The New York Times have recently run an incredible video story about how Russian radio communications are being intercepted and recorded by ham radio operators and open source radio monitoring hobbyists in Ukraine. Some of the communications reveal the extent of the logistical issues experienced by the invading forces, and perhaps have even recorded evidence for war crimes.
It appears that much of the invading Russian forces use simple unencrypted analogue voice over HF channels that can be intercepted and recorded by anyone with an HF software defined radio, or anyone willing to monitor nearby web-based SDRs like KiwiSDRs and WebSDRs. In the video screenshots of recordings played back in SDR# and various WebSDRs are displayed.
The story focuses mostly on the audio recordings that highlight communications between Russian forces discussing attack plans, including plans to bombard residential areas with artillery. These recordings are cross-referenced with reports and videos of actual tank sightings and destruction in the areas discussed on the radio.
A later recording highlights communications from a distressed Russian vehicle under attack, requests for air support being unfulfilled, and urgent requests for supplies like fuel, food and water.
Russia Struggled to Capture a Ukrainian Town. Intercepted Radio Messages Show Why.
Some of the monitoring projects involved are highlighted in the story and they include, Project Owl, Ukrainian Radio Watchers, ShadowBreak and NSRIC (Number Stations Research and Information Center). We are also aware of at least one other organization attempting to record communications within Ukraine as well that may be making use of RTL-SDRs, HackRFs and other SDRs.
With the rising cost of computing hardware like Raspberry Pi's, Jaime Badillo decided to instead make use of one of a cheap old router, and set it up as an RTL-SDR server. To do this, Jaime took his old router and installed on it the free open source firmware OpenWRT, which is essentially a Linux operating system. Once this was completed, he was able to SSH into the router and install the RTL-SDR drivers and rtl_tcp software just as he would with a Raspberry Pi 4.
SDR++ is a general purpose receiver program compatible with almost any software defined radio including the RTL-SDR. Recent developments have seen the author release a beta of "SDR++ server" which is a program that allows users to access SDRs remotely, by connecting to them over a network connection. This is similar to existing server applications like rtl_tcp and Spyserver, however like SDR++ itself, SDR++ Server is compatible with almost any SDR and that is a major drawcard.
Today I'm happy to release the beta version of SDR++ Server! It works with all devices SDR++ supports. Since it's beta it's still missing compression and VFO+FFT mode.
As a demo, here is a LimeSDR being streamed over WiFi at 16MS/s
Get it here: https://t.co/DqvgHMZmm9#SDR#SDRPPpic.twitter.com/116JftzEOy
The server is still in development and the author notes that he is still working on adding new features like lossless compression techniques in order to reduce network bandwidth requirements. However, it has already seen to be running well in tests with a remote server positioned half way around the world, even without compression enabled.
Started working on adding lossless compression to SDR++ server. How well it works depends on what signals you're looking at and what SDR you're using. What I'm seeing with general purpose compression tables is 1.1 to 2.5 times compression (usually 1.5+). Custom tables should help pic.twitter.com/a1WRvxmdDs
Over on YouTube TechMinds has recently released a video where he overview SDR++, dubbed as the "bloat free SDR software". We've been following the development of SDR++ for a while, and recently posted about the release of version V1.0.0. SDR++ is an open source, cross platform, C++ based GUI general receiver program for various SDRs including the RTL-SDR. In another recent post we also saw a video review from Sarah at SignalsEverywhere.
The the video TechMinds gives an overview of the SDR++ features and GUI, and also shows DSD+ and WSJT-X running together with it. He notes that SDR++ lives up to it's expectations and lives up to it's bloat free tagline.
Libre Space Foundation ( Greece) and the Institute of Reconfigurable & Embedded Digital Systems(REDS) of the Haute Ecole d’Ingénierie et de Gestion du Canton de Vaud – HEIG-VD (Switzerland) have been implementing a number of smaller projects as part of an Software Defined Radio MakerSpace of the European Space Agency.
This activity is part of the ARTES programme of ESA that supports innovation in satellite communications.
The findings were presented in three 2-hour slots in the afternoon at 15:00 CEST (for which you are requested to register separately) on Mon 6, Tue 7 and Wed 8 September 2021.
Monday 6 Sep was focused on the evaluation of various SDR boards and FPGA tools chains. High-rate direct sampling by SDR’s and SDR on Android will also be presented.
Tuesday 7 Sep was dedicated to building blocks that have been implemented as open source developments for Gnuradio, such as gr-leo, gr-ccsds, gr-soapy etc.
Wednesday 8 Sep was mainly about the combination of SDR and AI/ML to do signal detection and classification. In addition, an SDR testbed and spectrum monitoring will be presented.
The talks cover various SDR topics related to satellite observing. Some talks we were interested in are highlighted below, but the full list can be found on the SDRMakerspace website, or the SDRMakerspace playlist on the Libre Space Foundation YouTube channel.
HamSCI is an organization dedicated citizen radio science and specifically the "publicity and promotion of projects that advance scientific research and understanding through amateur radio activities". Back in March they held their HamSCI 2021 workshop online, and the videos from presentations and posters are now all available on the Ham Radio 2.0 YouTube channel.
Most of he presentation videos were released back in June, but the poster talks were just released in the past few days. Many of the projects mentioned in the talks involve the use of software defined radios.
Broadcast FM channels can often contain additional subcarriers hidden within the bandwidth. A common subcarrier is Radio Data System (RDS), and this is what provides song and radio station text information to your radio.
Another less commonly seen subcarrier is the Subsidiary communications authority (SCA), which is a separate audio channel hidden within the broadcast FM signal. SCA is typically used for niche radio programs, elevator music, music for doctors offices, and niche services such as reading for the visually impaired. In the past you needed a special hardware SCA radio to receive these channels, however receiving these channels with an SDR is relatively simple. Not all broadcast FM stations will have an SCA service, but the video shown below explains how to find one.
Over on YouTube channel Double A has uploaded a video showing how to decode these SCA subcarriers using an RTL-SDR, two SDR# instances and the MPX Output plugin. The idea to to use a virtual audio cable to pipe the FM Multiplex (MPX) audio output from one instance of SDR# to another. In the second SDR# instance you can then directly tune into the SCA channel. In his video he also explores the FM MPX spectrum, showing the different components, and also how to install and use RDS Spy for decoding RDS.
Tuning an FM Audio Subcarrier (SCA) & Decoding RDS Data with RTL-SDR USB
Paolo Romani (IZ1MLL) has recently released version 3.0 of his SDRSharp PDF Guide which we posted about last in March of this year. As before the document is a detailed guide about how to use SDRSharp, which is the software provided by Airspy. While intended for Airspy devices, SDRSharp also supports a number of third party SDRs, including the RTL-SDR, and it is the software we recommend starting with when using an RTL-SDR.
The guide is now 61 pages long, and covers all the settings, UI customization, included and third party plugins, and use of some external decoders.