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.
Thank you to Adrian (YO8RZZ) for writing in and sharing with us his article explaining how to use an SDR to set up a digital voice hotspot for digital voice modes supported by MMDVM such as D-Star, DMR, System Fusion, P25 and NXDN. Adrian notes that this is possible with any full duplex SDR such as the LimeSDR or PlutoSDR, or with a combination of simplex devices, such as a HackRF for transmitting combined with an RTL-SDR for receiving.
MMDVM is firmware that normally runs on an ARM microcontroller board such as the Arduino Due, and is designed to be interfaced with hardware radios via the microcontrollers built in ADC and DAC hardware.
In order to use an SDR instead of physical hardware radios, Adrian's article describes how a fork of MMDVM called MMDVM-SDR is used in his system as this allows the code to run on a normal Linux computer with an SDR. GNU Radio running on Adrian's own QRadioLink software is then used to create software ADC/DAC interfaces for the SDR and MMDVM-SDR to interface with, as well as providing a user interface.
In his latest episode of his SDR Guide series Rob from Frugal Radio provides a walkthrough on using DSDPlus Fastlane to decode trunked P25 with just one RTL-SDR V3 dongle. In the video he explains each of the various DSDPlus windows, and demonstrates decoding of a Simulcast system in his area.
DSDPlus is a program capable of decoding various digital audio protocols such as DMR and P25. The "Fastlane" version is a $25 paid upgrade which allows you to download the latest version that contains more features.
In this weeks episode of Frugal Radio's SDR Guide videos Rob shows how a FM bandstop filter can help in certain situations. A FM bandstop is designed to reduce the power level of FM broadcast stations that are received by your antenna. FM broadcast stations are often extremely strong, and this can cause an SDR to overload, resulting in poor reception on other frequencies.
In the video he demonstrates how he is unable to receive air traffic control signals due to FM broadcast overload. After inserting an FM bandstop filter the air traffic signals become receivable. We note that we sell a low cost FM bandstop filter in our store.
In a second video Rob demonstrates the use of the recently released Simple DMR plugin which we posted about earlier.
At the beginning of 2020 Annunaki (@StupotSinders) released his third party user interface for DSDPlus. DSDPlus is a digital speech decoder capable of decoding protocols such as P25 P1, DMR, NXDN and more with an SDR such as the RTL-SDR. As it is a command line tool, it can be a little daunting for some users, which is where the GUI comes in handy.
Recently Annunaki has released an SDR# plugin version of DSDPlusUI. This makes it so you can visualize the digital voice signals at the same time as controlling and decoding with DSDPlus. The plugin is available on the DSDPlusUI website at dsdplusui.com. To use it you will need to be using SDR# 1777 or later.
In this episode of Frugal Radio's ongoing SDR guide videos Rob demonstrates how you can use an RTL-SDR with DSDPlus to monitor DMR and NXDN digital voice radio communications. Rob writes:
With a simple Software Defined Radio (SDR) and some free or frugal software, you can monitor digital radio systems like DMR and NXDN in your area.
his video is a demonstration of how I set up DSDPlus to monitor DMR and NXDN networks, and shows how to modify the various files that help the software trunk track the system with your SDR.
More details with links to the software (DSDPlus) and hardware (1 x RTL-SDR v3) I used in this video can be found at https://frugalradio.com/monitor-dmr
f you are unsure about how trunking systems work, I suggest watching the overview at the beginning of Episode 6 - https://youtu.be/zuUTXHbUvpw
Simple DMR decoder. No external dependencies, no settings, uses SDR # audio path. Designed for listening to unencrypted DMR channels. The voice from both slots is mixed into one channel.
To install the plugin simply copy the dll's from the zip file into the SDR# folder, then copy the line from the magline.txt text file into the plugins.xml file which can be opened with any text editor.
Over on YouTube TechMinds has posted his latest video which shows an overview of the features available in OpenWebRX, and also how to set it up on a Raspberry Pi. OpenWebRX is software which allows you to access your SDR remotely via the internet or local network through a web browser. All major SDRs are supported including RTL-SDRs. The software includes a waterfall display, all the standard demodulators, as well as several digital decoders for DMR, YSF, NXDN, D-Star, POCSAG, APRS, FT8, FT4, WSPR, JT65 and JT9.
In the video TechMinds first demonstrates OpenWebRX in action, showing reception of HF SSB amateur radio signals, decoding FT8 and plotting received grids on a map, decoding and plotting APRS on a map and decoding YSF/DSTAR/DMR digital voice. After this demonstration he goes on to show how to set up the OpenWebRX server on a Raspberry Pi via the installation image.