Last month we posted about Aaron's video on Meshtastic, and how it's possible to decode the Meshtastic protocol using an RTL-SDR and GNU Radio project called Meshtastic_SDR. 

If you weren't aware, Meshtastic is software that enables off-grid mesh network based communications and can run on cheap LoRa hardware. The mesh based nature of the system means that communications can be received over long distances, without any infrastructure, as long as there are sufficient Meshtastic nodes in an area that can route the message to the destination node. One example application of Meshtastic is to use it as a mesh-based text messaging system. This might be useful for teams of hikers, pilots, or skiers who operate in remote areas without cell phone coverage.

In his latest video, Aaron shows how Meshtatsic_SDR can also be used to transmit the Meshtastic Protocol using a transmit capable SDR like the HackRF. Aaron writes in the video description:

In this video, we take a deeper dive into the setup and usage of the meshtastic_SDR repository, which now enables the transmission and reception of Meshtastic using Software Defined Radios (SDRs). Recent updates have made this possible by partially leveraging GNU Radio flow graphs for both RX (receive) and TX (transmit), and integrating Python scripts that connect to ZMQ sources for message input and ZMQ outputs for message decoding.

I demonstrate the setup using a HackRF for the transmit side and an Airspy R2 for receiving. We also verify the results of TX and RX using a standard Meshtastic receiver to ensure accurate performance.

Over on YouTube Paul Lutus has recently posted a video that is a great introduction to software-defined radio, RTL-SDR, and some of the various signals that can be received with one. In the video he uses an RTL-SDR Blog V4, which has a built-in upconverter, allowing for good reception of HF signals.

Paul's video briefly explores SDR theory, before demonstrating various signals on both the HF and VHF+UHF bands that can be received with an RTL-SDR Blog V4. He also briefly touches on GNU Radio.

If you are a just getting started with RTL-SDR this might be a good overview video to watch. Paul has also set up a companion webpage for the video that outlines some of the software installation and usage steps mentioned in the video in greater detail.

Over on her YouTube channel SignalsEverywhere, Sarah has uploaded her latest video showing how it is possible to monitor Itron ERT smart meters on an Android device.  Smart meters are used to wirelessly monitor the usage of residential utilities such as water, gas, and electricity. With an RTL-SDR and some decoding software, it is possible to monitor the data coming from your own and your neighbours meters (at least for certain brands of meter).

In her video, Sarah shows how she compiled the rtl_amr decoder software for Android, and created her own Android app called "AndAMR" for displaying the data decoded by rtl_amr. The rest of the video shows how to set up and use the app.

In his latest video, Matt from the TechMinds YouTube channel tests out an LHCP L-band helix feed designed for receiving Inmarsat satellites. Matt pairs the feed with an 85cm satellite dish, an L-band LNA, and an Airspy Mini.

The L-band helix feed comes from a small German engineering company called nolle.engineering. The feed is priced at 94.70 Euros (incl. VAT) (~$102 USD), plus shipping costs. It is a passive antenna so it needs to be combined with an LNA to be usable with a typical SDR.

In the video Matt shows that the reception with the LHCP helix + dish setup is better than expected. He also compares it to a previous test he did with a longer RHCP helix antenna also produced by nolle.engineering. The RHCP antenna is used to be used without a dish, however, as expected the SNR is less than the dish + small LHCP feed setup. Matt then shows some Inmarsat signals being decoded including STD-C and Aero voice.

On June 25 the NOAA GOES-U weather satellite was successfully launched on a SpaceX Falcon 9 Heavy rocket. Once it reaches geostationary orbit, this will be a new weather satellite that RTL-SDR hobbyists can receive with an RTL-SDR dongle, satellite dish, and LNA.

From launch, it will take about two weeks for GOES-U to reach geostationary orbit and once it gets there it will be renamed to GOES-19. It is due to be positioned where GOES-16 currently is, and GOES-16 will become the redundant backup satellite. This positioning will make the satellite visible to those in North and South America.

We are anxiously looking forward to the first images from GOES-19 received by hobbyists, but once positioned it will probably take several weeks to be tested and calibrated before hobbyists can receive any signals on L-band. 

Over on X, @WeatherWorks posted a short video showing that the launch plume was visible from GOES-16.

The @CIRA_CSU account has also posted a video from GOES-18 which shows the launch in the water vapor bands

Finally, @SpaceX has also posted a video showing the deployment of the satellite, with an impressive shot showing how far away it is from the Earth.

Thank you to 'Tuned Signal' (TS) for sharing his video with impressive production quality, detailing his story on how and why he became hooked on software-defined radio. TS notes how it all started with an Outernet receiver that he purchased, which came with an RTL-SDR dongle. From there he ended up purchasing higher end SDRs and learning more about the different types of signals he could receive.

If you're interested, check out some of his other videos on his YouTube channel which cover topics like how to receive train radios, how to listen to CB radio and more.

Paolo Romani (IZ1MLL) has recently released the 2024 version of his SDR# Big Book. The book is available for download on the Airspy downloads page, just scroll down to the title "SDR# Big Book" and choose your language. (At the time of this post only English and Italian are available in the 2024 edition, but multiple languages are available for the older guides).

Paolo writes that the book has been updated for the latest SDR# v1920 version, and now the editions will be labelled by date, instead of version number. He also writes that page 25 of the big book now includes information about the differences between RTL-SDR Blog V3 and V4 dongles. 

Over on YouTube Matt from the Tech Minds YouTube channel has tested out NooElec's new 'FlyCatcher', which is an RTl-SDR ADS-B hat for the Raspberry Pi. The FlyCatcher has two RTL-SDRs built into it, each with it's own LNA and SAW filter. One SAW filter is tuned for 978 MHz UAT, and the other for 1090 MHz ADS-B.

The device also has buttons that allow you to bypass the LNA stage, and just use filtering, in case you have an external LNA. They appear to be using the Qorvo TQL9063 LNA chip, which has a built-in bypass.

In the video Matt tests out the FlyCatcher, but only on 1090 MHz as 978 MHz UAT is not used in his country. He shows how to set up the software on the Raspberry Pi and then shows some results.

Over on his YouTube channel, Aaron, creator of DragonOS and WarDragon has uploaded a video showing how it is possible to decode Meshtastic with an RTL-SDR and GNU Radio project called Meshtastic_SDR. 

If you weren't aware of it, Meshtastic is software that enables off-grid mesh network based communications and can run on cheap LoRa hardware. The mesh based nature of the system means that communications can be received over long distances, without any infrastructure, as long as there are sufficient Meshtastic nodes in an area that are able to route the message to the destination node. One example application of Meshtastic is to use it as a mesh-based text messaging system. This might be useful for teams of hikers, pilots, or skiiers who operate in remote areas without cell phone coverage.

In the video, Aaron shows how to install the Meshtastic GNU Radio software on DragonOS (Linux), and how to run the GNU Radio flowgraph and Python decoder script. Later in the video Aaron shows some test text messages being received by the software.

The Meshtastic_SDR project can also be used to transmit Meshtastic messages with an appropriate TX-capable SDR.

Back in 2019 we posted about the release of Artemis 3, an open-source multi-platform program that makes searching through the Signal Identification Wiki offline possible and easy to do.

Recently Artemis 4 has been released which is an entire rewrite of the code, resulting in some substantial improvements, and paving the way for future features like machine learning based identification. Author Marco Dalla Tiezza writes:

• Artemis was initially designed to provide an offline solution for consulting the library of signals provided by the community on sigidwiki, but the database was formerly a simple .csv with all its limitations. Now the database is a proper relational sqlite which is much easier handled and offers many other possibilities like: additional fields (for example, each frequency of a signal can contain a description and this is true for every single parameter), faster db operations (for example, filtering signals is done by a simple query), increased extensibility due to the fact that new fields/parameters can be introduced in the future or by the user itself.

• The only searchable database with Artemis 3 was the Sigid wiki database.Now, with Artemis 4, users can create their own custom databases, enter an arbitrary number of signals and parameters, attach documents or any useful information, and export it by sharing it with their friends.

• The documentation has been completely revised to be as clear as possible and to be able to take the user from installation to advanced use of the program by giving instructions on how they can contribute to the project. DOCUMENTATION
  

• As usual, the program provides a real-time interface to be able to track space weather in near real-time, but now this module is more focused on RF propagation such as meteor scatter, EME, sporadic E, aurora spots, DRAP, aurora forecasts and many more (we are actively adding useful descriptors).

• Artemis 4 now relies on the PySide 6 graphics framework, which not only allows for a modern and newer, user-customizable GUI but also allows for less use of third-party libraries to run the program.
  

• Given the flexibility and especially the modularity of the new software, it is very likely that signal analysis functions will be introduced in the future (such as automatic recognition of signals via machine learning/neural network or simpler ones like FFT for obtaining ACF from an audio file, etc.)

• The homepage of the project (https://www.aresvalley.com) as been updated as well and there you can see some screenshots or directly download the software to give it a try.

If you weren't aware, the Signal Identification Wiki (sigidwiki) is our sister site, which we started a few years ago to collect and catalog various types of signals that an SDR user might see and hear on the airwaves. The idea is that a user could search the database to learn about and identify unknown signals. Over time it has grown significantly, now over 500 known signals with both waterfall images and sound samples available in the database. We have since handed over the operation of the Wiki to the community, with Carl Colena taking on the lead.

Welcome back to Sarah from the SignalsEverywhere YouTube channel who has recently returned to producing videos from a hiatus. In her latest video, Sarah shows off her new OP25 Mobile Control Head Android App which allows you to implement a full P25 digital radio scanner at a fraction of the cost of a commercial digital scanner. In the past, Sarah had released a similar application written for the Raspberry Pi but has decided to shift her focus to writing an equivalent Android app that is less clunky and can be deployed for a lower cost. 

The app controls and displays information from the OP25 software that runs on a Raspberry Pi with RTL-SDR connected. It works by using a server application on the Raspberry Pi that manipulates the OP25 instance and its configuration files.

Sarah writes:

The application is a wrapper for OP25 that uses a raspberry pi and an android device to provide users with a mobile control head for their OP25 P25 scanner setup. Currently it's just a basic application but I'll be adding features like automatic site switching, etc.

OP25MCH: https://github.com/SarahRoseLives/OP25MCH

There is also a separate application I call the OP25Display which is just a display for a users existing OP25 instance.

OP25Display: https://github.com/SarahRoseLives/op25display

Over on Hackaday, we've seen a post about Jay Doscher's clever 3D printed enclosure that can hold two RTL-SDR Blog V4 units and a USB hub. The enclosure is designed to make it easy to take the two units mobile, and the USB hub inside means that only one USB connection is required to run the two units.

Jay has also thought about cooling, allowing for space between the two dongles, and adding vent holes. He has also ensured that the SMA ports on the dongles are protected while allowing space to hand-tighten the connectors.

Jay writes that he has tested his enclosure with RTL-SDR Blog V4 units, but given that the dimensions of the V3 (and V2) are the same, it will work for those units too.

Thank you to Viol for writing in and letting us know that his uSDR software has recently been updated to V1.7.0. The uSDR software (not to be confused with the unrelated uSDR hardware) is a lightweight general-purpose multimode program for Windows that supports the RTL-SDR, Airspy, BladeRF, HackRF, LimeSDR, and other SDR radios.

Viol highlights the latest features added in the 1.7.0 update below:

• Fobos SDR frontend native support, the very new SDR from RigExpert
• bladeRF API v2.5.0 support, oversampling mode up to 122.88 MHz sample rate (do not forget to update FX3 firmware)
• advanced IQ playback mode, precise timing and streaming
• improved DSP routines and memory management, minimized CPU load
• excellent ruler tool for spectrum frequency and amplitude measurements

Over on his YouTube channel, Rob VK8FOES has started a new video series about Iridium Satellite Decoding. Iridium is a constellation of low-earth orbiting satellites that provide voice and data services. Iridium was first decoded with low cost hardware by security researchers back in 2016 as mentioned in this previous post. Being unencrypted it is possible to intercept private text and voice communications.

Rob's video is part of a series, and so far only part one has been uploaded. The first video outlines the hardware and software requirements for Iridium decoding and demonstrates the gr-iridium software. An Airspy and RTL-SDR Blog Patch Antenna are used for the hardware, and the software runs on DragonOS.

Rob writes that in part two he will demonstrate the use of iridium-toolkit, which can be used to extract data and recordings from the Iridium data provided from gr-iridium.

Be sure to subscribe to his YouTube channel so that you are notified when part two is released.

The company "DeepSea Developments" have recently released news about their upcoming crowdfunding campaign for their 'DeepRad' modular RTL-SDR system. The goal of DeepRad appears to be a modular RTL-SDR that can easily be used as a module on a 'motherboard' PCB of your own design.

DeepRad is currently in the 'Coming Soon' stage on CrowdSupply, and will probably be released for crowdfunding in the next few months.

DeepRad is a modular version of the RTL-SDR, a product beloved by radio enthusiasts. However, DeepRad offers distinct advantages. Its modularity makes integration far simpler, side-stepping the complexities of designing an RTL-SDR from scratch (such as RF considerations and chip stocking issues). DeepRad is a versatile option for integrating many different radio functions into whatever projects you’re working on today.

We want the community to create their own "motherboards" with 1, 3, or as many as 20 DeepRad modules to bring new applications to life. There are three versions of DeepRad we’ll be focusing on for this campaign:

• DeepRad Module: The bare DeepRad module (no motherboard). The user has to develop a board to use it.
• DeepRad Single: A single DeepRad module with a motherboard. It has USB Type-C and an antenna connection. It can be used as your regular RTL-SDR with USB.
• DeepRad Quad: A motherboard with 4 DeepRad modules integrated via a USB hub with a USB Type-A connector.

In the past, we've shown how it's possible to use RTL-SDRs or other SDR devices together with the Airprobe software to analyze data from 2G GSM mobile phones and towers. (Note that it's not possible to listen in on conversations or read SMS data unless you have the encryption code for the recipient phone. This is only capable of showing cell tower basestation telemetry for example).

While not directly related to SDR, readers might be interested to know that a new piece of software called QCSuper has been released which enables similar analysis capabilities for 2G/3G/4G/5G signals through the use of Qualcomm-based phones and modem hardware. To use it you will need a rooted Android phone. The software accesses a diagnostics mode available in Qualcomm devices and makes the data available for view on Wireshark.

[Also seen on Hackaday]

Over on YouTube sn0ren has uploaded a well produced video to help beginners to the radio hobby understand antennas. The video explains how antennas work in theory, and how to choose the best antenna for your SDR and application through calculations and use of a Nano VNA.

There is an essential gadget that you will want to get, to get the best antenna performance. But first we need to cover a bit of antenna theory, before we can answer the question of what antenna that is the best one for your HackRF Portapack, or Flipper Zero SubGHZ module, or Meshtastic, Quansheng UV-K5, RTLSDR or other radio devices. This video is covering the bare minimum basics of antenna theory for beginners into the radio hobby.

A few days ago SDRSharp version 1920 was released. SDRSharp (SDR#) is a popular Windows program that is affiliated with Airspy SDR dongles, but is compatible with RTL-SDR and various other SDRs as well. The latest version gets rid of the relatively resource heavy Telerik UI library and replaces it with a much lighter weight library.

The author of SDR#, @lambdaprog, notes that v.1920 reduces memory usage by 85% and CPU utilization by 50%. The new version also improves scalability for high sample rates and number of spectrum slices and improves plugin compatibility. Several AOR brand SDRs are also now supported in v.1920.

On the note regarding improved plugin compatibility, we've noticed that in the v.1920 update the IF Average plugin has begun working again. The IF Average plugin is used for Hydrogen line radio astronomy experiments. In the past we had to use older versions of SDR# to make it work. We have updated our Hydrogen line tutorial to reflect this.

Thank you to RTL-SDR.COM reader Lee. who found a recently released program called "gypsum" which enables an RTL-SDR or HackRF to be used as a GPS Receiver when combined with a GPS antenna. Phillip Tennen, the author of Gypsum notes that Gypsum can obtain a fix within 60 seconds from a cold start and that it has no dependencies apart from numpy. We want to note that it appears that Gpysum has no live decoding ability yet, as it works from pre-recorded GNU Radio IQ files.

In the past, we've shown in a tutorial how GPS can be received and decoded with GNSS-SDRLIB and RTKLIB on Windows. The new Gypsum software should work on Linux and MacOS too.

What's more, Phillip has written an incredible 4-part writeup on how Gypsum was implemented from scratch. In the write-up, Phillip introduces GPS and explains how it can even work with such weak signals that appear below the thermal noise floor. He then goes on to explain how the detected signal is decoded and turned into positional information, and how challenging it was to propagate the accurate timing information that calculating a solution requires. The write-up is presented with clear visualizations to help readers intuitively gain an understanding of the advanced concepts involved.