Category: Applications

Receiving and Decoding Tire Pressure Monitor Systems using an RTL-SDR

Tire Pressure Monitoring Systems (TPMS) are comprised of sensors that are designed to measure the tire pressures on a vehicle and then wirelessly transmit the data to a monitoring computer, which will then alert the driver when the tire pressure is incorrectly set.

At the Toorcon conference, Jared Boon has given a talk showing how he used an RTL-SDR and a GNU Radio program that he developed to reverse engineer the TPMS wireless protocol, and read the data that is sent. Jarod also notes that TPMS is potentially a security risk that could be used to track cars. The talk has been uploaded to YouTube and is shown below.

Reversing Tire Pressure Monitors with a Software-Defined Radio

HDSDR Updated to Version 2.70. Now with Autocorrelation Feature for Signal Identification

HDSDR, a popular SDR program used with the RTL-SDR dongle has been updated to version 2.70. The new features include

– better CPU utilization
– added Automatic Notch Filter
– added AFC for AM and FM. AFC can be deactivated in ECSS mode
– smoothed S-Meter display
– enhanced parameters for ‘SDR on IF output’
– new keyboard shortcuts for Lo/HiCut and WAV files
– ‘spectrum’ switchable to Autocorrelation/Cepstrum display (Click on ‘Spectrum’ label)
– TX-Button for HRD(DDE) / CAT to HDSDR
– added ‘Double Size’ option in Frequency Input Dialog
– Frequency Manager now provides 5 User Banks

The new autocorrelation feature is particularly useful for signal identification. The authors of HDSDR have created a webpage showing what the autocorrelation feature can be used for, and how to use it.

HDSDR Autocorrelation Feature
HDSDR Autocorrelation Feature

rtl_udp: Fork of rtl_fm with UDP controls

Over on our forums, user sysrun has posted about his fork of the rtl_fm command line tool. His fork allows retuning of the rtl_fm program via UDP without the need to restart the program. In the future he hopes to support UDP PCM streaming. He writes

rtl_udp is a copy of rtl_fm with a special feature: It opens a udp control port (currently fixed to 6020) which takes commands like changing the frequency or mode. No need to restart :)

Credits, Idea & original Code by olgierd (http://qi.reddit.com/user/olgierd)

Usage:
python script udpclient.py for easy operation included.

possible commands:

  • freq (./udpclient.py freq 101900000)
  • mode (./udpclient.py mode 0 (for fm))
    0 = FM
    1 = AM
    2 = USB
    3 = LSB
  • squelch (./udpclient.py squelch 0)
    0 = OFF
    n = Value
  • gain (./udpclient.py agc auto)
    auto = Automatic
    n = Gainvalue; 195 = 19.5db
  • agc (./udpclient.py agc 1)
    0 = OFF
    1 = ON

SDRTouch Version 1.7 Released

The Android based SDR program SDRTouch has been officially updated to version 1.7. News comes via this forum post. This looks to be a major update which significantly improves audio quality and performance. The new features are listed below.

  • FM is now in STEREO
  • New audio recording feature for PRO users
  • Improved reception and audio quality. All filters were tested for quality and all bugs discovered were removed.
  • The multi-threading logic was completely rewritten. Now it’s faster than ever before.
  • Audio is now using NDK.
  • PPM correction, audio gain setting
  • A lot of bug fixes and UI enhancements
  • Experimental x86 support
sdtouch
SDR Touch Screenshot

Funcube SDR Radio Telescope

A Radio Astronomer by the name of Dr David Morgan has released a tutorial/paper he wrote detailing how he uses the Funcube dongle Pro+ as a tool for radio astronomy. The Funcube dongle Pro+ is a software defined radio similar to the RTL-SDR, with higher cost, but better performance in some areas.

Dr Morgan uses his Funcube dongle with the SpectrumLab Windows software, which is a specialized audio analyzer. For the hardware, David uses a 3m focal plane dish antenna and a 1200 MHz high pass filter.

The paper goes into good detail about some of the technical side of radio astronomy, shows how to calibrate the telescope using the sun and also shows several measurements made. We note that the same procedures could also likely be done with the RTL-SDR.

Signal Intensity during Drift Scan through Cygnus Spiral Arm
Signal Intensity during Drift Scan through Cygnus Spiral Arm

Receiving, Decoding and Decrypting GSM with the RTL-SDR : YouTube Talk and Slides

A few days ago we posted about how Domi aka Domonkos Tomcsányi wrote on his blog about decoding and decrypting GSM signals from your own cell phones. Domi also did a talk at the CampZero conference which has now been uploaded to YouTube. His slides can be obtained from this link.

CampZer0 // Domonkos Tomcsányi: GSM - have we overslept the last wake-up call?

RTL-SDR Spectrometer for a Small Radio Telescope

Marc Higginson-Rollins of the University of Kentucky has published an academic styled paper in conjuction with Dr. Alan E.E. Rogers of the MIT Haystack Observatory showing how they used an RTL-SDR to implement a Small Radio Telescope (SRT).

In the paper they discuss how they dealt with the frequency drifting and offset problems common in the RTL-SDR. They also show how they dealt with the center spur by correcting the bias that it introduced and how they filtered out RFI noise from a nearby radar station and electronics.

Using the RTL-SDR and SRT they were able to measure the spectra of several well known regions of neutral hydrogen emissions, and measure the galactic rotation curve shown below.

Galactic Rotation Measurements with the SRT
Galactic Rotation Measurements with the SRT and RTL-SDR

Wavesink Plus: Android RTL-SDR App with FM+RDS/DAB+/DRM+ Decoding

Wavesink Plus, the paid version of the trial version of Wavesink has been released on Google Play. Wavesink Plus is an Android app which has FM+RDS, DAB+ and DRM+ receiving and decoding capabilities when connected to an RTL-SDR dongle via a USB OTG cable.

We gave Wavesink Plus a test today on a HTC One X Android phone and were pleased to discover that it works perfectly. The user interface has been tidied up from previous versions, and DAB+ has been added. There is now also auto tuning functionality, which will automatically find a station.

In further testing we found that the latest version of Wavesink was fast and snappy and was able to load DAB+ stations quickly, and decode them with clear audio. FM radio also sounded clear and RDS information loaded quickly as well.

Download the trial version here and buy the full version from this link.

Wavesink Plus Decoding DAB+
Wavesink Plus Decoding DAB+