Category: Digital Signals

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

Frugal Radio: SDR Guide Ep 6 – Trunk Tracking Public Safety Systems with UniTrunker and SDRTrunk

In this episode of Frugal Radio's ongoing SDR Guide videos Rob demonstrates how he uses Unitrunker and SDR Trunk with SDRs like an RTL-SDR to monitor Public Safety networks in his area. Rob writes:

This is a video demonstrating how I use UniTrunker and SDRTrunk with Software Defined Radios to monitor multiple Public Safety networks in my area.

There is some information on how trunked systems work, and you can hear how my SDRs produce better P25 audio on a Simulcast (LSM) system than some scanners.

I use a couple of RTL-SDR v3s and an Airspy R2 in this episode.

2020 SDR Guide Ep 6 : Trunk tracking Public Safety systems with UniTrunker and SDRTrunk

Simple dPMR Decoder Plugin for SDR# Released

Over on rtl-sdr.ru programmer Vasili has released his latest SDR# plugin which is a dPMR decoder (note that this site is in Russian). dPMR is short for "Digital Private Mobile Radio" and is an open non-proprietary digital voice protocol. Vasili writes:

Simple dPMR decoder. No external dependencies, no settings, uses SDR # audio path. Designed for listening to unencrypted dPMR channels.

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.

We note that there is also an open source version of DSD which includes a dPMR decoder which we posted about here.

Simple dPMR Decoder Plugin for SDR#

Simple APCO P25 Phase 1 Decoder Plugin Released for SDR#

Vasili, author of several SDR# plugins has recently released a new APCO P25 plugin for SDR#. The plugin is easy to use, simply tune to a P25 voice signal, and it will automatically decode it into voice audio assuming that the signal is not encrypted. If the P25 signal is encrypted, you will hear garbled unintelligible voice. The plugin does not support trunking or any advanced talk group filtering features that you might find with DSD+, Unitrunker, SDR Trunk etc.

To install the plugin, simply download the zip file from rtl-sdr.ru and extra the .dll's into the SDR# folder. Then copy the text in magicline.txt file into the plugins.xml file inside the SDR# folder. The plugin should work with any SDR supported by SDR#, including the RTL-SDR.

The simple APCO P25 decoder for SDR#

Decoder for Geostationary Elektro-L Weather Satellites Released

Elektro-L is a range of Russian geostationary weather satellites. Elektro-L1 and L2 were launched in 2011 and 2015 respectively, and Elektro-L3 was launched more recently in December 2019. Currently only Elektro-L2 and L3 are in operation. Like it's NOAA GOES, Himawari and GK-2A cousins, Elektro-L satellites beam back full disk images of the entire earth.  Elektro-L2 is positioned to cover South America, Africa and Europe, whilst Elektro-L3 covers the East of Africa, Eastern Europe, Russia, Middle East, Asia and the West of Australia.

Elektro L2 and L3 Coverage from https://www.wmo-sat.info/

Recently @aang254 has been Tweeting that he has managed to get an Elektro-L decoder working. The decoder is open source and available on GitHub and Windows builds are already available. He notes that he's still working on the demodulator, but that should be released tomorrow. This decoder is great news as now Europeans now have an opportunity to receive full disk images. There is no full guide yet on how to use the decoder, but we expect that one will be released soon.

We note that according to wmo-sat.info the Elektro-L satellites transmit at ~1693 MHz, and have a 2 MHz wide HRIT and 200 kHz wide LRIT mode. So the signals should be able to be received with an RTL-SDR and appropriate LNA. EDIT: Unfortunately it seems that wmo-sat.info may have incorrect information, and that Elektro-L requires X-Band hardware to receive these images. While not totally impossible, an X-Band satellite SDR setup is a bit more difficult to put together compared to the L-band SDR setup used by GOES and GK-2A.

DragonOS: Installing Crocodile Hunter For Detecting Fake 4G Cell Sites

A few days ago we posted about two SDR related DEFCON talks which were recently released. One of the talks was about detecting fake 4G base stations with a bladeRF SDR and a tool they created called "Crocodile Hunter". It is currently compatible with the bladeRF x40 and USRP B200. The talk summary is posted below as it nicely summarizes what fake 4G base stations are and what Crocodile Hunter can do.

4G based IMSI catchers such as the Hailstorm are becoming more popular with governments and law enforcement around the world, as well as spies, and even criminals. Until now IMSI catcher detection has focused on 2G IMSI catchers such as the Stingray which are quickly falling out of favor.

In this talk we will tell you how 4G IMSI Catchers might work to the best of our knowledge, and what they can and can't do. We demonstrate a brand new software project to detect fake 4G base stations, with open source software and relatively cheap hardware. And finally we will present a comprehensive plan to dramatically limit the capabilities of IMSI catchers (with the long term goal of making them useless once and for all).

The Crocodile Hunter software is apparently a little difficult to install and get running, so Aaron who runs DragonOS YouTube tutorial channel has uploaded a video documenting how to install and configure the software. The tutorial assumes that you are the running the latest DragonOS image which already includes a lot of the prerequisite software, and in his example he uses a USRP B205mini-i SDR.

DragonOS DEF CON 28 Crocodile Hunter Setup (DragonOS LTS PublicR4, srsLTE, USRP B205mini-i)

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

MySondy: Radiosonde Tracking Firmware for a TTGO ESP32 LORA Board

A radiosonde is a small sensor and radio package normally attached to a weather balloon. Meteorological agencies around the world typically launch two balloons a day from several locations to gather data for weather prediction. We have featured radiosondes several times on this blog as it is easy to use an RTL-SDR and computer to receive and decode their signals, which can used to hunt down the fallen sonde, or to receive the weather telemetry data.

Recently RTL-SDR.COM reader António submitted a link to an interesting project called "MySondy" which is created by Mirko Dalmonte (IZ4PNN). MySondy is custom firmware for TTGO Lora32 433 MHz boards which allows them to be turned into a radiosonde tracker. A TTGO is a cheap ~US$20 LoRa32 IoT dev board with an onboard WiFi + Bluetooth enabled ESP32 microcontroller and OLED display. Some of the slightly higher priced units come with a built in GPS receiver as well. With the custom firmware it is capable of receiving and decoding common radiosonde protocols such as RS41, M10, RS92 and DFM.

A TTGO ESP32 LoRa Board
A TTGO running MySondy firmware enclosed in a 3D Printed Case

There is also an Android App called MySondy Go and MySondy FINDER which connect to the TTGO via Bluetooth. This app plots the location of the radiosonde on a map, allowing you to easily follow and track down the balloon. You can also go to mysondy.altervista.org to see public MySondy stations. Clicking on a blinking dot will connect you with the MySondy server, allowing you to see tracked sondes.

MySondy Web Interface

The firmware and software appear to be fairly new, so there isn't much information about this that we could find just yet. Also we note that all manuals and information about the project is written in Italian, except for a French magazine article (pdf) that António sent us to upload.

We note that these TTGO ESP32 LoRa boards are quite interesting by themselves, with other custom firmware available to do things like create a Paxcounter which counts the number of mobile devices in an area via WiFi and Bluetooth signals, and the ability to use them as a GPS enabled Mesh network based text message radio.