Foundations of Amateur Radio The Internet of Digital Radio The topic of how radio evolves and embraces available technology is one that describes the hobby itself. From spark-gap through AM, SSB and FM our community picked up or invented solutions to make communication possible. When the internet came along it too became a tool ripe for picking and in 1997 a connection between a radio and the internet was made with the Internet Radio Linking Project or IRLP when Dave VE7LTD, a student at the University of British Columbia, joined the UBC Amateur Radio Society. Using a radio, some hardware and a computer, you could send audio between radios across the internet. Since then this field has exploded with D-STAR, Echolink, DMR, AllStar, Wires, CODEC2, System Fusion and Brandmeister. At a glance they're all the same thing, radio + internet = joy. Looking closer there are two distinct kinds of internet radio contraptions, those where the radio is digital and those where it's not. IRLP is an example of an analogue radio connecting to hardware that does the encoding into digital and transmission across the internet. At the other end the reverse process, decoding, happens and another analogue radio is used to hear the result. This encoding and decoding is done by a piece of software called a CODEC. If we continue for a moment down the analogue path, Echolink, AllStar and Wires do similar things. In 2002 Echolink made its way onto the scene, similar to IRLP, but it didn't need any specialised hardware, any computer running the Echolink software could be used as both a client and a server, that is, you could use it to listen to Echolink, or you could use it to connect a radio to another Echolink computer. AllStar, which started life in 2008 went a step further by making the linking completely separate. It uses the metaphor of a telephone exchange to connect nodes together, which is not surprising if you know that it's built on top of the open source telephone switching software Asterisk. In 2012 or so, Yaesu introduced Wires which is much like Echolink and AllStar. There are servers with rooms, not unlike chat rooms, where you connect a node to and in turn your radio. Blurring the lines between these technologies happened when you could build a computer that spoke both IRLP and Echolink at the same time. Now you can also add AllStar to that mix. Essentially these systems do similar things. They manage switching differently, handle DTMF differently, use a different audio CODEC and handle authentication in a variety of ways, but essentially they're ways of connecting normal hand-held radios, generally FM, to each other via the internet using intermediary computers called nodes. Before you start sending angry letters, I know, there's more to it, but I've got more to tell. While Dave was busy in Canada inventing IRLP back in the late 1990's, in Japan the Ministry of Posts and Telecommunications funded research, administered by the Japan Amateur Radio League into the digitisation of amateur radio. In 2001 that research resulted in what we know today as D-STAR. Two years later, ICOM started developing D-STAR hardware which resulted in actual physical radios less than a year later. Today you can get D-STAR hardware from ICOM, Kenwood and FlexRadio Systems. Unlike the other technologies where the audio was converted at a central place, in D-STAR the audio is encoded in the radio and a digital signal is sent across the airwaves. That in turn means that the software that does the encoding, the CODEC, needs to be inside the radio. Since the information is digital right from the point of transmit, you can send other information, like GPS locations and messages along with the audio. In 2005 DMR started life as a group of companies, now up to around 40, agreeing on some standards for digital audio in much the same way as D-STAR. Mostly in use by commercial users, DMR has the ability to have two users simultaneously on-air using alternate channels by having separate time slots for each channel, alternating between the two of them. They agreed to use the same CODEC to ensure compatibility. Formal interoperability testing has been happening since 2010, but because DMR allows manufacturers to build in extra features many brands cannot actually work together on the same network. For many years D-STAR and DMR-MARC, the DMR Motorola Amateur Radio Club World Wide Network, were the main digital radio systems around in amateur radio. That changed in 2013 when Yaesu introduced System Fusion. It too made digital audio at the radio, but it added a wrinkle by making it possible to have both analogue and digital audio on the same repeater. Depending on how the repeater is configured, analogue and digital radios can coexist and communicate with each other. The Wires system that Yaesu rolled out was upgraded in 2016, renamed to Wires X and now also incorporates digital information to allow the linking of their System Fusion repeaters. In 2014 at the Ham Radio Exhibition in Friedrichshafen in Germany, Artem R3ABM planned to make an alternative master server for DMR+ and DMR-MARC and the result was a German wordplay which we know today as Brandmeister. It acts as a network for digital radios in much the same way as DMR, but it's run as an open alternative to the commercially available options made by Motorola and Hytera. The story isn't complete without mentioning one other development, CODEC2. It started in 2008 when Bruce Perens K6BP contacted Jean-Marc Valin, famous for the SPEEX audio compressor and David Rowe VK5DGR about the proprietary and patented nature of low data use voice encoders such as those in use in D-STAR, DMR and System Fusion. David had already been working in this area a decade earlier and started writing code. In 2012 during Linux Conference Australia, Jean-Marc and David spent some time together hacking and managed to make a 25% improvement and CODEC2 was well under way. Today CODEC2 forms the basis of several projects including FreeDV in software, the SM1000 FreeDV adaptor in hardware and the roadmap for the future of open and free digital voice is bright. I should mention that this information is specifically brief to give you an overview of the landscape and hopefully I've not made too many glaring errors, but feel free to drop me a line if you do find a problem. Digital radio and the internet, it's not just a single mode, a whole cloud of modes, and I haven't even started with WSPR, FT8 or JT65. I'm Onno VK6FLAB To listen to the podcast, visit the website: http://podcasts.itmaze.com.au/foundations/ and scroll to the bottom for the latest episode. You can also use your podcast tool of choice and search for my callsign, VK6FLAB, or you can read the book, look for my callsign on your local Amazon store, or visit my author page: http://amazon.com/author/owh If you'd like to participate in discussion about the podcast or about amateur radio, you can visit the Facebook group: https://www.facebook.com/groups/foundations.itmaze Feel free to get in touch directly via email: firstname.lastname@example.org, or follow on twitter: @VK6FLAB (http://twitter.com/vk6flab/) If you'd like to join the weekly net for new and returning amateurs, check out the details at http://ftroop.vk6.net, the net runs every week on Saturday, from 00:00 to 01:00 UTC on Echolink, IRLP, AllStar Link and 2m FM via various repeaters.