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
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.
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 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.
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.
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.
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.
The SDR-Kits L-band Patch antenna is a modified GPS antenna designed for receiving Inmarsat satellite stations such as AERO and STD-C. They have another version for receiving Iridium frequencies as well. The patch costs £12.90 inc VAT in UK, or approx US$14 for non-UK customers.
Over on his channel Frugal Radio has uploaded a video where he tests this patch antenna with an RTL-SDR Blog V3. The built in bias tee on the V3 is used to power the antenna. In the video he shows how he's able to receive and decode AERO using the JAERO decoding software and how he uses a a metal backing to improve reception.
Over on Facebook Job Geheniau has recently been sharing how he's taken an image of our galaxy (the Milky Way) with a radio telescope consisting of a 1.5 meter dish, RTL-SDR and a few filters and LNAs. In the past we've posted several times about others observing the Hydrogen line with an RTL-SDR, and we have a tutorial here showing how to observe it on a budget.
In this case, Job went a step further than just a single measurement. He used a used a motorized dish and RTL-SDR to scan the entire Milky Way over one month, resulting in a full radio image of the galaxy. As his posts and pdf document are on Facebook and not visible to those without Facebook accounts, we asked for permission to reproduce some of them here for all to see. We have also mirrored his PDF file here, which contains more information about his radio telescope, results and setup.
To make a very long story short. After a month of angel patience (and that says something to me) I managed to take a 'picture' of our entire galaxy (galaxy) in neutral hydrogen! I attach some pictures. If you are more interested, please come after this and PDF with explanation. It was a hell of a job I can tell you. But here's the ' picture s' of the house (230 million light years wide) in which we live and in which we all have a big mouth......
Hydrogen Line Image of the Milky Way produced by Job Geheniau
For the Scientists among us... a beautiful plot of the Milky Way Graphically explained in neutral hydrogen....... In short, summarized... if you look up on a beautiful summer evening you will see a beautiful galaxy, this is graphically the same but then on a different frequency than the eye can perceive. own dates of course.....
A composite of Hydrogen Line readings at different points of the Milky Way produced by Job GeheniauAn image of the Galactic Plane (longitude 20 to 240 steps of 5 degrees and latitude 0)
His setup consists of a 1.5m dish, extended to 1.9m with some mesh. A 1420 MHz tuned feed, Mini Circuits ZX6-P33ULN LNA, Bandpass Filter, NooElec SAWBird LNA, Bias-T, RTL-SDR V3, PST Rotator Dish Software, VIRGO software, SDR#, Cartes due Ciel sky chart and a home made netfilter.
He uses a modified version of the VIRGO software to read sky coordinates from a text file, and this points the telescope at each predefined coordinate. He then uses VIRGO to record data for 180 seconds before moving on to the next coordinate. The data is then plotted in Excel, and the highest peak is taken at each coordinate and put back into an 8x21 matrix in excel. Conditional formatting is then used to generate a color gradient resulting in a rough map. Then a Gaussian blur is applied, and it is projected over the Galaxy, resulting in the images above.
The Hydrogen Line is an observable increase in RF power at 1420.4058 MHz created by Hydrogen atoms. It is most easily detected by pointing a directional antenna towards the Milky Way as there are many more hydrogen atoms in our own galaxy. This effect can be used to measure the shape and other properties of our own galaxy.
