Category: Applications

DragonOS: Decoding Train Telemetry with SoftEOT and RTL-SDR

Over on his YouTube channel Aaron who created and maintains the DragonOS SDR Linux distribution, has uploaded a video demonstrating how to use an RTL-SDR and SoftEOT/PyEOT to decode North American wireless train telemetry.

HOT (Head of Train), EOT (End of Train) and DPU (Distributed Power Unit) telemetry is sent from various parts of a train and contains information about things like voltages, brake line pressure and to monitor for accidental separation of the train.

In his video Aaron uses his DragonOS Linux distribution, SDR++ with an RTL-SDR Blog V4 dongle and the SoftEOT and SoftDPU decoders. SoftEOT and SoftDPU are both Windows programs, however Aaron shows how to use WINE to run them in Windows. Later he shows how to use an alterative decoder called PyEOT which is based on GNU Radio.

DragonOS FocalX Decoding Train Telemetry w/ SoftEOT/PyEOT (RTLSDR V4, WINE AppImage, GR 3.10)

Receiving 2.2 GHz with the RTL-SDR and Nooelec Ham It Down

Over on his YouTube channel dereksgc has uploaded a new video where he tests out a new yet to be released downconverter product from NooElec. A downconverter works by shifting high frequencies down into a range that can be received by the RTL-SDR. This makes it useful for receiving 2.2 GHz S-band satellite downlinks which is out of the tuning range of RTL-SDR dongles.

In his video dereksgc shows the new 'Ham-it-down' downconverter, and tests it with an LNA and S-band helix feed and dish. He shows that he is able to easily receive S-band telecommunications satellites without a dish, and with a dish he is able to receive the Coriolis and Chandrayaan-3 satellites.

The ham-it-down is expected to cost US$90 when released. We note that a much lower cost solution might be a commercial 2.2 GHz MMDS downconverter which also comes built in with an LNA and filtering and can be obtained from Aliexpress for less than US$20. Alternatively, the $90 might be better put towards a HackRF clone which is almost the same price and can receive S-band natively without the need for external downconverter.

KrakenSDR: Finding Multiple GSM Base Station Transmit Towers with the Multi-VFO Feature

If you weren't already aware, KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding. KrakenSDR is in stock and can be purchased from CrowdSupply or Mouser. More information is also available on our website at krakenrf.com.

Last month we used the KrakenSDR to find the location of a low power FM transmitter. Now in this video we're using KrakenSDR to find the location of GSM base station transmit towers for four frequencies. We're also using the multi-vfo feature to capture the bearing data of these four frequencies simultaneously which can save us some search time.

Once we've found the first transmit tower, we already have some logged bearing data that can be used to help us find the second tower faster. Then the third and fourth towers are even faster to find due to even more data having already been collected.

Interestingly, it also turns out that the first frequency we search for is actually being used by another tower that we pass along the way back. The location of this tower was picked up on the drive back to the first tower. It's possible that these two towers which are a few kilometers apart are covering different areas with directional antennas.

Also note that the first two transmitter searches use the "auto-zoom" map camera feature, which will automatically zoom the screen to show both the vehicle and estimated transmitter location. The second half uses the standard free camera mode.

This is on a new build of the App which is currently in testing, so some things may look slightly different to the currently released version. The new app version will have some minor feature improvements.

KrakenSDR: Finding Multiple GSM Base Station Transmit Towers with the Multi-VFO Feature

 

Fox Hunting with the KrakenSDR

Over on his YouTube channel Mark Jessop has uploaded some dash cam footage showing him using a KrakenSDR and a custom LED display to hunt down three amateur radio transmitters during a fox-hunt.

An amateur radio fox-hunt is an activity where someone will hide a transmitter within a defined area, and it is up to the hunters to use radio direction finding equipment to find it. The KrakenSDR is our 5-channel coherent radio based on RTL-SDRs, and it can be used for applications like radio direction finding.

Mark uses a custom four element array on the roof of his car, which is connected to his KrakenSDR. Instead of the KrakenSDR app, Mark prefers to use his custom LED HUD to displays the bearings and signal power directly.

Some annotated and sped-up dash-cam footage captured during the July 2023 Amateur Radio Experimenters Group Fox-hunt. We run these monthly, and usually have three transmitters hidden around the Adelaide (South Australia) area.

I run a KrakenSDR with a custom-built 4-element antenna array mounted to the roof of my car. This gives me direction estimates to the target transmitter, at least when the signals are strong enough!

I've also build a heads-up-display which helps me safely make use of the KrakenSDR's output data while driving. The source code for this is here: https://github.com/darksidelemm/neopixel-doa-display

The display is shielded so it's not visible from outside the car - Red & Blue lights on your dashboard can give the wrong impression!

AREG Fox-hunt - 14th July 2023

Goestools Now Ported to Run on Windows

Thank you to Carl Reinemann (aka USRadioGuy) for letting us know through his blog post that goestools has recently been ported to Windows. Goestools is a software package that is used to receive and decode images from GOES weather satellites. In the past it was only available for Linux systems, however recently thanks to the work of Jamie Vital, goestools has now been ported and can run on Windows. Carl Reinemann has confirmed that the software runs perfectly on Windows. Our GOES tutorial should also be easily modified to work with the Windows port.

The Windows port can be downloaded from goestools-win on GitHub. If you are interested, Jamie Vital is also the author of Vitality GOES, which is a program that can display the received weather images in a nice GUI.

Alternatively we note that another cross platform GOES decoder is SatDump which is currently the most popular choice for GOES.

Goestools on Windows

TechMinds: Detecting Bats with an Ultrasonic Sensor and Software Defined Radio

Back in 2018 we posted about someone who had combined an ultrasonic piezo speaker and an SDRPlay RSP1A in order to create a device that can detect the ultrasonic sonar sound from bats.

Recently on YouTube Matt from the TechMinds YouTube channel was able to create a similar system using a MEMS microphone from Knowles which can receive audio in the 100 Hz ~ 80 kHz range. He connects the microphone to a 3.3V supply and connects the output of the microphone to his SDRplay RSPDx.

The system was then able to successfully hear the sound of bat sonar at his home location in the UK.

Ultrasonic BAT Detector Using Software Defined Radio

Receiving Unintentional Voice Transmissions from GPS Satellites

Over on dereksgc's YouTube channel we've discovered a few more recent interesting videos from his satellite decoding series that people may be interested in. One from two weeks ago shows how it's possible to receive voice transmissions on navigation satellites such as GPS.

Many navigational and meteorological satellites carry a search and rescue (SAR) repeater which is intended to receive UHF emergency locator beacons and rebroadcast them in the L-band or higher. However the repeaters appear to be picking up all sorts of other signals from the ground, including voice transmissions. Dereksgc notes that the theory is that there are some land based communications systems in some countries that are sharing frequencies that emergency locator beacons use, or that malicious pirates may be actively using these SAR repeaters for their own communications.

Dereksgc shows examples of retransmitted signals on the Beidou, GLONASS and Elektro-L satellite downlinks at 1.5442 GHz and at 2.226 MHz for the GPS satellites. He also shows what sort of satellite dish and feed setup you need. In the video he uses a HackRF as the SDR, but you could also use an RTL-SDR for the satellites that transmit at 1.5442 GHz.

Receiving voice transmissions from GPS satellites || Satellite reception pt.10

André shares his QO-100 Ground Station and HF/VHF/UHF Station

Thank you to RTL-SDR.com reader André for submitting and sharing with us his QO-100 ground station setup. The setup also includes antennas and equipment to receive HF and VHF/UHF. His setup can serve as an example of a well set up permanent installation.

André's set up consists of a 1.8 meter prime focus dish, Raspberry Pi 4, GPIO connected relay, Airspy R2, Ham-it-up upconverter, coaxial relay for switching between Mini-Whip and Discone Antenna, and FM bandstop filter and a power terminal rail block. The Airspy R2 is used for HF/UHF/UHF reception and the antennas and upconverter are all controlled via a web connected relay system. All equipment is enclosed in an outdoor rated box, and André notes everything has been working well from temperatures range from -10C to 35C.

Inside the satellite dish feed is housed an Adalm Pluto SDR, and a wideband LNA and a USB to LAN converter with power over Ethernet. A small log periodic Yagi serves as the feed. In order to work the wideband DATV band on Qo-100, André' swaps out this feed for a custom feed and brings the PlutoSDR indoors where it is connected to a 120W Spectran Amplifier and modulator.

For the full writeup of his setup, we have uploaded André's document here.

André's ground station setup for QO-100 and HF/VHF/UHF