Category: Applications

DSD (Open Source) with dPMR Decoding and Windows Binaries Released

Digital Speech Decoder (DSD) is an open source program for decoding signals containing digital speech, such as DMR and P25. The open source version has been mostly surpassed in use over the last few years by the closed source DSD+ version. However, work is still ongoing on the open source version, and a recent fork by Louis-Erig HERVE @LouisErigHerve has added support for Digital Private Mobile Radio (dPMR) decoding.

dPMR is an open, non-proprietary trunked radio standard that supports both data and digital voice transmission. A licence free variation for short range communications called dPMR466 uses the 446.1–446.2 MHz band. Other modes allow for efficient peer to peer to peer operation (mode 1), operation with a base station repeater (mode 2), or with a trunking signal (mode 3).  All dPMR signals operate in FDMA mode with an efficient bandwidth of only 6.25 kHz. dPMR is also known as Icom IDAS and Kenwood NEXEDGE.

Code for Louis-Erig's DSD fork can be found on his GitHub, and he has also released binaries for Windows on his website. Over on his Twitter he has also been mentioning that he has been able to get around the basic privacy modes on DMR.

dPMR radios, data stations and repeater hardware.
dPMR radios, data stations and repeater hardware.

DragonOS: DSP and Signal Analysis with Composable-SDR, Inspectrum and an RTL-SDR

DragonOS is a ready to use Linux OS image that includes various SDR programs preinstalled. The creator Aaron also runs a YouTube channel that contains multiple tutorial videos for DragonOS

One of the latest videos shows us how to use composable-sdr and Inspectrum to capture and analyze signals. Both programs are pre-built into the latest version of DragonOS. Composable-sdr is a set of DSP processing blocks for SDRs embedded in Haskell. One thing it does well is allowing users to easily capture and record demodulated signals for later use via the terminal. Inspectrum is a tool for analysing and reverse engineering signals that have been recorded.

In the video Aaron explores many of the composable-sdr examples discussed on it's GitHub readme page. Including analyzing a wav file recorded with Composable-sdr with Inspectrum and demodulating and recording a wideband FM signal. He also mentions how it's possible to create a PMR446 scanner that records up to 16 channels at once, and how decode helicopter FSK data from audio heard on YouTube (which we mentioned in a previous post).

DragonOS LTS DSP and signal analysis with Composable-SDR + Inspectrum (RTL-SDR)

Tech Minds: Testing the OpenEar DMR TETRA ADSB POCSAG Decoder for RTL-SDR

Back in March we posted about the release of OpenEar, a standalone TETRA decoder for the RTL-SDR. Since then OpenEar has undergone massive developments, not only improving upon the TETRA decoder, but adding DMR, ADS-B and POCSAG decoders as well as a waterfall display.

Recently Tech Minds reviewed this software on his YouTube channel. In the video he shows how to download the software, install the rtlsdr.dll file, and run and use the software. He then demonstrates reception of an amateur radio DMR repeater, reception of POCSAG pager messages and finally reception of ADS-B aircraft messages.

OpenEar Digital Decoder - DMR TETRA P25 ADSB POCSAG RTL-SDR

Building a Remote SSB Receiver with an RTL-SDR, OrangePi and GNU Radio

Over on his blog F1ATB has uploaded a post explaining how he created an RTL-SDR or HackRF based remote SSB receiver controllable with an internet browser. To set this up he uses an Orange Pi One Plus single board computer which runs several GNU Radio based digital signal processing flow graphs. Then a Python server serves a custom HTML and Javascript based web interface with waterfall that can be controlled remotely over the internet. In the post he explains the GNU Radio DSP flowgraphs that he's built, and notes that he will explain the HTML and Javascript side in another future article.

The SSB receiver block diagram
The SSB receiver block diagram

Talks from the 2020 HamSCI Convention (Held Online)

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". Recently they held their HamSCI 2020 workshop online, and the videos are now available on the Ham Radio 2.0 YouTube channel. Several of the projects mentioned in the talks involve the use of software defined radios.

Come join HamSCI at its third annual workshop! Due to restrictions caused by the COVID-19 Coronavirus, this year's workshop will he held as a virtual, eletronic workshop. The meeting will take place March 20-21, 2020 using Zoom Webinar Services hosted by The University of Scranton in Scranton, PA . The primary objective of the HamSCI workshop is to bring together the amateur radio community and professional scientists. The theme of the 2020 HamSCI Workshop is "The Auroral Connection: How does the aurora affect amateur radio, and what can we learn about the aurora from radio techniques?" Invited speakers include Dr. Elizabeth MacDonald, NASA Scientist and founder of Aurorasaurus, Dr. James LaBelle, Dartmouth Space Scientist and expert on radio aurora, and Dave Hallidy K2DH, an expert in ham radio auroral communication.

One talk discusses the HamSCI personal weather station project, which is an SDR and Raspberry Pi based solution that monitors HF signals like WSPR, as well as characterizing HF noise, detecting lightning and ionospheric disturbances.

HamSCI 2020 Overview of the Personal Space Weather Station and Project Update

Another talk discusses the TangerineSDR, which is an open source SDR currently in development by TAPR. The goal of the TangerineSDR is to be a sub $500 SDR with a focus on space science, academic research as well as general amateur use. 

HamSCI 2020 TangerineSDR Data Engine and Overall Architecture

The rest of the talks can be found on the Ham Radio 2.0 YouTube playlist.

A Talk on 21cm Hydrogen Line Amateur Radio Astronomy

The Amateur Radio Experimenters Group (AREG) recently held an online talk with guest speakers Phil Lock and Bill Cowley, talking about amateur radio astronomy. In the talk they note how they use an RTL-SDR as their radio.

Cheaper electronics has created great possibilities for Amateur Radio Astronomy. This talk will describe a local project to receive and map the distribution of 1420 MHz signals from neutral hydrogen in our galaxy. We briefly describe the history of 21cm RA and why it’s still of great interest to astronomers. We outline some challenges over the last few years in assembling a 2m dish with custom feed, electronics and signal processing, then show recent results from our project.

The image in the thumbnail shows recent signals (May 17th) recorded over a 24 hour period for dish elevation of 53 degrees. The signal changes as the antenna points to different parts of the Milky Way.

https://www.areg.org.au

The World of Amateur Radio Astronomy - Listening to the Galaxy

Open Weather: An Artistic Performance Involving Live NOAA APT Signal Decoding for Sound Arts Festival

Just after our post a few days ago about an art project involving weather satellite reception with SDRs, we received a story submission about an artistic performance with similar weather satellite and SDR themes. The submission from Sasha Engelmann reads:

Open Work, Second Body is a live-streamed performance by designer Sophie Dyer (@sophiecdyer) [M6NYX] and geographer Sasha Engelmann (@sashacakes) [M6IOR] in collaboration with the author Daisy Hildyard. The work was performed twice during Reveil 2020, a global sound arts festival streaming sounds from listening points around the planet on the day of the International Dawn Chorus.

Open Work, Second Body asks: From the climate crisis to coronavirus: what are the tools we need to make sense of events unfolding on vastly disparate scales? Through spoken word, field recordings and live radio reception of two NOAA satellite images, the work probes the porous boundaries between our bodies, local atmospheres and weather systems.

Still image capture from livestream of Open Work, Second Body, AM performance, May 2nd 2020

Due to lockdown constraints in London, Sophie and Sasha were not able to be in the same place or to leave their apartments, so they performed the work via simultaneous streams from their respective balconies in South East and North West London. Using RTL-SDRs, Turnstile antennas, Open Broadcast Software and collaborating with two NOAA satellite passes, Sophie and Sasha shared the process of decoding NOAA satellite images with hundreds of viewers around the world, employing spoken word poetry and field recordings to complicate relationships of local and global, weather and climate, the individual and the collective. 

Recordings of the performances can be found at the links below. 

☀️Morning: https://youtu.be/-5JrxwNpJqI [performance starts at 05:25]
?️ Afternoon: https://youtu.be/h88zaCtX8cw [performance starts at 05:00]

Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020
Still image capture from livestream of Open Work, Second Body, PM performance, May 2nd 2020

Open Work, Second Body is part of Sophie and Sasha's larger artistic research and design project Open Weather, which employs ham radio, open data and feminist theories and approaches to build new and diverse communities around satellite image decoding and weather sensing. The Open Weather web platform will be launched in Summer 2020 and will host an archive of SDR-generated weather images, visually rich how-to guides for those with no radio and engineering experience, and material about Sophie and Sasha's collaborative artistic practice. 

For Open Work, Second Body, Sophie and Sasha would like to thank the Soundcamp Team: Grant Smith, Dawn Scarfe, Christine Bramwell, Maria Papadomanolaki and Ciara Drew. They are grateful to Daisy Hildyard for her willingness to be in conversation with them, Bill Liles NQ6Zfor technical advice, Jol Thoms for sound design, Rachel Dedman, Laure Selys and Arjuna Neuman (Radio Earth Hold) for early curatorial input, Akademie Schloss Solitude for the support of a residency, the satellites NOAA 18 and NOAA 19 and the RTL-SDR and wider ham radio community. 

http://www.sophiedyer.net

http://www.sashaengelmann.com

It's very cool to see technical hobbies like ours starting to make an impact in art and reaching a wider audience. More content and images available on Sophie's Open Weather webpage, and Sasha's Open Weather webpage. 
Open Weather Live Stream

Understanding, Listening and Recording Trunked Radio Systems with an RTL-SDR and Trunk-Recorder

Trunked radio systems for voice communications can be easily found when browsing the spectrum with an SDR. Listening to a voice communication is easy, but actually following a conversation along is almost impossible to do manually. This is because in a trunking system the frequency in use during a conversation can change often. The frequency of the voice is dictated by a control channel that all radios listen to. This allows multiple talk groups (Police, EMS, business etc) to share one chunk of the spectrum without having to allocate fixed channels for each user.

Over on his blog Andrew Nohawk has uploaded an excellent guide that explains trunked radio, how it works, how to use radioreference to look up trunked radio frequencies in your area, and how to use an RTL-SDR to listen in. He then shows how to use a program called "trunk-recorder" which will automatically record and upload trunked radio conversations to a site like openmhz.com for sharing. 

Voice Trunking Seen on GQRX with an RTL-SDR
Voice Trunking Seen on GQRX with an RTL-SDR