speed limit. It's quite even, I'd say :)
Friend has collected >100 probes and desolders the STM from them to use in random projects
Friend has collected >100 probes and desolders the STM from them to use in random projects
@blinry I was also part of a high-altitude balloon experiment of a local university. It was loads of fun trying to chase the balloon over several 100km with friends. We had three chase cars and split up to increase chances to be within visual range during landing. But climbing up some trees to get the precious science data is definitely the best part 
sebastian ⚡@gnarf
Been there, done that. But I usually chose to track them from home until the transmitter turns off, and then I go looking for them as soon as I have some spare time. Geocaching with extra difficulty. The nice thing here is that the folks launching the balloons know about the HAM operators chasing them. So sometimes they include a little easteregg.
@blinry
Been there, done that. But I usually chose to track them from home until the transmitter turns off, and then I go looking for them as soon as I have some spare time. Geocaching with extra difficulty. The nice thing here is that the folks launching the balloons know about the HAM operators chasing them. So sometimes they include a little easteregg.
@blinry
~n@blinry Shamelessly hijacking your thread… but bearing a nice spectrum graph while doing so!
Does anyone know what this one in the upper region of 800MHz might be?
Does anyone know what this one in the upper region of 800MHz might be?
2342@nblr clearly a weather balloon.
@nblr @blinry can't really tell what the frequencies and bandwidths here are, could you illuminate? These could both be wide-area low-power networks, or some private control that use some frequency hopping or many users with discrete channels that only sparsely transmit, depending on the actual band (Frequenzplan der @BNetzA is your friend, as usual)
lynxis@lynxis @nblr @blinry @BNetzA @spmrider jap, hier sieht man sehr schön die rechteckige spektrale Form von OFDM! Auch das burstige Verhalten passt; im downlink wird schön ofdma gemacht, sprich die verschiedenen Signale für verschiedene Endgeräte werden einfach auf unterschiedliche Zeit/Frequenzblöcke in ein und demselben ofdm frame gepackt.
Im Uplink scheint das 3gpp Release 10 oder früher (iirc) zu sein, wo man wegen des da verwendeten (single Carrier)fdma unterschiedlichen Teilnehmern...
@lynxis @nblr @blinry @BNetzA @spmrider ... Tatsächlich unterschiedliche Frequenzen gibt. Was mich davon überrascht ist die ungleiche Verteilung von den Leistungsdichtespitzen in einer Richtung, im Vergleich zur anderen!
Das sieht man normal nur, wenn der Beobachter nah an allen beabsichtigten Empfängern ist, also im Uplink nah an der Antenne von der Basisstation, und im Downlink man etwa gleich weg von der Basisstation ist wie *alle* Teilnehmer. Grund ist, dass beide Seiten nur gerade so viel…
@lynxis @nblr @blinry @BNetzA @spmrider
Leistung für die jeweils andere rausballern, wie nötig ist, um die gewünschte Übertragungskapazität zu erreichen (ist auch soweit ganz logisch, das Handy mit Akku will nicht, wenn's direkt an der Basisstation sitzt, brüllen als wär's am äußersten Rand der größtmöglichen Zelle, und die Basisstation will auch nicht, dass total laut dröhnende nahebei-Handys die noch gerade detektierbaren Signale der fernab-Handys kaputtmachen. Und Strom für Basisstationen…
Leistung für die jeweils andere rausballern, wie nötig ist, um die gewünschte Übertragungskapazität zu erreichen (ist auch soweit ganz logisch, das Handy mit Akku will nicht, wenn's direkt an der Basisstation sitzt, brüllen als wär's am äußersten Rand der größtmöglichen Zelle, und die Basisstation will auch nicht, dass total laut dröhnende nahebei-Handys die noch gerade detektierbaren Signale der fernab-Handys kaputtmachen. Und Strom für Basisstationen…
Oliver Brandmüller@spmrider Would love to get some pointers on spectrum currently used for lorawan stuff. Haven't seen it knowingly yet.
@nblr
863-870 MHz in EU, typical channels that must be supported by all devices are 868.10 MHz, 868.30 MHz, 868.50 MHz with 125kHz. Your antenna and RF should be able to receive RSSI as low as -120dBm or even less, LoRaWAN devices usually only send at 14dBm / 25mW
863-870 MHz in EU, typical channels that must be supported by all devices are 868.10 MHz, 868.30 MHz, 868.50 MHz with 125kHz. Your antenna and RF should be able to receive RSSI as low as -120dBm or even less, LoRaWAN devices usually only send at 14dBm / 25mW
@nblr
Remember, it's ISM Band, you'll see a lot of other stuff there (home automation, zigbee, zwave, thread ...)
Remember, it's ISM Band, you'll see a lot of other stuff there (home automation, zigbee, zwave, thread ...)
SebastianRTSA-Suite PRO Spectrum Analysis Software - Aaronia AG
RTSA Suite PRO is the world's fastest real-time spectrum analysis software on the market and has been specially developed for our latest SPECTRAN® real-time devices. It makes it possible to integrate various hardware components and use them for analysis.
@moehrenfeld @blinry Beyond realtime 🌈
@moehrenfeld @blinry Some modules cost extra. It only works with the Spectran v6 series.
@moehrenfeld @blinry If you do… It‘d be money well spent, ngl.
These devices are a delight!
That being said... comparing @blinry's graphs and the one from the spectran shows how good inexpensive gear is these days. The qualitative difference is negligible for most purposes (sadly not for mine, but then again work vs. hobby usage and budget).
Most of the price difference goes into 2.4MHz vs. 80MHz sampled bandwidth.
These devices are a delight!
That being said... comparing @blinry's graphs and the one from the spectran shows how good inexpensive gear is these days. The qualitative difference is negligible for most purposes (sadly not for mine, but then again work vs. hobby usage and budget).
Most of the price difference goes into 2.4MHz vs. 80MHz sampled bandwidth.
dl8laq
ttk (DO1TTK) 
@blinry idk but the image reminds me of the first Donkey Kong arcade game :D
Beko Pharm (deprecated)@blinry also useful to read out these pesky TPMS IDs your garage forgot to tell you about so you can write back that information twice a year to the CAN bus of your car when tires are switched for the wintertime and vice versa saving yourself ~90 bucks __each time__.
Looking at you Renault!
@blinry Try them with gradually more extension and see if it makes a difference.
That's something that took me quite a while to wrap my head around: Most of the time the antennas resonance frequency is not as critical for receiving. For transmission you'd notice a more drastic difference, but for receiving, especially for stronger signals, most antennas tend to work okay if they are close enough frequency wise.
On the other hand having your antenna resonant in a small band can prevent it from picking up noise and other unwanted signals. So you might be able to spot that change in the level of noise floor or when listening to weaker signals.
Definitely a worthwhile experiment to get a feel for the equipment.
That's something that took me quite a while to wrap my head around: Most of the time the antennas resonance frequency is not as critical for receiving. For transmission you'd notice a more drastic difference, but for receiving, especially for stronger signals, most antennas tend to work okay if they are close enough frequency wise.
On the other hand having your antenna resonant in a small band can prevent it from picking up noise and other unwanted signals. So you might be able to spot that change in the level of noise floor or when listening to weaker signals.
Definitely a worthwhile experiment to get a feel for the equipment.