{ "id": 361, "date": "2022-02-14T10:22:27", "date_gmt": "2022-02-14T10:22:27", "guid": { "rendered": "https:\/\/www.poliham.polimi.it\/?p=361" }, "modified": "2022-02-18T15:27:52", "modified_gmt": "2022-02-18T15:27:52", "slug": "free-software-free-radio-experimentation", "status": "publish", "type": "post", "link": "https:\/\/www.poliham.polimi.it\/en\/?p=361", "title": { "rendered": "Free Software Empowers Radio Experimentation" }, "content": { "rendered": "

The advent of digital modes radically changed the way we experience ham radio, the digital transport of voice allows to interconnect stations from all over the world through the internet. If on one hand the physical distance between places is no more a limit, the correct configuration of the radio has become a true challenge. In particular, the commercial nature of the most common digital modes, the technical complexity combined with a lack of information, and the legal and patent restrictions on the voice encoding technology hampered the experimentation on digital modes, constraining it to either simple use or limited interconnection experiments.<\/p>\n\n\n\n

However, this landscape will soon change, the rising M17 protocol<\/a> is estabilishing itself as an open source and community driven alternative to pre-existing digital modes. M17 is developed by hams for hams, it's transparent and well-documented, and embodies the open source vocoder codec2. <\/em>Corrently, however, there are no commercial radios able to module the M17 protocol, even if there are many community-developed alternatives such as TNC3<\/a>, M17Client<\/a> and Module 17<\/a>, notwithstanding the possibility of modulating<\/a> and demodulating<\/a> usinng a PC and an SDR.<\/p>\n\n\n\n

The availability of infrastructure creates a strong drive to the adoption of new technologies. Curently the last firmware release of the MMDVM platform<\/a> natively supports M17, this allows to easily create M17-enabled repeaters, or to make pre-exising repeaters M17-capable, in fact M17 is expected to be correctly modulated by MMDVM system already capable of modulating DMR<\/a>.
The protocol, however, is still is its initial growth phase, where few people have access to a compatible device, thus few repeater operators invest in repeaters and hotspots supporting M17.<\/p>\n\n\n\n

A way to break this loop could be to adapt a commercially available low-cost radio to the M17 protocol. Currently this option is made available by the OpenRTX open source firmware for TYT MD380, MD390, MD-UV380, MD-UV390 and clones. These radio, however, leverage a discrete baseband, optimized for the DMR protocol which cannot be easily adapted to different protocols. OpenRTX, to modulate M17, needs to give the radio microcontroller direct access to the radio microphone, speaker and baseband signals. On MD3x0 and MD-UV3x0 these paths are not present and need to be created through a hardware modification.<\/p>\n\n\n\n

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Picture of a TYT MD-380 running the OpenRTX firmware in M17 mode<\/figcaption><\/figure><\/div>\n\n\n\n

OpenRTX allows then to use a radio which costs less than a hundred euros, to modulate a protocol which the radio was not originally built to modulate. This allows, in theory, to implement any other potocol which fits the modulation bandwidth of the original baseband, everything implemented in software in the radio's own microcontroller. It will be thus possible to implement the transmission and reception of various protocols, such as: APRS, SSTV and P25.<\/p>\n\n\n\n

The availability of a low-cost portable radio on which you can run your own code, enables a new way to enjoy ham radio, in which it is no more necessary to possess the latest radio model to be able to experiment. A way in which ideas and work from the individual can be shared to the whole community. An example of a community-sourced feature is the Low Earth Orbit (LEO) tracking with doppler correction, available in OpenRTX, implemented by Mike McGinty<\/a>.<\/p>\n\n\n\n

OpenRTX LEO satellite tracking demo<\/figcaption><\/figure>\n\n\n\n

Experimentation does not end with the radio itself, but can be extended to the whole ecosystem. Since protocol, repeaters, and radios are community-driven, nothing prevents to create auto-discovery<\/em> systems for the available repeaters, Over-The-Air (OTA)<\/em> firmware upgrade through data-mode download from the repeater, picture and audio recordings exchange, dynamic interconnection right from the radio menu. The posibilities are endless.<\/p>\n\n\n\n

And where software-only<\/em> implementation won't be enough, we will make it through the creation of customized radio platforms. The use cases for a hardware device are several, from portable radios, to mobile radios, to repeaters, to Internet of Things<\/em> modems. The OpenRTX project is currently developing a small modem board modem to be integrated with expansion cards into all the aforementioned use cases. The project is named RadioCard<\/a> and will be build in the M.2 form factor, commonly used in laptop SSD and Wi-Fi and WWAN modems.<\/p>\n\n\n\n

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Initial rendering of the M.2 RadioCard module, developed by OpenRTX<\/figcaption><\/figure><\/div>\n\n\n\n

This huge experimentation potential can spur interesting innovation, able to change and expand the way we experience ham radio. In this community-driven process, the individual interests and abilities can converge into a greater goal, giving to everybody the chance to express their skills<\/em> at best. At the same time, such an heterogeneous project has no rigid boundaries between disciplines, consequently it allows everyone to expand their views and to study and learn new abilities.<\/p>\n\n\n\n

If you're interested to the project, here are a few ways to get in touch:<\/p>\n\n\n\n