Category: Applications

New Web Based RTL-SDR Remote Control Software: YouSDR

Recently Kristian, a reader of our blog wrote in to let us know about a new software project he found that allows you to use your RTL-SDR remotely through a web interface. The web interface runs on Linux and uses mysql and the Apache server to work. Currently it can be used to access options for rtl_fm, rtl_tcp, dump1090 and can also be used to create an icecast audio stream.

The software can be downloaded from its Git at https://github.com/sixuniform/yousdr. The instructions on the GitHub page show how to set it up on a Raspberry Pi running Raspbian, but the instructions should also be valid for other Linux distributions. As the software is new the authors are welcoming any improvements and feedback.

Some similar web based RTL-SDR remote control software that you may be interested in includes WebRadio and rtl_fm_python.

The YouSDR web interface.
The YouSDR web interface.

Decoding and Plotting VOR Signals with an RTL-SDR: Part 4

Previously we posted about Will’s (aka hpux735) project [1] [2] where he has been using an RTL-SDR dongle to help understand and decode aircraft navigation VOR signals. VOR is an acronym for VHF Omni Directional Radio Range and is an older method of navigation used by aircraft which is used to provide a heading towards a VOR transmitter.

In his latest video, Will has been able to finish his code which allows him to actually plot some VOR data that he obtained from a flight on a map. In the video the VOR data is used to draw a heading line between three recorded VOR transmitters and the aircraft. The video clearly shows the accuracy of the VOR signals (about 1 degree) and shows what happens to the heading accuracy when reception is bad.

VORs and SDRs Part 4: Fusion!

Fingerprinting Aircraft with Aircraft Scatter

Over on a Finnish aircraft spotting forum, one poster OH7HJ has been using the “Aircraft Scatter” technique to fingerprint individual aircraft (in Finnish, use Google Translate to read in English). Aircraft scatter is a method that can be used to detect aircraft via strong radio signals that are reflected by the aircraft body. OH7HJ shows that each different type of aircraft will present a different reflection intensity at different points of the reflection, allowing each aircraft to be uniquely identified.

In the thread the original poster used a standard hardware radio, but an RTL-SDR dongle or other software defined radio could also be used. He tuned to a strong analogue TV carrier and plotted the audio spectrograph in Spectrum Lab. If analogue TV is no longer available in your country other strong signals such as amateur radio beacons or radar signal carriers could also be used for aircraft scatter.

Below we show a small selection of some of the interesting images from page 9 of the thread, please see the actual thread for the rest. There is also more information and images contained in the other pages of the discussion thread too.

Fingerprinting a Boeing 777 with Aircraft Scatter
Fingerprinting a Boeing 777 with aircraft scatter
Comparing Aircraft Scatter Intensity Profiles
Comparing aircraft scatter intensity profiles
Comparing large and small aircraft with aircraft scatter
Comparing large and small aircraft with aircraft scatter

Listening to an NFC Polling Signal from a Nexus 7 with an RTL-SDR

Over on YouTube user 2e26tenW has uploaded a video showing reception of the second harmonic of an NFC polling signal with his RTL-SDR. NFC stands for “Near Field Communication” and is a technology that enables smartphones and other devices to communicate with one another and some smart cards simply by bringing the two devices together.

In his experiment he uses a Nexus 7 tablet to poll an NFC enabled transportation card. As the RTL-SDR cannot receive the NFC frequency of 13.56 MHz directly without an upconverter or hardware or software direct sampling modified dongle, 2e26tenW instead tunes to the second harmonic at 27.12 MHz which allows him to receive the signal.

Nexus 7 NFC polling signal (2nd harmonic)

Video Showing Decoding of DGPS Beacons with SDR# and MultiPSK

Following on from our last post where dewdude showed how to decode DGPS signals, Frank K2NCC has uploaded a video on YouTube showing DGPS decoding in action. In his video Frank uses an Airspy plus ham-it-up upconverter, a Sirio discone antenna and for software he uses SDR# with audio piped into MultiPSK for decoding.

In the video you can clearly see the decoded DGPS messages showing the pseudorange corrections and station numbers. To decode DGPS with MultiPSK you will need to use the paid version which costs approximately $50 USD, however in the free version the DGPS will run for 5 minutes each time MultiPSK is opened before expiring.

Below is an example of a decoded message.

24/03/2015 02:06:09
Message type        : 9 (GPS partial correction set)
Station number      : 172 (Appleton WA USA 300.0 Khz TXID 871 100bps)
Z-count             : 4215 ( 42 mn 9.0 s )
Sequence count      : 2le factor=0.3)

Sat. ID|SF|UDRE|Pseudorange corr.  |Range rate corr.|IOD|CRC
25     |0 |1-4m|      -7.68 m      |   0.000 m/s    |62 |OK
31     |0 |1-4m|       1.54 m      |   0.000 m/s    |27 |OK
32     |0 |1-4m|       0.70 m      |   0.000 m/s    |99 |Error

Decoding Differential GPS Beacons with an RTL-SDR, Speclab and SDR#

Over on his blog “RTL-SDR DX” dewdude has been exploring the reception and decoding of Differential GPS (DGPS) signals. DGPS signals are transmitted by government authorities in the long wave band at around 300 kHz. These beacons are used to dramatically improve the accuracy of GPS (Global Positioning System) devices from their default accuracy of about 15 m down to about 10 cm. Unlike GPS signals which originate from satellites, the DGPS signal is terrestrial based and is broadcast from multiple known fixed positions. The signal itself contains information about the difference between the DGPS stations received GPS position and it’s known exact position. These differences can be used to correct other GPS receivers that receive DGPS signal.

By using his RTL-SDR (with upconverter or HF modification) dewdude was able to receive the DGPS beacon in SDR#. Then by piping the output audio into SpectrumLab’s DGPS decoder he was able to decode the data contained within the DGPS signal. His post contains a tutorial showing how to set up SpectrumLab to decode DGPS. If you’re interested in hearing what a DGPS signal sounds like, dewdude has uploaded a sound sample at the bottom of another post of his.

Decoding Differential GPS (DGPS) signals in SpectrumLab
Decoding Differential GPS (DGPS) signals in SpectrumLab

Using a USRP E310 for Digital Video Downlink and Scanning on a Drone

Balint, one of the researchers at Ettus Research (the company behind the USRP range of software defined radios) has recently uploaded a video to YouTube showing one of his projects where he is prototyping the use of a digital signal for transmitting digital FPV video on a drone. The drone carries a USRP E310 SDR and transmits a QPSK video down developed in GNU Radio to a receiver on the ground.

FPV strands for “first person view” and is a growing hobby where remote controlled aircraft such as quadcopter drones are flown in first person view using live video from an on board camera.

Drone + SDR: USRP E310 real-time digital video downlink (teaser)

In another video balint also shows how the on board E310 can be used to transmit frequency scan FFT data via a WiFi link. This can be very useful for getting an antenna up high enough to get good reception for a scan.

Drone + SDR: USRP E310 airborne spectrum monitoring (teaser)

Visualizing the electromagnetic spectrum with Frequensea and an RTL-SDR

Over on YouTube user Frederik De Bleser has uploaded a video showing his new open source toolkit called Frequensea which can be used for visualizing the electromagnetic spectrum with an RTL-SDR or HackRF. The software allows you to visualize the output as an FFT spectrum in various 3D display modes and is even compatible with the Oculus Rift, a virtual reality headset.

Frequensea can be downloaded from https://github.com/fdb/frequensea, and it currently has installation instructions available for OSX, Ubuntu and the Raspberry Pi.

Visualizing the electromagnetic spectrum with Frequensea