Category: Digital Signals

ADS-B Decoder for the RTL-SDR now available for Android

A (beta version) of an ADS-B decoder and display app for the RTL-SDR dongle for Android has been released. This app allows you to receive the ADS-B radio signals emitted by modern aircraft, which contain information such as flight number, latitude, longitude and altitude, essentially giving you a live portable aircraft radar.

To use the app, you will need an Android device that supports USB OTG, which most Android devices on Android 4.0+ should support. You will also need a USB OTG cable, and an RTL-SDR dongle. You may want to consider a USB OTG cable that has a second port for external charging capabilities, as the RTL-SDR can drain the battery quickly.

The app is cheaply priced at under $2, so give it a try!

ADS-B Decoding on Android
ADS-B Decoding on Android

Using the RTL-SDR to listen to the Funcube Satellite

Recently, the FUNcube-1 satellite was successfully launched. The FUNcube is a CubeSat (a low cost miniature 10cm cube sized satellite) which is intended mainly for educating young people about radio, space, physics and electronics, but has also piqued the interest of amateur radio hobbyists.

Amateur radio hobbyist N4JTC’s has shared on his blog his experiences with receiving the FUNcube-1’s telemetry using his RTL-SDR dongle. By using the RTL-SDR to receive the telemetry beacon as the satellite passes overhead, he was able to use the FUNcube Dashboard software to record and decode and view the satellites telemetry data.

Receiving the FUNcube-1 Satellite
Receiving the FUNcube-1 Satellite

Demo of Osmocoms ‘Phosphor’ Spectrum Visualizer

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.

osmocom's fosphor with patchvonbraun's multimode looking at ISM + FLEX pager bands with rtlsdr

Visualizing Broadcast Satellite Signals with the 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.

Visualizing Satellite Signals
Visualizing Satellite Signals

Transmitting Data with a Raspberry Pi and RTL-SDR

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.

Raspberry Pi Transmitter
Raspberry Pi Transmitter Received with RTL-SDR

Receiving, Decoding and Decrypting GSM Signals with the RTL-SDR

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.

GSM Decoding with Airprobe and Wireshark and RTL-SDR
GSM Decoding with Wireshark

Using the RTL-SDR as a Software GPS Receiver

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.

Rtlsdr_with_lna_patch_GA27

Decoding D-STAR Headers with the RTL-SDR

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.

dstar7

Here is also an older video showing D-STAR decoding with HDSDR in action.