Over on YouTube, user superkuh2 has posted a video showing off osmocoms gr-fosphor GNU Radio block which shows a real time spectrum visualization using the GPU. He combines gr-fosphor with multimode for visualizing the ISM and pager bands with his RTL-SDR.
Over on Gough’s Tech blog, Lui Gough has posted about his experiences with visualizing broadcast satellite signals with the RTL-SDR. In his post he shows how to receive broadcast satellite signals by using a LNB, or low noise block downconverter, which allows the RTL-SDR to receive satellite frequencies which are typically out of the range of the RTL-SDR.
Later in the post he also shows what several broadcast satellite signals look like on the waterfall, as well as some of their telemetry signals.
Hackaday brings to attention a simple hack where hacker Marc uses an antenna connected to a general purpose I/O (GPIO) pin on his Raspberry Pi to wirelessly transmit a wav file via AFSK modulation to his RTL-SDR. He uses a program called minimodem to encode the wav on the Raspberry Pi and then on the PC to decode the data received by the RTL-SDR.
Using this method, it is claimed that a signal can be transmitted up to 50m away, even through walls.
A while back we did a small write up on receiving and analyzing cellular GSM signals with the RTL-SDR. Now blogger Domi has taken it further and has done an excellent big write up on his blog showing how to receive, decode, and also decrypt your own cell phone GSM signals with the RTL-SDR.
Domi’s big write up is split into four posts. It starts with an introduction to GSM, then focuses on setting up the environment and required software, then uncovering the TMSI (step to be released later), and then finally shows how to actually receive and decrypt your cell phone data such as voice and SMS messages.
Dr. Carles Fernandez-Prades, Dr. Javier Arribas and Dr. Pau Closas have published an academic paper showing how they were able to implement an RTL-SDR based GNSS (Global Navigation Satellite System) receiver in software.
What they have done is use their open source GNSS software receiver program with a RTL-SDR connected to an active GPS antenna. An active GPS antenna requires DC power to be passed to the LNA in the GPS antenna through the antenna connection, so a Bias-T network is required to ensure DC power does not enter the RTL-SDR dongle.
More information can be found on their webpage here.
D-STAR or Digital Smart Technologies for Amateur Radio is a digital voice and data protocol used in amateur radio. I was tweeted a link earlier which shows how the RTL-SDR can decode D-STAR text messages and headers (link is in Italian but Google translate can help, and the pictures show more than enough information). By using SDRSharp and stereo mix you can tune to a D-STAR signal, and pass the audio to a command line based decoding program (dstar.exe) which can be downloaded from the above link, which will then decode D-STAR text messages.
Here is also an older video showing D-STAR decoding with HDSDR in action.
Wavesink is a new SDR Android App, which allows your RTL2832U based dongle to receive FM radio with RDS, Digital Audio Broadcast Radio (DAB) and VHF band Digital Radio Monodial (DRM+). DAB+ support is also to be released by next week, and a station memory will also be added in a future release.
The app is currently in beta development, and only the trial version is released, which will allow you to use the app for 5 minutes at a time. They indicate that the commercial version will be out soon.
To use this with your Android device, you will need a USB OTG (On the Go) cable, and your device must support USB host mode, which most Android devices above 3.1 should support.
I gave the app a quick spin in FM mode, and found that the interface was a little clunky, but the app worked fine, and the FM and RDS signals were decoded correctly.
Oona has written on her blog www.windytan.com about how she used an RTL-SDR to listen in on those wireless devices that are given out at some restaurants and cafes to notify you when your food is ready.
While at a local burger chain she found a label on the back of the device given to her which specified the radio frequency used by the device. By tuning to that frequency with her RTL-SDR, she discovered that the device uses the POCSAG protocol, which is the same protocol that is used by pagers. She then decoded the data packet and found that it contains the device address, which is used to notify the correct device.
