Tagged: rtl-sdr

RSGB 2022: The UK Meteor Beacon Project

During last years Radio Society of Great Britain (RSGB) 2022 convention, Brian Coleman (G4NNS) presented a talk about the UK Meteor Beacon Project. The idea behind the project is to use a transmit beacon and a network of user-run receivers to help detect and study meteors. The talk has recently been uploaded to YouTube.

Radio signals can reflect off the meteor and the ionized trail left behind when it enters the atmosphere. This trail is highly RF reflective, so it can allow distant radio stations to be briefly received.

In the talk Brian explains the meteor detection, and explains the project in more detail.

The UK meteor beacon project is a collaborative project between the amateur radio and radio astronomy communities to collect data on meteor events over the UK. Phase I has been to establish a transmit beacon and Phase II is to create a network of receivers to monitor the radio echoes from meteors and stream data over the internet to support the study of meteor events and their impact on the ionosphere. Another key objective is to make possible a range of accessible radio-related STEM projects building on the interest in space and astronomy.

RSGB 2022 Convention presentation - The UK Meteor Beacon Project

TXAdvance: An RF Transmitter Manager Android App that uses RTL-SDR

Recently we came across a new RTL-SDR app on the Google Play store called TXAdvance which appears to be designed for professional sound engineers working in TV/film/stage/music production industry. The app uses an RTL-SDR to display the RF spectrum, helping sound engineers manage the RF spectrum for all their wireless sound recording devices, ensuring there is no overlapping signals, interference or intermodulation from other transmitters that could corrupt audio.

More information about the app can be found on their website at www.compasseur.com and the app itself can be purchased from the Google Play Store.

TXAdvance RTL-SDR Android App for Profressional Sound Engineers
TXAdvance RTL-SDR Android App for Professional Sound Engineers

Receiving TPMS Tire Pressure Data from a Mazda CX 5 with an RTL-SDR

Over on YouTube Robert from the Robert Research Radios channel has uplaoded a video showing how he has been using an RTL-SDR and rtl_433 to measure his Mazda CX5's wireless tire pressure sensors. The Mazda CX5 comes with TPMS tire pressure sensors in each tire, however when there is a low pressure warning, it does not actually tell you which tire in particular is low.

Robert used his RTL-SDR, rtl_433 and a custom script to read the wireless TPMS data coming from his tires and then matched the ID from each reading to the correct tire.

To go along with the video, Robert has uploaded a blog post explaining his setup and script.

RTLSDR Mazda CX 5 TPMS

An OpenWebRX fork with additional built in decoders

Thank you to Stefan for letting us know about a relatively modern OpenWebRX fork by luarvique that comes with additional built in decoders and features, such as SSTV, AIS, CW, RTTY, an MP3 recorder and SSTV image browser.

OpenWebRX is an open source web based SDR receiver program that allows you or others (if you allow them to), to access your SDR over the internet. It is compatible with KiwiSDR, RTL-SDR, Airspy, SDRPlay and many other software defined radio hardware. It was originally developed by Andras Retzler, but since abandoned by him, with a semi-official fork being maintained at openwebrx.de. However, other forks like luarvique can exist that implement a new set of features.

The full set of additions and improvements reads as follows:

This is the package repository for the improved version of the OpenWebRX online SDR. The new and original features available in this version of OpenWebRX:

  • Built-in SSTV decoder with background decoding.
  • Built-in AIS decoder.
  • Built-in CW decoder.
  • Built-in RTTY decoder.
  • Built-in MP3 recorder for received audio.
  • Image browser for received SSTV images.
  • Adjustable noise filtering based on spectral subtraction.
  • Adjustable tuning step.
  • Improved touch screen operation, with panning and zooming.
  • Improved scroll wheel support, with tuning and zooming.
  • Improved tuning in CW mode.
  • Bandpass filter adjustable with scroll wheel.
  • More reliable SDRPlay devices operation.
  • Better map information, with distances.
  • Better APRS map information, with weather.
  • Configurable session timeout, with a policy page.
  • HTTPS protocol support (requires SSL certificate).

The code comes packaged for Ubuntu 22.04 (amd64, arm64) and Debian 11 (amd64 arm64, armhf). There is also a ready to use Pi 4 SD card image available, linked on the GitHub readme. The original forked code can be found at https://github.com/luarvique/openwebrx.

According to discussion over on the OpenWebRX groups.io, the fork also runs on a Pi 3. In the image Neil Howard from the groups.io forum demonstrates an SSTV image he received with an SDRplay clone using the luarvique fork of OpenWebRX.

SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard
SSTV Image received by the luarvique fork of OpenWebRX. Credit: Neil Howard

Stefan also notes:

The maker of OpenWebRX+ Marek and also the maker of the original version of OpenWebRX Jakob are reachable via a Telegram channel: https://t.me/openwebrx_chat

Open Source Close Call Monitor for RTL-SDR

Thank you to Fabian for writing in and sharing with us his newly released RTL-SDR close call monitoring software called "rtl-sdr-close-call-monitor". The software is open source and written in Python. It's main purpose is to log any signal peaks that appear within a defined frequency range. Over on the GitHub Fabian explains the software:

These scripts use an RTL-SDR device to detect peak signals on a user specified frequency range. The scripts can also make an automatic blacklist so that different sources of RF noise won't cause continuous false positives. There are two scripts provided as examples. The scripts can be used to monitor certain frequencies for a wide range of purposes such as:

  • In criminal investigations, a close-call RF signal monitor can be used to detect and track communication signals used by criminals. This can help law enforcement agencies gather intelligence and evidence, and even prevent future crimes from being committed. By analyzing the frequency and strength of signals emitted by communication devices, a close-call RF signal monitor can provide valuable insights into the movements and activities of suspects, allowing investigators to piece together a timeline of events and make informed decisions about how to proceed with a case.
     
  • In military operations, a close-call RF signal monitor can be used to identify and track enemy communication signals, providing valuable intelligence for strategic decision-making.
     
  • In scientific research, a close-call RF signal monitor can be used to collect and analyze data related to wireless communication systems, providing valuable insights for thesis projects and other research studies.
An excerpt of Fabian's close call monitoring Python code.

Hunting for Space Radio Pirates on the US Military Fleet Satcom Satellites

In the 70's and 80's the US government launched a fleet of satellites called "FLTSATCOM", which were simple radio repeaters up in geostationary orbit. This allowed the US military to easily communicate with each other all over the world. However, the technology of the time could not implement encryption. So security relied entirely on only the US militaries technological advantage at being the only ones to have radio equipment that could reach these satellites.

Of course as time progressed equipment which could reach the 243 - 270 MHz range of the satellites became common place, and the satellites began picking and repeating terrestrial broadcasts of things like cordless phones. These days the satellites are often hijacked by Brazilian radio pirates, who use the satellites for long range communications.

A common hobby of RTL-SDR users is to listen to these pirates. All you need is a simple antenna and to be based in a region where the satellites cover both your ground station and the pirates.

Over on YouTube the "saveitforparts" channel has uploaded an entertaining video overviewing the pirate phenomenon, and showing how it's possible to listen in using a cheap Baogeng scanner and RTL-SDR. He uses a homemade Yagi and cleverly makes use of an old security camera motorized PTZ mount to accurately aim the antenna. Once the Yagi antenna is aimed at the satellite, pirates can be heard on the radio.

Searching For Space Pirates On Old Military Satellites

On a previous post, we showed an interview by SignalsEverywhere and an anonymous Brazilian radio pirate who explains how and why they do what they do. If you search our blog for 'satcom' you'll also find several previous posts including examples of receiving SSTV from pirates.

Visualizing RF Fields in Augmented Reality with a tinySA-Ultra or RTL-SDR and Android Smartphone

The tinySA-Ultra is an affordable handheld spectrum analyzer that can be purchased for around US$130 on Aliexpress and authorized resellers such as R&L Electronics in the USA.

Recently on YouTube Manahiyo has used his tinySA-Ultra, and combined it with an RF EMC probe and an Android smartphone to create an augmented reality RF display. This is useful for measuring and visualizing the RF power around electronic devices for example. The code is entirely open source and released on GitHub. 

Manahiyo has also released an identical version that works with RTL-SDR dongles on GitHub as well.

In the past we've also posted about Manahiyo's previous work, in which he implemented a very similar augmented reality project using an RTL-SDR.

Augmented Reality EMC Probe with a tinySA-Ultra
[RadioFieldAR -tinySA-] Visualize radio wave strength.

Listening in on Hollywood Reality TV Show Wireless Microphones with an RTL-SDR

Over on Reddit user u/mknlsn has posted an interesting use for his RTL-SDR. He happens to live next door to a Hollywoood reality TV show production and was able to use his RTL-SDR to listen in on the wireless microphones fitted to the cast. The wireless microphones used by the production appear to be simple analogue FM modulated, without any sort of security.

We remind readers to check local laws on this sort of use, especially if recording audio, as some countries and US states may have differing laws on what can be recorded, or even listened to live. This would likely be considered private communications, so recording and sharing would definitely be illegal in most regions. 

Recently we also posted about Frugal Radio using an Airspy SDR to listen in on wireless microphones from outside a theatre show.

Wireless microphones picked up by RTL-SDR