Category: RTL-SDR

Marine Vessel AIS and AirNav ShipXplorer

AirNav systems are a company that run radarbox.com, one of the big ADS-B aggregation tracking sites for tracking aircraft around the world. They also run a similar platform called ShipXplorer for tracking marine vessels using AIS data. The team at AirNav have provided us with a nice explanation of what AIS is and how it works. They note that they also sell a modified RTL-SDR with AIS filters and an LNA built in.

Presumably AirNav are seeking feeder volunteers for their ShipXplorer service with the submission of this post. We receive no compensation for this post and do not endorse one aggregator over another.

Below is the text from AirNav:

How Does the Automatic Identification System (AIS) Work

Introduction

Automatic Identification System (AIS) is a crucial technology used for monitoring and tracking the movements of vessels at sea. It has become an essential tool for ensuring maritime safety, security, and efficiency. In this blog post, we will explore how AIS vessel tracking works, its benefits, limitations, and future prospects.

How Does AIS Vessel Tracking Work?

AIS is an automatic tracking system that uses transceivers installed on ships to transmit vital information such as position, speed, course, name, call sign, type of ship, and destination. This data is then received by terrestrial or satellite-based AIS receivers and transmitted to various stakeholders, including shore-based authorities, other ships, and online platforms. The information is displayed in real-time, allowing users to monitor the movement of vessels with pinpoint accuracy.

There are two types of AIS messages: Class A and Class B. Class A messages are mandatory for all ships over 300 gross tons, while Class B messages are optional but recommended for smaller vessels. Class A messages have a higher transmission power and update rate than Class B messages, making them more reliable for long-range detection.

AIS operates principally on two dedicated frequencies or VHF channels: AIS 1: Works on 161.975 MHz- Channel 87B (Simplex, for the ship to ship) AIS 2: 162.025 MHz- Channel 88B (Duplex for the ship to shore), which provide a range of up to 20 nautical miles for terrestrial stations and up to 1,000 nautical miles for satellite systems. The system uses Time Division Multiple Access (TDMA) technology to avoid signal collisions and ensure seamless communication between multiple vessels and base stations.

Benefits of AIS Vessel Tracking

AIS vessel tracking offers numerous benefits, including enhanced safety, improved operational efficiency, and better decision-making capabilities. Some of these benefits include:

  1. Improved Collision Avoidance
    By providing accurate information about a vessel's location, speed, and direction, AIS helps prevent collisions and reduces the risk of accidents. Ships can use this information to maintain safe distances from each other and navigate crowded waterways safely.
  2. Increased Efficiency
    AIS enables ships to optimize their routes and fuel consumption, leading to increased efficiency and cost savings. By sharing their positions and intentions, vessels can coordinate their movements and avoid wasting time and resources on unnecessary maneuvers.
  3. Enhanced Search and Rescue Operations
    In case of emergencies, AIS provides critical information that helps search and rescue teams locate and assist distressed vessels quickly. The real-time data provided by AIS allows responders to make informed decisions and allocate resources effectively.
  4. Better Decision Making
    AIS data can be integrated with other systems, such as weather forecasting tools, to help shipping companies make informed decisions about their operations. For example, they can adjust their schedules based on predicted weather conditions or reroute their vessels to avoid congested areas.

Limitations of AIS Vessel Tracking

While AIS vessel tracking is a powerful tool, it does have some limitations. These include:

  1. Limited Coverage
    Although AIS signals can travel up to 20 nautical miles via terrestrial stations, this coverage may not be sufficient in remote or offshore areas where there are no base stations. Satellite-based AIS systems address this limitation but come at a higher cost.
  2. Potential Security Risks
    Since AIS transmissions are unencrypted, there is a potential risk of interception and misuse by malicious actors. However, measures such as frequency hopping and encryption can mitigate these risks.

Future Prospects of AIS Vessel Tracking

As technology advances, AIS vessel tracking is expected to evolve and offer even greater benefits.

  1. Integration with Autonomous Shipping
    Autonomous ships rely heavily on sensor data for navigation and collision avoidance. AIS integration with autonomous shipping systems could enhance situational awareness and improve overall safety.
  2. Real-Time Cargo Monitoring
    AIS could be used to track individual cargo containers in real-time, enabling logistics companies to monitor their shipments more accurately and efficiently.
  3. Environmental Monitoring
    AIS-equipped vessels could collect environmental data, such as water temperature, salinity, and pollution levels, helping researchers and policymakers better understand and manage marine ecosystems.

Conclusion

AIS vessel tracking is an indispensable tool for enhancing maritime safety, security, and efficiency. While it has some limitations, advancements in technology continue to expand its capabilities and applications. As shipping becomes increasingly digitalized, AIS will remain a cornerstone of maritime communications and surveillance.

The SHipXplorer AIS Optimized RTL-SDR

SatDump V1.1.4 Released

SatDump is a popular program used to receive and decode images and other data from various weather satellites. SatDump works great RTL-SDR Blog dongles and with our Discovery Dish, an easy to use dish and feed for receiving L-band and other weather satellites. Recently the author of SatDump released version 1.1.4 which brings several new features including:

  • Autotrack/Scheduler improvements - multi mode has been added which allows all pipelines to run, even if more than one satellite is overhead at the same time. This is useful for NOAA and METEOR satellites at 137 MHz as there can often be more than one active satellite broadcasting images at different frequencies during a pass.
  • TUBIN Raw/Video Mode
  • ESA Cluster support
  • Additional Pipelines - Including Peregine X-Band TLM, the IM-1 Moon Mission and PRETTY S-band dump.
  • Themes - Choose between Dark, Light, Phosphor and Win98 themes.
  • Android Improvements - Blog V4 support added on Android, OpenCL support added.
  • Added composites - Various composite image products added to various satellites. Including Fog, panchromatic, ice detecting and more.
  • Other Features - support for M1 Mac builds added and various other fixes.
  • Bug Fixes - Memory leaks fixed and various bug fixes including a bug that caused problems with RTL-SDR devices on low power hardware like Raspberry Pi's and Orange Pi's.

If you enjoy SatDump consider donating to the main author at ko-fi.com/aang23.

SatDump Multi-Mode Feature. Receiving data from multiple 137 MHz satellites at the same time.

WarDragon Passive Radar with Blah2 and ADS-B Delay-Doppler Truth

Over on his YouTube channel, Aaron, creator of DragonOS and the WarDragon kit has uploaded a video showing the Blah2 passive radar software working with an SDRplay RSPDuo. In the video Aaron shows some setup steps before showing the passive radar range-doppler graph.

Blah2 is passive radar software that appears to be inspired by the KrakenSDR passive software that was removed for regulatory reasons. We note that it is legal for others to publish open source passive radar software, but KrakenSDR cannot legally publish their own open source passive radar software because it would be tied to their own physical product. Providing code would mean they essentially sell an off the shelf passive radar product which is restricted.

The notes in Blah2 specifiy that it currently only supports the SDRplay RSPduo and USRP devices, but in the future they are looking to add support for the KrakenSDR and modified RTL-SDR and HackRF hardware.

Aaron also briefly demonstrated the related adsbdd software, from the same author as Blah2. This software allows a user to convert ADS-B data to delay-doppler truth. Essentially allowing you to confirm is an aircraft position determined via ADS-B is on the range-doppler ellipse determined via passive radar. In the future the author hopes to be able to plot all aircraft in a 2D delay-doppler space graph. 

DragonOS FocalX Passive Radar Setup + Test w/ Open Source Code (RSPDUO, RTLSDR, Blah2)

Windows Binary of GQRX Released

Gqrx has long been one of the most commonly used pieces of software defined radio software for Linux and MacOS. However, it has never had a Windows release until just two days ago when the team released an experimental Windows binary.

We gave the new Windows binary a test with our RTL-SDR Blog V4 and everything works just fine. If you want to give it a go, just be aware that Chrome and many antivirus programs will flag the zip as suspicious. However, this is just a false positive, since this is the first release and the file doesn't have a long history on the web.

To download it, go to the Gqrx releases page on Github, and download the latest Gqrx-2.17.4-Windows.zip file from under Assets.

GQRX now on Windows
GQRX now on Windows

Canada Moves to Ban Flipper Zero and Possibly Software Defined Radios

Dominic LeBlanc, Canada's Minister of Public safety has recently declared that they plan to ban devices "used to steal vehicles by copying the wireless signals for remote keyless entry, such as the Flipper Zero". The text specifically calls out the Flipper Zero, however the wording appears to imply that any device that can copy a signal will be banned. This means the ban could extend to RX/TX SDRs like the HackRF and possibly even RX only SDRs like RTL-SDRs.

The Flipper Zero is an affordable handheld RF device for pentesters and hackers. It is not based on SDR technology, however it uses a CC1101 chip, a digitally controlled RX/TX radio that is capable of demodulating and modulating many common digital modulations such as OOK/ASK/FSK/GFSK/MSK at frequencies below 1 GHz. There are many CC1101 devices on the market, but the Flipper Zero has gained huge popularity on social media because of it's excellent software support, as well as its cute marketing tactic. In the past it was even featured on the popular Linus Tech Tips YouTube channel.

Flipper Zero has had a long line of setbacks including PayPal freezing 1.3M of its cash, and US customs temporarily seizing its shipments, then passing a $70,000 bill on to them for storage fees and Amazon banning the product on their marketplace.

In our opinion, we believe that the ban appears to be misguided. The Flipper Zero is a basic device that can only perform a simple replay attack, which is to record a signal, and replay it at a later time. These sorts of attacks do not work on vehicles built after the 90's which now use rolling codes or more sophisticated security measures. To defeat rolling code security, a more sophisticated attack called Rolljam can be used. A Rolljam device can be built for $30 out of an Arduino and two cheap transceiver modules.

However, according to arstechnica the biggest cause for concern in terms of car theft is a different sort of attack called "signal amplification relay".

The most prevalent form of electronics-assisted car theft these days, for instance, uses what are known as signal amplification relay devices against keyless ignition and entry systems. This form of hack works by holding one device near a key fob and a second device near the vehicle the fob works with. In the most typical scenario, the fob is located on a shelf near a locked front door, and the car is several dozen feet away in a driveway. By placing one device near the front door and another one next to the car, the hack beams the radio signals necessary to unlock and start the device.

This sort of attack is a lot less sophisticated in many ways as all you are doing is amplifying a signal, and no clever hardware like the Flipper Zero or a software defined radio is even required. The X video below demonstrates such a hack where a criminal holds up a loop antenna to a house. The loop antenna is connected to a signal amplifier which amplifies the keyfob signal, tricking the car into thinking the keyfob is nearby, and allowing the door to be unlocked by touching the handle, and then turned on with the push to start button.

Flipper zero note that they have not been consulted about the ban, and replied on X stating that they are not aware of the Flipper Zero being used for car theft.

A Low Cost P25 Police Scanner with RTL-SDR, Raspberry Pi 5 and SDRTrunk

Thank you to Mike for writing in and sharing with us his video detailing how he makes use of a Raspberry Pi 5, touch LCD Screen and RTL-SDR to create a portable and low cost P25 police scanner. Mike notes that the cost of his system is $250, which is a lot cheaper than a comparable $600 P25 scanner. 

Here is my latest weekend project; a Raspberry Pi 5 with an RTL-SDR dongle running SDRTrunk software. It is configured to listen to the local LAPD channels and runs great! The chip gets a bit hot so I think I need to add a fan.

Building a $600 P25 Police Scanner for $250!!! (SDR-Pi)

Taylor Swift Threatens Legal Action Against Owner of X Account that Tracks her Private Jet via ADS-B

Jack Sweeney is a student who operates various social media and websites dedicated to tracking the private jets of celebrities and notable persons. In the past he's drawn the ire of Elon Musk who banned his @ElonJet account in 2022 which used to provide live updates on the location of Elon Musk's private jet. These days he operates the @ElonJetNextDay account which tracks Elon's jet with a 24 hour delay on X, but continues to track the jet live on other platforms.

Recently the legal team for global superstar Taylor Swift threatened legal action against Jack Sweeney for running the various social media accounts that track her private jet including @SwiftJetNextDay on X with a 24 hour delay, or live on alternative platforms like Mastodon. Swift's legal team claim Sweeney's live tracking accounts pose an “imminent threat to the safety and wellbeing” of Swift.

Jack notes that he makes use of legal live ADS-B flight data from public data aggregators like Airplanes.live and AirFramesIO. ADS-B data is most commonly provided from contributors with RTL-SDR dongles running on Raspberry Pi single board computers. 

Even without Sweeney's social media accounts anyone can legally look up this live public flight data data, or even receive it themselves directly from the aircraft if they are close enough. Although a point can be argued that the social media accounts run by Sweeney make it significantly easier for this information to be obtained and shared by anyone.

An example notification from @SwiftJetNextDay for Taylor Swift's private jet flight.

FOSDEM 2024 Videos now Available: Synthetic Aperture WiFi RADAR, GPU DSP Acceleration and more

FOSDEM (Free and Open Source Developer’s Meeting) is a yearly conference that took place in Brussels, Belgium on 3 - 4 February 2024. This conference featured a room on Software Defined Radio and Amateur Radio.

Recently the videos of most the talks have been uploaded to their website. Some interesting talks include:

Covert Ground Based Synthetic Aperture RADAR using a WiFi emitter and SDR receiver

Link to Talk Page

Using a WiFi emitter as radiofrequency source illuminating a scene under investigation for slow movement (e.g. landslides), a Ground-Based Synthetic Aperture RADAR (GB-SAR) is assembled using commercial, off the shelf hardware. The dual-channel coherent Software Defined Radio (SDR) receiver records the non-cooperative emitter signal as well as the signal received by a surveillance antenna facing the scene. Spatial diversity for azimuth mapping using direction of arrival measurement is achieved by moving the transmitter and receiver setup on a rail along a meter-long path -- the longer the better the azimuth resolution -- with quarter wavelength steps. The fully embedded application runs on a Raspberry Pi 4 single board computer executing GNU Radio on a Buildroot-generated GNU/Linux operating system. All development files are available at https://github.com/jmfriedt/SDR-GB-SAR/

Synthetic Aperture RADAR with WiFi and USRP SDR

Using GPU for real-time SDR Signal processing

Link to Talk Page

GPU processors have become essential for image or AI processing. Can they bring anything to real-time signal processing for SDR applications? The answer is yes, of course, but not all classic algorithms (FIR, DDC, etc.) can be used "as is", sometimes a different approach must be taken. In this presentation, I will share the solutions that I implemented to achieve multi-channel DDC on NVIDIA Jetson GPU and will make a comparison with "classic CPU" approaches.

Using GPU's for Real Time Signal Processing

Maia SDR: an open-source FPGA-based project for AD936x+Zynq radios

Link to Talk Page

Maia SDR is an open-source project with the main goal of promoting FPGA development for SDR and increasing the collaboration between the open-source SDR and FPGA communities. Currently it provides a firmware image for the ADALM Pluto and other radios based on the AD936x and Zynq. This firmware can display a real-time waterfall at up to 61.44 Msps in a WebSDR-like interface using WebGL2 rendering, and record IQ data in SigMF format in the SDR DDR. The FPGA design is implemented in Amaranth, an Python-based HDL, and the software stack is implemented in Rust, targetting the embedded ARM CPU and WebAssembly.

The first firmware version was released in February 2023, and the project was presented in June in the Software Defined Radio Academy. In this talk we cover the progress since the summer, including the addition of support for devices such as the Pluto+ and AntSDR. We focus on the technical details of the project and the possibilities for re-using some of the components in other projects.

Maia SDR

DAPNET: Bringing pagers back to the 21st Century

Link to Talk Page

When talking about pagers, most of us will think about an object of the past, often seen in TV shows from the 90s, used by medical staff and businessmen. However, they're an interesting way to get simple data broadcast over amateur radio frequencies, with receivers that can be built for less than 20€. We'll explore this and understand how an extensive network can be deployed with simple equipment and using open source hardware and software.

DAPNET Talk