The Exemplar of Open Research and Development
An open source Low Density Parity Check decode from Phase 4 Ground is working for DVB-S2, DVB-S2X, and DVB-T2 in GNU Radio, thanks to the efforts of Ahmet Inan, Ron Economos, and Charles Brain.
This is a big step forward for open source satellite communications.
Video report here:
https://youtu.be/fOYVOgybFKY
Out of Tree (OOT) GNU Radio module by Dr. MPEG here:
https://github.com/drmpeg/gr-dvbldpc
Decoder by Ahmet here:
https://github.com/xdsopl/LDPC
Here’s a demonstration of a 3D printed Cassegrain antenna system for 122GHz amateur radio. It was presented in the demonstration room at Microwave Update 2018.
122 GHz is an amateur radio band. There’s activity and distance records and some contesting. 122GHz has significant attenuation due to atmospheric absorption. Specifically, oxygen gets in the way.
I’ve been working on a 3D printed rig for 122GHz. This was sparked by a request from Alan Devlin VK3XPD for a 3D printed subreflector for a Cassegrain dish. People generally get by with a flat subreflector, but you can get better performance if it’s a hyperbolic curve matched to the feed and parabolic dish.
So what is 122GHz good for? Well, car radar for one thing. That’s what Silicon Radar does. They’re a company in Germany, and they have a radar development board and Millimeter Wave Integrated Circuits (MMICs) for 122GHz. The patch antennas are actually on the chip. The dev boards were used in this experiment. They send out a wide chirped radar signal and measure the return. There is software provided by Silicon Radar that runs the dev board.
The goal for Microwave Update 2018 was to verify a 3D printed Cassegrain antenna design for 122GHz amateur use. This design was adapted from the Customizable Cassegrain dish by drxenocide on Thingiverse. Link is in the show notes. https://www.thingiverse.com/thing:1935824
This thing creates a customizable Cassegrain Reflector dish. It was created using the equations from the paper by Peter Hannan, “Microwave antennas derived from the Cassegrain telescope,” in IRE Transactions on Antennas and Propagation, vol. 9, no. 2, pp. 140-153, March 1961.
The antenna parts were designed, the 3d model specified, the parts were printed, the resulting pieces were metallized (with MG Chemicals conductive paint), and then the parts combined into their final form.
Design files and papers can be found here: https://github.com/Abraxas3d/122GHz
The assemblies were taken to Microwave Update 2018 and set up in the demonstration room. Here’s what happened next.
So what were the results? Here’s some screenshots from the Silicon Radar software with and without the Cassegrain antenna installed over the stock lens in the development board.
And, there’s more. Please read Mike Levelle’s wonderful report on his efforts with the Silicon Radar chip in building a simple 122GHz transceiver. Link is in the show notes.
Mike has a tremendous amount of expertise and enthusiasm for the higher microwave bands and is a fantastic mentor.
http://www.bay-net.org/docs/k6ml-122GHzradio-baycon2018.pdf
What’s next? Building a radio! Stay tuned and stay on the air!
Bruce Perens was the keynote speaker at the Open Source CubeSat Workshop 2018 in Madrid, Spain.
Michelle Thompson presented a technical update on Phase 4 Ground activities and described recent progress with DVB-S2X receivers in GNU Radio.
Held at the European Space Astronomy Center in late September 2018, the conference drew 122 diverse and enthusiastic participants from 22 countries. Two days of presentations and workgroups resulted in a remarkable amount of progress and sharing in support of open source spacecraft and ground stations.
Below are links to notes from the four working groups in which Phase 4 Ground volunteers participated.
Open Source Satellites – Improving the Starting Point
SatNOGS Report and Discussion
Libre Cube Standard, Community Development
Hugh’s Blog Post
Links to video recordings of presentations will be released soon.
Amateur Radio and open source Amateur Satellite activities at this past week’s DEFCONwere very successful.
Multiple talks across the somewhat daunting schedule provided plenty of opportunities to hear about amateur radio, open source satellites, modulation and coding, and ground station work. Phase 4 Ground had an opportunity to present at Cyberspectrum, and then helped host a Q&A the following day.
Open Research Institute had a booth in the WiFi Village Friday-Sunday. Services provided were the DEFCON ham radio license exam information/encouragement, SatNOGS information/handouts/stickers, Libre Space Foundation information/handouts/stickers, GNU Radio demonstrations and quick tutorials, FaradayRF information/handouts, SDR demonstrations, Trans-Ionospheric badges, Phase 4 Ground updates/recruitment/promotion, and more.
The landscape of amateur radio in space is diverse, interesting, and active. The audience at DEFCON is enthusiastic, positive, technical, and generally unafraid to build things and try stuff.
The Amateur Radio Relay League (ARRL) was there this year, and they are thinking about coming to GNU Radio Conference as well.
We met several university researchers and put them in touch with the right support networks to get their cubesats “off the ground”.
It’s hard work to be part of a event as large, loud, and busy as DEFCON. The attendance was estimated at 27,500 by Sunday. However, it’s very much worth it! It was great to meet so many people in person for the first time that we’ve gotten to know through electronic means.
We are solidly in the black on Trans-Ionospheric badge sales and are well on our way to funding the development board for Phase 4 Ground radios. Support and information here: https://www.openresearch.institute/badge/
We’ll be selling them online shortly. All proceeds go directly to support the non-profit ORI, and specifically for Phase 4 Ground project.
Next up: finding out how to improve representation for amateur radio on interplanetary missions from NASA. We’ll be at the Interplanetary Cubesat Workshop this week at Goddard Space Flight Center. We’ll have a poster session on open source satellite and ground station work, specifically allowed under ITAR 120.11.
Thank you to everyone that helped make this trip rewarding and fun with the encouragement, support, and materials.
Hello everyone,
GNU Radio Conference is coming up in September. If you haven’t registered and want to go, please do at https://www.gnuradio.org/grcon-2018/
There’s a special event this year called Block Party.
It’s an effort to get DVB-S2 and DVB-S2X receivers in GNU Radio.
We will have our own room and tables and swag. We will have docents enthusiasm and test equipment. We’re looking for more! We’ll have documentation and refreshments.
We need blocks!
Most blocks needed for DVB-S2/X receive do, in some form, already exist. Some do not. Some just need additional modulation and codings added to them.
Receiver design is hard, but breaking it up into small blocks makes it tractable.
The DVB protocol documents are all open. There are implementation guidelines. See https://www.dvb.org/
There are several community members that are experts in this area. There is a team (Phase 4 Ground – find out more at https://phase4ground.github.io/) that needs DVB-S2/X to work in GNU Radio. There is a lot of interest from a variety of other groups including Libre Space, ARRL, AMSAT, and TAPR.
If you are able to contribute to this effort, I want to know about it! I am here to support it. I’d like nothing better than to complete the Block Party at GNU Radio Conference with working, tested, documented blocks for a DVB-S2/X receiver. This contribution makes our open source terrestrial and space radio designs for Phase 4 Ground possible, and also opens up a lot of other work.
The thing that is considered the hardest part is the LDPC FEC decode. We have an open source implementation that targets GPUs. We want to take this and get it into RFNoC. If you are working on this as well, we want to collaborate and support and combine and promote.
The GPU implementation (by Charles Brain G4GUO) of LDPC decode can be found at our repository folder here: https://github.com/phase4ground/DVB-receiver/tree/master/G4GUO-LDPC-on-GPU/DVB-S2XTxRx
Phase 4 Ground is devoted to an open source implementation of DVB-S2 and DVB-S2X for amateur radio terrestrial and space use. We are part of Open Research Institute. Learn more about this non-profit here: https://openresearch.institute/
Here’s an update from the lab on correlator troubleshooting. We are trying to get correlation understood and under control over the air.
We have two flowgraphs that we believe aren’t working due to the Correlation Estimation Issue here https://github.com/gnuradio/gnuradio/issues/1207
We don’t think it’s operator error, but we’re relatively new to GNU Radio, and would welcome any comment or critique that helps to solve this!
FM_ARAP_to_downlink.grc is the flowgraph we are using for transmit side.
What does it do?
It collects up four analog FM channels, digitizes, and transmits a time division multiplexed signal out. This is, in general, a simple model of our uplink for a Groundsat or payload.
We see the expected transmitted signal on a spectrum analyzer and on a HackRF portapack and on the receiving system across the lab.
The receiving flowgraph is called TDM_downlink_rx.grc
What does it do?
It takes the time division multiplex signal and is supposed to break the channels back out.
This demo has worked in the past, but not anymore, and definitely not over the air now.
The problem seems to be the correlator, and it seems to be the same trouble reported in the issue.
We want to write a DVB-S2/X correlator. I think we can also help fix this correlation estimation block. In all cases, we want to comply with the tag scheme produced, so that downstream blocks already in GNU Radio get what they’re expecting, if they are expecting these types of tags.
Plenty more at https://github.com/phase4ground
Tickets available now!
https://www.gnuradio.org/grcon-2018/
Our booth will show projects associated with Palomar Amateur Radio Club, the AMSAT Member Society Open Research Institute‘s Phase 4 Program, GNU Radio , FaradayRF, and will host the first Trans-Ionospheric electronic badge sales.
Open Research Institute (ORI) is a non-profit research and development organization which provides all of its work to the general public under the principles of Open Source and Open Access to Research.
ORI includes Phase 4 Ground, an open source amateur radio project primarily intended for AMSAT. Our goal is to provide both designs and equipment for a radio that will operate with a 5GHz uplink and a 10GHz downlink. Our mission is to provide an open source implementation of DVB-S2 and DVB-S2X for both satellite and terrestrial amateur radio use. The reference design will be in GNU Radio, and a variety of radio recipes will be published. These solutions range from DIY to something you can purchase off-the-shelf. Phase 4 Ground radios are intended to be reusable and reconfigurable, supporting payloads at GEO (Phase 4B), HEO (Phase 3E), and beyond (Cube Quest Challenge). Additionally, these radios will work as terrestrial microwave stations. Groundsats on mountaintops or towers establish a fun and flexible digital microwave experience.
GNU Radio is a free & open-source software development toolkit that provides signal processing blocks to implement software radios. It can be used with readily-available low-cost external RF hardware to create software-defined radios, or without hardware in a simulation-like environment. It is widely used in research, industry, academia, government, and hobbyist environments to support both wireless communications research and real-world radio systems.
Faraday is more than just another Industrial, Scientific, and Medical band transceiver (ISM). Faraday takes advantage of the ISM hardware which works on the amateur radio 33cm band to let us focus on the real tasks we want to accomplish. The FaradayRF Master Plan details these tasks of which providing a well documented and educational digital wireless ham radio platform enabling an infrastructure to be built from is among the first goals. 500mW at 915MHz packs the power necessary to traverse over 40km required by last-mile communications infrastructure. The on-board Antennova M10478-A2 GPS adds location aware applications out of the box without the need for additional hardware. Overall, Faraday was designed to provide access to 33cm to radio amateurs and empower them to experiment and learn. A stronger ham radio is a more exciting ham radio.
Tickets are available now at http://hamvention.org/purchase-tickets/