Tag: opulent-voice

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Inner Circle Newsletter December 2024

Welcome to Open Research Institute’s Inner Circle Newsletter for December 2024. We have a lot to share with you!

Open Research Institute is a non-profit dedicated to open source digital radio work. We do both technical and regulatory work. Our designs are intended for both space and terrestrial deployment. We’re all volunteer. You can get involved by visiting https://openresearch.institute/getting-started

Membership is free. All work is published to the general public at no cost. Our work can be reviewed and designs downloaded at https://github.com/OpenResearchInstitute

We equally value ethical behavior and over-the-air demonstrations of innovative and relevant open source solutions. We offer remotely accessible lab benches for microwave band radio hardware and software development. We host meetups and events at least once a week. Members come from around the world.

Read on for regulatory, technical, and social articles. We close with a calendar of recent and upcoming events.

Want to subscribe to the Inner Circle? Sign up at http://eepurl.com/h_hYzL

Previous issues of Inner Circle can be found at https://www.openresearch.institute/newsletter-subscription/

Regulatory Work at ORI

Making Open Source Easier for Everyone

Past regulatory work at ORI can be found at https://github.com/OpenResearchInstitute/documents/tree/master/Regulatory

219 MHz Project

by Mike McGinty

Federal Communications Commission License DB (FCC LicDB) is a set of tools for exploring the FCC license database dumps. The tools are at https://github.com/tarxvftech/fcc_licdb

These database dumps are at https://www.fcc.gov/wireless/data

What you see in FCC LicDB is a way to download and then import most of the weekly database dumps to an sqlite database. Expect a couple gigabytes for uls.db, depending on how many services you import.

After that, the purpose of this repository gets more esoteric because it’s less about exploring and more about answering. (Answering what?)

There’s a problem with the 219-220 MHz amateur band. 47 CFR part 80 defines this band (among others) as for Automated Maritime Telecommunications Systems (AMTS), but that idea completely failed and so now there are no AMTS stations, just companies licensed for AMTS, usually through leases, that use the spectrum for other purposes.

The restrictions on Amateur secondary use of the band defined in part 97 were designed for a world where AMTS stations were on the coast. This, along with other circumstance, define the problem that exists today – it is nearly impossible to operate an Amateur radio on the band despite hams deliberately being given the spectrum.

See https://github.com/tarxvftech/47CFR for more details on this situation. I started this LicDB repo to figure out where these AMTS licensees operate, and what they are using it for. The ULS database interfaces available to the public are not sufficient for answering questions like this (details in W5NYV’s first talk “The Haunted Band”).

But where a generic system may struggle, a more targeted approach can solve.

What you see below is a functionality-first view of the FCC licensing system mapping as much of the AMTS stations licensed or operating in the 219-220MHz band as can be found in the database.

It’s not perfect – working on data from other people and systems that you have no control over never is – but it’s much better than all existing alternatives.

Other Projects

It’s expected this would be useful for redoing W5NYV’s exploration into the demographics of Amateur Radio operators in the US: https://github.com/Abraxas3d/Demographics

Similarly, it might be very interesting to plot ALL the LO, PC, and other entries, and then merge in the other data that isn’t in the FCC database, like ham radio repeaters, to try to make the radio services in the ether around you that much more legible.

Some entries are not easy to import into the database, or have data errors that make them difficult to plot on the map. Those entities are not presently accounted for.

Above, AMTS stations in the United States. Below, a few detail images from the map, which can be found at https://amts.rf.band (heavy data, be patient for first load).

An article from ORI called “Space Frequency Block Coding Design for the Neptune Communications Project” will be in the January-February 2025 issue of QEX Magazine, from ARRL. Thank you to ARRL for publishing open source work from ORI.

Article Summary

The article discusses the design and implementation of Space Frequency Block Coding (SFBC) in the Neptune Communications Project, a digital radio initiative operating at 5 GHz for amateur radio applications.


Key Concepts and Objectives:

SFBC is a technique used in digital communications to improve signal resiliency by leveraging spatial, frequency, and coding diversity. It is commonly implemented in systems using Orthogonal Frequency Division Multiplexing (OFDM), utilizing multiple antennas for diversity. The mathematics are explained step-by-step with diagrams and equations. Noise calculations worked out in an Appendix.


Amateur Radio Application:

The Neptune project focuses on transmitting robust digital signals in noisy environments, essential for drone and aerospace communications. SFBC increases the likelihood of data recovery by mitigating multi-path interference and improving signal-to-noise ratio (SNR). An open source OFDM modem is needed in amateur radio.


Technical Details


Implementation:

SFBC transforms transmitted signal samples mathematically before sending them via two transmit antennas. Multi-path and spatial diversity enhance signal integrity against environmental reflections and interference.


Operation:

Signals are transmitted using OFDM, where subcarriers provide frequency diversity. The encoding does not increase throughput on its own but makes it easier to achieve maximum throughput performance.


Coding techniques like the Alamouti scheme are explained, with diagrams, for creating and decoding signals.


Trade-offs:

SFBC reduces SNR by 3 dB compared to optimal techniques like Maximum Ratio Combining but avoids the need for channel state knowledge at the transmitter.


Practical Implementation:
SFBC was modeled and tested in MATLAB/Simulink, with plans for FPGA and ASIC implementations.


Future work includes:

Expanding to Space Time Block Coding (STBC).

Live demonstrations of SFBC/STBC performance differences.

Open-source release of HDL source code for hardware implementations.


Call to Action:

The Neptune project is a volunteer-driven, open-source initiative under the Open Research Institute (ORI). Community participation is encouraged, providing educational and developmental opportunities in digital communication technologies.

Watch Dr. Marks explain the RFBitBanger project and the SCAMP protocol in this video at https://www.youtube.com/watch?v=Fbgs_4QsKnE

And then… let us tell you that SCAMP is now in FLDigi!

SCAMP is now even easier to use. If you want to get involved with this new mode and also build your skills with a very special low power HF radio kit, please visit our eBay listing for kits at https://www.ebay.com/itm/364783754396

A Tale of Troubleshooting

Problem Solving our Minimum Shift Keying Implementation in the Lab
by Team OPV

Minimum shift keying (MSK) is the modulation used by Opulent Voice, our open source uplink protocol for our space and terrestrial transceiver. Unlike some other modulations, there aren’t a lot of documented and working examples of MSK, despite the many advantages of using this modulation for space and terrestrial channels. One of our educational goals at ORI is to provide exactly that, a documented and working example of MSK, that also delivers useful functionality to the amateur radio satellite service. 

In the process of writing down a description of what happens mathematically, so that software defined radios like the PLUTO SDR can transmit and receive our Opulent Voice protocol, there’s been quite a few troubleshooting sessions. One session solved a problem where the main lobe bandwidth was too large. Another session solved a problem where the processor side code didn’t properly configure the radio chip. Another session switched to the correct version of LibIIO, or Library of Industrial Input and Ouput routines. The wrong library meant that the radio was “sort of” working, but not completely. 

Troubleshooting and debugging systems is where most volunteer engineering time is spent. This is no different from professional development, where blank-paper time spent writing down routines may be a small fraction of the total development time of a project.

It can take multiple attempts to solve a problem. When this happens, it’s important to back up completely and recheck basic assumptions. Looking at the images below, one can see the desired MSK spectrum at the top. On the bottom is an example of an undesirable spectrum. The main lobe is bifurcated and the sidelobes have extra power. If you look at the graph, you can see that the sidelobes are higher in the “bad” example than they are in the “good” example. These are all clues, and there are several ways to go about attempting to solve the problem. The bad or “split” spectrum seemed to show up at random times, but it would go away when new PI controller gain pairs were written to the radio. 

Why were we writing new proportional and integral gains to the radio? We were trying to tune our PI Filter, which is in the Costas Loop, which is in charge of tracking the frequency and phase of our signal so we can demodulate and decode successfully. We wrote code to search through proportional and integral gain pairs, testing their performance both in digital loopback and in loopback over the air.

After reviewing the code, asking for help, getting a variety of good advice, and trying to duplicate the problem in MATLAB, the problem unexpectedly went away when the processor side code was updated to remove extra writes to MSK block configuration registers.

The lessons learned?

* Clean code that matches the design of the hardware may prevent unexpected behavior. Don’t be sloppy with your test code!

* Keep up to date on changes in register accesses and behavior. There was a change from setting and clearing a bit in a register to the bit being toggled. This was a change from the level being important to the change in the level being important. Do your best to match what’s in the hardware! 

Below, the “bad” spectrum as observed in the lab.

Below, the “good” spectrum, which returned after what we thought were unrelated code changes.

Opulent Voice at University of Puerto Rico

An Educational Success Story

by Michelle Thompson W5NYV with Oscar Resto KP4RF

Oscar Resto is an Instrumentation Specialist at the University of Puerto Rico’s Department of Physics. He also serves as the Principal Investigator for the university’s RockSat-X program. RockSat-X is a highly-regarded and very successful educational program sponsored by NASA and the Colorado Space Grant Consortium at the University of Colorado at Boulder. RockSat-X offers university and community college teams the opportunity to develop experiments for suborbital rocket flights, fostering innovation and practical experience in space-related fields.

Beyond his academic roles, Oscar is active in the amateur radio community, holding the call sign KP4RF. He has been involved in initiatives such as renewing the Memorandum of Understanding between the ARRL Puerto Rico Section and the American Red Cross Puerto Rico Chapter and has presented to a wide variety of audiences about amateur radio and emergency communications during and after major hurricanes. 


The University of Puerto Rico has actively participated in NASA’s RockSat-X program since 2011, providing students with hands-on experience in designing, fabricating, testing, and conducting experiments for spaceflight. UPR’s RockSat-X team has developed increasingly complex experiments over the years. In 2011, UPR’s inaugural RockSat-X project utilized mass spectrometry to analyze atmospheric particles and pressure. Subsequent payloads have continued to evolve and refine the investigation of the “middle atmosphere”, an often-overlooked layer in atmospheric studies. 

Oscar’s engineering design philosophy is to put the program in the hands of the students. The students are fully involved from the beginning of the process until launch. Oscar supports and enables consistent student success in two ways. First, by using the Socratic method of asking questions to lead the students through the many stages of design, test, documentation, and build. Second, by communicating clear expecatations about process and deadlines. Students source parts, build components using a wide range of manufacturing processes, and program all of the control and embedded devices. They carry out testing at the component, module, and end-to-end systems level. The student interface with NASA through meetings and regular reports.  


Recent missions included deploying sterilized collection systems into the space environment to gather organic molecules, such as amino acids, proteins, and DNA, from altitudes between 43 to 100 miles above Earth. To ensure the integrity of collected samples, the team implemented innovative decontamination procedures that were carried out in flight.

For the 2023 and 2024 UPR RockSat-X entry, Opulent Voice was included as a communications payload. That version was a 4-ary FSK modulation, voice only, and ran on a general-purpose processor. In 2023, the rocket experienced a failure. In 2024, the mission was a complete success, with Opulent Voice received on a student-built and crewed portable station near the launch site. For 2025, assuming UPR’s RockSat-X application is accepted by NASA, the Minimum Shift Key (MSK) version of Opulent Voice, implemented on an FPGA and deployed on a PLUTO SDR, will be used by the student build team. This MSK version is much more advanced and more spectrally efficient.

Review the MSK version at https://github.com/OpenResearchInstitute/pluto_msk
See an image of the student poster presentation about the 2024 UPR RockSat-X project below. 

Shipment was delayed, but a nice surprise for Ribbit has finally arrived. Below is the plaque for Ribbit’s 2023 Technical Innovation Award.

The metal surface has black lettering and an image of a laptop computer. The body of the plaque is a handsome hardwood.

The text reads “For developing the Ribbit app for Android and iOS devices. The innovative and open-source Ribbit app allows amateurs to utilize audio from amateur radio transceivers such as VHF/UHF handhelds to send and receive text messages across the devices. The Ribbit app leverages OFDM technology currently used in cellular 4G and 5G networks & WiFi.”

Below, the plaque hanging on the wall in Remote Lab West.

Remote Labs are test benches with spectrum analyzers, oscilloscopes, power and frequency meters, FPGA development stations, power supplies, and multiple SDRs. The equipment is supported by a computer running virtual machines with a variety of operating systems to support software, firmware, and hardware development. Remote Labs are available 24 hours a day, 365 days a year for open source development. 

Thank you to Pierre and Ahmet for all the extremely hard work to make Ribbit so successful!

Learn more about Ribbit and try out the web app at https://www.ribbitradio.org

Geometry Puzzle

Given a 3, 4, 5 right triangle, with an inscribed semi-circle, where the hypotenuse of the triangle bisects the circle to form this semi-circle, find the area of this semi-circle.

Spoiler! The worked-out solution by Paul Williamson KB5MU is below.  

The Inner Circle Sphere of Activity

December 17-22 2024 – Open Research Institute participates on the Federal Communication Commission’s Technological Advisory Council (TAC). Working groups composed of volunteers from industry, academia, and open source (ORI) meet weekly and debate and deliver advice to the FCC quarterly. This hybrid meeting is streamed on the FCC website. 

December 31, 2024 – Fiscal year ends for Open Research Institute. Work begins on filing 2024 IRS 990 returns, which are due May 15, 2025.

December 20, 2024 through January 6, 2025 – Holiday Break for all labs and teams. 

March 6, 2025 – Open Research Institute celebrates another birthday with parties planned so far in the US, Canada, and Europe. Sign up for a fun day commemorating open source volunteers around the world by writing hello@openresearch.institute.

Thank you to all who support our work! We certainly couldn’t do it without you. 

Anshul Makkar, Director ORI
Frank Brickle, Director ORI
Keith Wheeler, Secretary ORI
Steve Conklin, CFO ORI
Michelle Thompson, CEO ORI
Matthew Wishek, Director ORI

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400 Subscriber Milestone on YouTube

Thank you to everyone reading this that has supported ORI and how we publish our work on YouTube.

I know YouTube is not for everyone, but it is an effective way to communicate what we do, what challenges we face, and it lets people know there’s a community out there 1) doing things that they might find wonderful and 2) is worth hearing more about.

We have 400 subscribers, which is a bit of a milestone. This is a lot for a very technical all-volunteer organization that devotes its time supporting and promoting project work, while staying firmly in the background.

Our proudest moments are when projects succeed and are recognized on their own merits, under their own name, and under their own branding. Ribbit, RFBitBanger, Haifuraiya, a variety of published Open Source FPGA work, FPGA training, Opulent Voice, Versatuner, Dumbbell, actively participating in IEEE, FCC TAC membership, Remote Labs, our many regulatory successes, and our active and successful mentoring in professional and academic settings – these are all clear indications that we’re on the right track and doing a great job.

Not explicitly mentioned are the many places we’ve helped projects succeed behind the scenes, around the world.

We are committed to an altruistic approach that delivers clear value to project work. This approach has been abused only once, by one organization.

Being accountable, open, and successful is the cost of doing our type of business. This is a price happily paid.

Thank you for being part of it!

https://www.youtube.com/c/OpenResearchInstituteInc

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Updating the Opulent Voice Interleaver

The interleaver for Opulent Voice needs to be updated because the frame size has increased. We are incorporating RTP, UDP, and IP layers into the existing OPUS and 4-ary MFSK layers and now have what we think may be the final frame size.

Since convolutional encoding is used for Opulent Voice payload, an interleaver is necessary to get the best bit error rate performance out of the convolutional encoder. The interleaver is used over both the physical layer header (Golay encoded) and the data payload (a 1/2 rate Convolutional code). Opulent Voice is an open protocol that we use for our HEO/GEO uplink. It can also be used terrestrially on the #hamradio bands at 70cm and above. Find out more at https://www.openresearch.institute/2022/07/30/opulent-voice-digital-voice-and-data-protocol-update/

The distance that an interleaver spreads out bits in a frame is the most familiar performance measurement. It’s commonly called “spread” or “minimum interleaved distance”. However, we learned about another metric that is important in Turbo codes. Several papers refer to the measure of randomness of the mixture of bit position reassignments as “dispersion” (for example, see https://cgi.tu-harburg.de/~c00e8lit/cgi-bin/ivpub/download.php?file=kb-wpmc2008.pdf). That particular paper cited another paper (reference [6]) as defining dispersion.

Following that citation lead to a paper but this paper didn’t mention dispersion or explain the equation. Going back to the original paper, we started working with the definition for dispersion that we had. This used the cardinality of the set of indices of original bit positions vs. permuted bit positions. This seemed straightforward enough. But, after trying this in MATLAB, we always got the minimum dispersion value, so there must be something wrong with our interpretation.

Volunteers then spent time trying to figure out if dispersion is important enough metric for a single convolutional code, like we have in #OpulentVoice. In other words, should we simply not simply choose the polynomials that result in the largest minimum interleaved distance? Selecting the right interleaver based on a balance between how far apart it spreads the bits vs. how randomly the bits are distributed is a useful selection methodology for Turbo codes, but may not be strictly necessary for a single convolutional code used with 40 mS frames.

Everyone is welcome to join in the discussion and work to create quality #OpenSource work for #digital communications at ORI. Please see https://openresearch.institute/getting-started to be welcomed to our community.

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Inner Circle Newsletter February 2023

Greetings all! Welcome to the February 2023 issue of the Inner Circle Newsletter from Open Research Institute.

Join the Inner Circle

Sign up for this newsletter at http://eepurl.com/h_hYzL

Thank you so much for your time, attention, and support. We appreciate you, we welcome your feedback, and we are dedicated to serving the community to the best of our abilities. You can get in touch with the ORI board of directors directly at hello@operesearch.institute.

A Puzzle Just For Fun

Here’s a puzzle. Chicken Nuggets have been on the menu at the international fast food chain McDonald’s since 1983.

If Chicken McNuggets are sold in packs of 6, 9, or 20, then what is the largest number of nuggets that cannot be ordered?

Answer is at the end of this newsletter!

Projects

Our volunteer teams have been busy and successful, and our project lineup has grown.

Regulatory Efforts: ORI works hard to promote and defend open source digital radio work. We do all we can to help move technology from proprietary and controlled to open and free. Our work on ITAR, EAR, Debris Mitigation, and AI/ML are where we have spent most of our time over the past two years. We were a member of the Technological Advisory Committee for the US Federal Communications Commission in 2022, and co-chaired the Safe Uses of AI/ML Subworking Group. We have received consistently positive reviews for all of our work, and there has been increasing use of the results.

Ribbit: this open source communications protocol uses the highest performance error correction and modern techniques available to turn any analog radio into an efficient and useful digital text terminal. No wires, no extra equipment. The only thing you’ll need to use it is the free open source Android or IoS app on your phone. Learn how to use this communications system and get involved in building a truly innovative open source tactical radio service by visiting https://ribbitradio.org

Join Ribbit mailing lists at: https://www.openresearch.institute/mailing-lists/

Amateur Satellite: ORI has the world’s first and only open source HEO/GEO communications satellite program, called Haifuraiya. We will demonstrate all working parts of the transponder project at DEFCON 31, where broadband digital communications and open source electric propulsion will be featured. Find out how to support or join this and other teams at https://openresearch.institute/getting-started

AmbaSat for 70 cm: We’ve redesigned the AmbaSat board to move it from 915 MHz to 70 cm and it will be flown on a sounding rocket this year. With increasing interest in LoRa for both space and terrestrial use, this has proven to be a popular and useful project. The design has been adapted for applications in India and Japan.

Opulent Voice: a digital protocol that seamlessly combines high fidelity voice and data, using modern forward error correction, authentication and authorization, and efficient minimum frequency shift keying modulation. Opulent Voice will be flown on a sounding rocket this year and it is the native digital uplink protocol for Haifuraiya. Completely open with the high quality voice we deserve to hear. Due to the bandwidth requirements of the 16kHz OPUS codec, Opulent Voice can be used on 70cm and above ham bands, or anywhere else where the modest bandwidth requirements can be met.

Remote Labs: We have two remotely accessible workbenches for FPGA development, with Xilinx 7000 and Xilinx Ultrascale+ development boards as the focus. We also have several SDRs and radio utility devices available through virtual machine access. The 7000 series development board has an Analog Devices ADRV9371 radio system attached, and that has enabled a number of open source FPGA products to be published. This is a unique resource that has produced a lot of good work and is constantly being improved and updated. In addition to the development boards, the laboratory has a network accessible spectrum analyzer, an oscilloscope with logic analyzer extension, power supplies, frequency and power counters, and dedicated human resources available to help students, volunteers, or professionals contribute to open source work. Help it be more useful by spreading the word about ORI Remote Labs.

Equipment available: https://github.com/phase4ground/documents/tree/master/Remote_Labs/Test_Equipment
How to get an account: https://github.com/phase4ground/documents/blob/master/Remote_Labs/ORI-New-User-Setup.md
Using FPGA Development Stations: https://github.com/phase4ground/documents/blob/master/Remote_Labs/Working-With-FPGAs.md

Versatune: amateur digital television next generation hardware and software product. It is open source and affordable. We have committed engineering resources to support Versatune and are very excited about how things are going. Some of the Versatune team will be at Hamvention 2023 in Xenia, OH, USA, and it will be represented at DEFCON in August 2023.

HF antennas: We have a novel foldable antenna design for space and terrestrial use. The hardware prototype will be demonstrated at DEFCON. This design manipulates radiation resistance to produce best-of-class results. Think you can’t do 160m without an enormous antenna? Think again.

HF QRP: Coming soon, an exciting HF QRP digital radio board and protocol. The hardware prototypes will be demonstrated at DEFCON. What might happen when we combine the HF digital radio with the novel foldable antenna? We think you’ll be delighted.

Battery Matching Curves: are you available to mentor a college student interested in learning how to match up charge and discharge curves from NiCd cells in order to create battery packs? These packs would then be tested and/or deployed in the field. Our student volunteer has collected the data and is looking to learn how to use Jupyter Notebooks to select the cells to create battery packs.

Logistics

We’re growing and adapting!

We will be changing our GitHub project name from Phase4Ground to Open Research Institute very soon. Phase4Space GitHub project will change to Haifuraiya, which is the program name for our HEO/GEO design. These changes better reflect the content and purpose of the 64 repositories that span everything from important historical archives to open source music to the most modern open source encoders available.

We have a very well-qualified applicant for our open board of directors position. We would like to invite interested community members to consider applying to ORI in order to expand the board beyond this filled position in order to take us from our current five members to seven. Given our continuing growth, a larger leadership team would ensure continued smooth operations. These positions are unpaid, engaging, and can be demanding. The most important skill set is a strong sense of ethics and service.

Fundraising and Grants

We’ve applied for the GitHub Accelerator Program (Remote Labs) and the IEEE Innovation Fund (Polar Codes in Ribbit). If you have a recommendation for ORI in terms of partnerships or collaboration, please let us know at hello@openresearch.institute

Support ORI financially directly through the website https://openresearch.institute. There is a PayPal donation widget at the bottom of almost every page. Donations can be directed to any project, or to general operations. ORI has a very low overhead, with most projects coming in under 5%.

Support our open source propulsion work and get a cool desk toy at https://us.commitchange.com/ca/san-diego/open-research-institute/campaigns/where-will-we-go-next

We’ve raised enough money to cover materials for machining the engine parts. The next step is to raise enough money to pay for the electronics. Please help spread the word!

Thanks to our wonderful community, we have employee matching in place at Microsoft and Qualcomm. If you have an employee matching program at your work, and you think ORI would fit in, please consider nominating us. Our EIN is EIN: 82-3945232

Events

Where can you meet up with ORI people?

QSO Today Ham Expo

We support and attend QSO Today Ham Expo, held online 25-26 March 2023. The theme of this event is “New License, Now What?” and focuses on people new to amateur radio.

Our page for QSO Today Ham Expo content is https://www.openresearch.institute/qso-today-ham-expo-technical-demonstrations/

IMS2023

Join us at the amateur radio social at the International Microwave Symposium (IMS2023) on Tuesday 13 June 2023 in San Diego, CA, USA at 6pm. It will be held in a beautiful outdoor venue with food and drink provided. The easiest way to register for this event is to purchase an exhibition badge and then sign up for the social. https://ims-ieee.org/ is the event website.

DEFCON

We are getting ready for our biggest event of the year. We have proposed an in-person Open Source Showcase to RF Village for DEFCON 31 in Las Vegas, Nevada, USA from 10 – 13 August 2023.

Our page for the event, with all the latest and greatest details, can be found at https://www.openresearch.institute/defcon/

Want to help at DEFCON? Please visit https://openresearch.institute/getting-started and let us know!

IWRC 2023

IEEE wants to bring together all participants to take full advantage of CHIPS Act funding. IEEE will have an Innovative Workforce Resources Conference in Little Rock, AR 13-14 September. There will be a reception at the Clinton Presidential Library, and attendees will enjoy the best BBQ in the country. The National Science Foundation requires that a certain percentage of funding has to be spent in states that don’t get their fair share of research money. The goal of this conference is to pull together small researchers from small business like ORI and do research, with Arkansas as a focus.

We couldn’t agree more. After all, we are putting a lot of time and energy into Remote Labs South, located just outside Little Rock, AR. Bringing innovative open source digital radio work to students, workers, and volunteers that need it the most simply makes sense. If you can attend IWRC 2023 and help represent ORI please get in touch. We will be reaching out to IEEE chapters in Arkansas as well.

Read about the CHIPS and Science Act here: https://en.wikipedia.org/wiki/CHIPS_and_Science_Act

Puzzle Solution

43 is the largest number of nuggets that cannot be ordered.

What is the largest number of McNuggets that you can’t buy with packs of 6, 9 and 20? After putting in their blood, sweat, and tears, the mathematicians found that the answer is 43. You cannot buy 43 nuggets with packs of 6, 9 and 20, but you can buy any amount larger than 43.

Please see Mike Beneshan’s excellent blog about this type of problem at https://mikebeneschan.medium.com/the-chicken-mcnugget-theorem-explained-2daca6fbbe1e

The other Non-McNugget numbers are 1,2,3,4,5,7,8,10,11,13,14,16,17,19,22,23,25,28,31,34, and 37.

Trivia: You can get 47 in two ways: 36+19+120 or 06+39+120.

We’ve used the McDonald’s version of the chicken nugget to present and frame this mathematical puzzle. Here’s a link about the history of this menu item: https://www.thrillist.com/news/nation/history-of-chicken-mcnuggets

Robert C. Baker invented the chicken nugget, among many other things. He was a true innovator of what can be fairly called “modern foods”. A brief wikipedia article about him can be found here: https://en.wikipedia.org/wiki/Robert_C._Baker

A song written about this remarkable inventor can be enjoyed at this link: https://youtu.be/OEa8wqv4QM0

Do you have an idea for an interdisciplinary puzzle for our next newsletter? We’d love to hear about it. Write ori@openresearch.institute

Until Next Time

Thank you so much for being part of our Inner Circle! You are the motivation for all of this work, provided to the general public for free. We believe it makes the world a better place.

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Inner Circle – September 2022

Greetings from Open Research Institute!

We hope to see you again at QSO Today Ham Expo this weekend, 17-18 September 2022. We have a booth, five talks, three project exhibits, and a lounge space for meet and greet.

To find out more about Ham Expo, visit https://www.qsotodayhamexpo.com/

Since the last Ham Expo, we’ve integrated the DVB-S2/X encoder into the downlink reference design for our open source broadband microwave transponder. We have started on the uplink receiver. We have published a specification for our high bitrate digital voice and data uplink protocol. It’s called Opulent Voice and it will be introduced and described at the Expo. Find the source code for a C++ implementation at https://github.com/phase4ground/opv-cxx-demod

We have two sounding rocket projects, an open source propulsion project, successful regulatory work, and we represent open source and amateur radio interests on the US FCC Technological Advisory Committee. We co-chair the “Safe Uses of AI/ML” subworking group.

Our open source HEO proposal Haifuraiya will be presented at the Expo this weekend and details will be in an upcoming JAMSAT Journal.

We do terrestrial communications as well! Ribbit is a digital emergency communications mode for VHF/UHF. No extra equipment or cables required. We have a poster about the project in the exhibit hall and a presentation. Get the free Android application at https://play.google.com/store/apps/details?id=com.aicodix.rattlegram

All video presentations will be available at our YouTube channel after the Ham Expo platform has closed in 30 days.

We have a mailing list for updates and discussion, a Slack account for engineering work, and all work is published as it is created to our GitHub account.

To join any of these resources at ORI, please visit https://www.openresearch.institute/getting-started/

If you’d like to get monthly newsletters like this one, then do nothing. You’re already part of the inner circle!

Our volunteers could not accomplish all of this wonderful work without your interest and support.

Thank you from everyone at ORI. We value your comment, critique, and feedback, and look forward to hearing from you. If you use social media, then a lot of what we do is published through the channels linked below.

Thank you from all of us at ORI!

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Deviation Limits of the MD-380

Not enough deviation for Opulent Voice

We measured the deviation limits on the MD-380 with firmware from OpenRTX. Thank you to Redman for help with modifying the firmware to make this test as easy as possible.

The transmitted signal is about 10 dB down at 3000 Hz and almost gone at 4200 Hz. Therefore, there is not enough deviation for Opulent Voice.

The part of the radio under test was the HR_C5000. This is a part from Hong Rui and is a DMR digital communications chip. The chip handles 4FSK modulation and demodulation, among other functions.

According to a translated datasheet for the HR C5000, adjustment of the frequency offset range not possible. It appears to be designed only for +/- 3 kHz. Unless there’s an undocumented feature, or gain is added after the HR C5000, then +/- 3 kHz is the maximum deviation for this radio.

The HR C5000 puts out two analog signals MOD1 and MOD2, which are combined and then drive a varactor diode. The varactor might well have more range. Or it could be replaced with one that has more range.

Below is a photo essay of the testing and screenshots of results.

30 AWG wire soldered to pin 5 of the HR_C5000 on the MD-380. This is one of two audio inputs to the modulator. It’s the one used for signaling tones, and not the one used for microphone audio, in the original design. Ground wire attached as well and brought out. Firmware modifications disabled M17 baseband output when PTT pressed. Pre-emphasis and filters disabled by putting radio in M17 mode. The red wire is part of the standard M17 mod for the MD-380.
Ground wire attached to point on board and brought out. Modifications inspected by KB5MU in Remote Lab.
The black rubbery weather seal gasket around the perimeter of the cast heatsink means there’s no way for wires, even very skinny ones, to come out through the seam in the case.
Hole was drilled in the side of the case and the wires brought out. Radio was put back together. Battery, display, etc. all working after modifications. Notice the 20 dB attenuator on the output of the HT. Its lowest output power is 1W nominal, which matches the maximum rated input of the spectrum analyzer, so the attenuator was added to protect the spectrum analyzer’s front end.
Test setup.

Test Results

Transmitted signal before modified firmware.
Transmitted signal after modified firmware. Notice no modulation because the baseband signal has been disabled.
1kHz sine wave at 100 mV injected to pin 5 of the HR C5000.
1kHz sine wave at 220 mV injected to pin 5 of the HR C5000.
3 kHz sine wave at 220 mV injected to pin 5 of the HR C5000. Signal is about 10dB down at 3 kHz
4200 Hz sine wave at 220 mV injected to pin 5 of the HR C5000. Signal is approximately 45 dB down.
Looking at the low end, this is one half a Hz at 220 mV injected to pin 5 of the HR C5000.
Two tenths of a Hz at 220 mV injected to pin 5 of the HR C5000. Notice the discontinuities. These were not seen when the signal generator was connected to an oscilloscope. It could be that when the modulating frequency is too low, it interacts with a PLL or other frequency stabilization loop in the radio.
It would not be an issue in the original design, with all audio coupled through capacitors. No way anything that close to DC would get to the audio chip.
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Opulent Voice – digital voice and data protocol update

This Opulent Voice sticker is available from ORI at events around the world.

Opulent Voice is an open source high bitrate digital voice (and data) protocol. It’s what we are using for our native digital uplink protocol for ORI’s transponder project. Opulent Voice is also looking pretty darn good for terrestrial.

Here is an audible example of the Opulent Voice audio quality under ideal conditions. Each file is about 37 seconds long. It starts with a short musical intro, and the rest is the beginning of the audio track from one of Michelle’s conference talks. These were originally recorded with mid-range podcasting studio gear. The recording was converted to a signed 16-bit PCM raw file, which has been re-converted to a standard WAV file so you can play it easily, MDT-short.wav

Original recording


This file was then run through opv-mod to create a file of baseband samples, which was then piped to opv-demod, which created an output file of signed 16-bit PCM. That file was converted to WAV file MDT-short.demod.wav

Original recording modulated and then demodulated through Opulent Voice.


We expect to present a nice demo at DEFCON in August 2022 and at the QSO Today Ham Expo in September 2022.

We’ll be using COBS protocol within Opulent Voice. If you’re unfamiliar with COBS, please read about it here: 

https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing

Authentication and authorization is built in and optional. There is no separate “packet mode”. Things are designed to “just work” and get out of your way whether or not you’re sending voice or data. 

Opulent Voice is designed to where you can use even higher bitrate OPUS codecs if you wish. This will most likely be a build option and not a run-time option, but if a run-time option is something you want to work on, speak up! Let’s see what we can accomplish.

Originally based on Mobilinkd codebase that implements M17, the Opulent Voice development implementation can be found here:

https://github.com/phase4ground/opv-cxx-demod

Initial demos will be on a HackRF/PortaPack on the 1.2 GHz ham bands. 

Thank you to OpenRTX for help with troubleshooting the audio quality on the PortaPack. In order to have a good demo, basic FM transmit from the microphone needs to work. The audio quality is pretty bad (this was a surprise) with the stock application, so we’ve been spending some time with the Mayhem codebase, the microphone transmit app, and the driver for the audio codec in order to get it sounding like it should. This needs to happen before we publish an app for the PortaPack. 

Synthesized audio from the HackRF/PortaPack sounds clear and wonderful. It’s just the microphone that is splattery and overdriven. 

ORI’s Slack channel can be found at https://phase4ground.slack.com/

The authentication and authorization work is in #aaaaa
Opulent Voice work is in #opulent-voice

Thank you to everyone supporting the work!

-Michelle Thompson