Tagged: NXDN

A SDR Digital Voice Hotspot with GNU Radio, MMDVM and QRadioLink

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.

QRadioLink used as the UI for MMDVM-SDR and GNU Radio

Frugal Radio: SDR Guide Ep 7 – Trunk DMR & NXDN digital with DSDPlus and One RTL-SDR

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

2020 SDR Guide Ep 7 : Trunk DMR & NXDN digital with DSDPlus and 1 RTL-SDR

TechMinds: OpenWebRX Feature Overview And Raspberry Pi Setup

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.

OpenWebRX Feature Overview And Raspberry Pi Setup

Listening to and Tracking NXDN/IDAS Trunking Systems with two RTL-SDRs

Over on YouTube user radiosification has uploaded a video tutorial that shows how to decode, follow and listen to NXDN/IDAS trunking radio signals. NXDN/IDAS is a narrowband digital voice protocol commonly used with handheld radio terminals.

In the tutorial radiosification explains how to set up DSDPlus and its frequencies text file to automatically listen to and track conversations using the control channel. SDR# is initially used to find the NXDN control and voice channels, which are then entered into the text file. Using this method only DSDPlus and its corresponding receiver FMP is used. Trunking software like Unitrunker is not needed.

Radiosification also notes that the method he presents can also be used for other digital trunking systems such as P25 as well.

How to track NXDN trunking with RTL SDR & DSDPlus

Listening to NXDN with SDRSharp, the AuxVFO Plugin and DSD+

Over on YouTube user John Miller has uploaded a video showing how he receives NXDN digital audio using a combination of SDR#, the AuxVFO plugin and DSD+. He writes:

I have it set with 5 auxiliary VFO’s one for each channel of the Christian Co NXDN system from the Kelly Towers. I use VAC to route the audio from each VFO to DSD+ each VFO has it own DSD+ running. I then have all the DSD+ go into one output VAC and use that to run a feed on Broadcastify, The secret to running multiple DSD+ is to have separate install of it, so I have 5 DSD+ folders.

Decoding NXDN using DSD+ and an RTL-SDR

Over on YouTube user John Miller has uploaded a video showing an example of DSD+ decoding an NXDN96 voice signal. NXDN is a digital voice protocol by developed by Kenwood that is often used by public safety organizations.

John uses SDR# to receive the NXDN signal and then pipes the audio to DSD+ using Virtual Audio Cable for decoding.

DSD+ Decoding NXDN