Category: Digital Signals

TechMinds: Testing the ISM Packet Decoder Plugin for SDR Sharp

Over on the TechMinds YouTube channel Matt has uploaded a video demonstrating the use of the ISM Packet Decoder plugin for SDR# which was released a few months ago. The plugin authors website also contains more information about the installation and features of plugin.

The plugin makes use of the well known rtl_433 software behind the scenes, which is a command line based RTL-SDR compatible decoder for various wireless ISM band devices such as weather stations, car keys, tire pressure sensors, doorbells and various other remote controlled devices. The plugin GUI makes using and displaying data from rtl_433 much more convenient.

ISM Packet Decoder Plugin For SDR Sharp - RTL 433

Probing a Cable Internet + TV Line with RTL-SDR USB

Thank you to Adam from Double A Labs for submitting his latest YouTube video where he uses his RTL-SDR to probe the coaxial cable that provides his broadband internet and cable TV. In the video Adam explains how hybrid fiber-coaxial internet and TV broadband networks (such as Comcast/Xfinity) work, and how the Specktrum software can be used with an RTL-SDR to explore the spectrum on these cables. Adam writes:

What I found was pretty interesting, including a few unmodulated analog TV carriers on the line producing a black screen on my TV. I also explain how coaxial broadband networks work (bi-directional amplifiers, upstream/downstream splits, etc.) and how internet service providers are upgrading them.

How Broadband Cable Networks (Xfinity etc.) Work and Probing One with a Spectrum Analyzer (RTL-SDR)

Feeding ACARS Data to

Thank you to a contributor for submitting an article about, which is an ACARS/VDL2/HFDL/Satellite ACARS aggregation site. The article below it attributed to Kevin Elliott and was edited by Frank Vance. They would also like to attribute the large group or volunteers at

One of the most popular hobbyist uses of SDR is receiving and decoding vehicle information data such as ADS-B for aircraft or AIS for marine traffic.  Some hobbyists have been banding together to exchange their mutual data streams to provide coverage over wide geographic areas.

One of the largest and most successful such projects in the aviation realm is ADS-B Exchange (, where over 8,000 volunteer feeders provide ADS-B data to a global aviation map in real time.  

But modern air carriers have much more data to and from their aircraft than just the position information from ADS-B.  In the 1970s, ACARS was created to carry that traffic.  Today, ACARS is seen on its own frequencies on VHF, embedded in AVLC on the VDL2 VHF frequencies, on HF (shortwave) frequencies using the HFDL network of stations worldwide, and on satellite on both the Inmarsat (ACARS over AERO, or AoA) and the Iridium (called ACARS over Iridium, or AoI) systems. ( is a project that has been under development for a while to aggregate ACARS data in the same way ADS-B Exchange is aggregating ADS-B data.  Under the capable leadership of Kevin Elliott (, software development has progressed to the point that new feeders are actively being sought to improve the global coverage and provide a broader base of data to improve the decoding.

With a wide variety of data sources, this is a collaboration project that is open to all levels of SDR hobbyists.  A simple RTL-SDR.COM unit attached to a Raspberry Pi with a smaller antenna works well with the VHF coverage.  Depending on one's interest level, an HFDL feeder may require multiple SDRs with much broader frequency range, capable of reception in the sub-30 MHz bands.  The L-band based Iridium AoI uses a small antenna as well, but requires a wide bandwidth SDR.  Finally, reception of the C-band Inmarsat (AoA) traffic may involve a moving dish antenna of at least 6 foot diameter to obtain usable signals.

What kind of data is seen in ACARS?   One can observe weather conditions aloft, messages to/from the carrier operations staff, information about the origin and destination of the flight, and technical data on the aircraft operation (not all of which can be decoded at this time.)  Additionally, the HFDL and satellite feeds offer location information out of sight of the traditional ADS-B coverage, such as over the oceans and polar regions.
The About page at ( has plenty of good information to help anyone get started with feeding, including links to popular software packages useful for running different types of feeders.  Support is available on the #airframes-io channel ( on the ADSBExhange Discord server (
Additional information about setting up a receiver/feeder for HFDL, Inmarsat L-band, Inmarsat C-band, and Iridium L-band is available on The Bald Geek's GitHub page: joining with the dozens of volunteers already feeding and contributing software updates to the project. Map ACARS Messages

Frugal Radio: Experimenting with Rdio-Scanner and Trunk Recorder on P25 LSM

In his latest video Rob from the Frugal Radio YouTube channel has uploaded a video where he experiments with a SDR web interface and smartphone App called "Rdio-scanner". Rdio-scanner is an interface that tries to reproduce the user experience of using a real hardware scanner with an SDR and RF voice decoding/recording software like Trunk Recorder being used in the background. Rob writes:

rdio-scanner creates a customizable web interface from which to control your software defined radio. Using it, you can turn a computer, phone or tablet into something that closely resembles a hardware scanner!

Trunk Recorder is the software that decodes the unencrypted P25 signals and records them to disk. Here is it demonstrated working on a large Simulcast (LSM) site.

rdio-scanner reads the audio files. Through the rdio-scanner interface, you are basically choosing which audio files to play.

Rob runs the rdio-scanner software on his Panasonic Toughbook, noting that the interface looks really great in Tablet mode and works well with the touchscreen. He also notes that his toughbook has a SIM card socket, so a data SIM would enable him to access his P25 monitoring system at home from anywhere. 

SDR experiments with Rdio-scanner, Trunk Recorder, Airspy Mini & Panasonic Toughbook on P25 LSM

SignalsEverywhere: Playing Classic Games over Amateur Radio with NPR-70 TCP/IP Modems

Over on her YouTube channel SignalsEverywhere, Sarah has uploaded a new video that shows us how TCP/IP connections can be made over the amateur radio spectrum using low cost NPR-70 TCP/IP modems that operate in the 70cm amateur band at around 433 MHz.

With a TCP/IP connection available it is then possible to play games over the amateur radio bands and Sarah demonstrates this in action with some classic games like Unreal Tournament 2004, noting that the ping was about 225ms. She notes that she used a lower symbol rate to keep within the legal limits within the USA, however in other regions a higher symbol rate may be possible, resulting in better ping. She goes on to try a strategy game called OpenRA which is a bit more suited to running on low speed high latency networks, noting that the radio TCP/IP connection worked very well.

In the video Sarah also shows what the modem signal looks like on the spectrum and waterfall using SDR++.

Playing Classic Games over Amateur Radio | NPR-70 Modem TCP/IP Unreal Tournament and OpenRA

Using an RTL-SDR to Decode Broadcast FM RDS Data on Android

Over on YouTube Double A Labs has posted a new video demonstrating how to use an RTL-SDR and Android device to receive broadcast FM stations, and to decode any associated RDS data. 

In the video Double A uses the SDR Touch Android app and the Advanced RDS function to show the RDS information. He goes on to explain the various pieces of information RDS data provides including clock time, active RDS groups and alternative frequencies.

Tune broadcast FM radio and decode Radio Data System (RDS) information using your Android phone and an RTL-SDR USB (see parts list below). RDS can include station identification, song name, the current time for a receiver to sync its clock, alternative frequencies the same program is on, and more!

Tuning FM Radio & Decoding RDS Data on ANDROID using RTL-SDR USB

Frugal Radio: Travelling with SDR & Scanner Gear

Over on his YouTube channel Frugal Radio, Rob has uploaded a new video whilst on holiday travelling through the USA. In the video he shows what sort of scanner radios, antennas and SDR gear he carries with him on his travels. His gear includes a Uniden SDS-100 scanner, a BCD325 scanner, a Radio-Tone RT4 internet network radio and of course an RTL-SDR Blog V3 and laptop.

He goes on to demonstrate the hardware in action from his Hotel room, decoding local digital audio.

A peek in Frugal's Travel Bag : SDR & Scanner gear on the road

Lon.TV Demonstrates Decoding Various Digital Signals with RTL-SDR

Tech YouTuber Lon.TV has recently uploaded a video demonstrating how to identify and decode various digital transmissions with an RTL-SDR dongle. In the video he explains how to use VB Cable to pipe audio from SDR# into various decoders, and then goes on to show DMR, APRS, POCSAG, L-Band AERO, FT8, and JS8/JS8CALL all being decoded via an RTL-SDR Blog V3 dongle.

Software Defined Radio Part 2 - Decoding Digital Transmissions with an RTL-SDR USB Radio