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Old June 2nd 18, 10:10 PM posted to aus.radio.amateur.misc,rec.radio.amateur.digital.misc,rec.radio.amateur.equipment,rec.radio.info
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Default [FOAR] The Internet of Digital Radio


Foundations of Amateur Radio

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The Internet of Digital Radio

Posted: 02 Jun 2018 10:00 AM PDT


Foundations of Amateur 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...
This posting includes a media file:
http://podcasts.itmaze.com.au/founda...teur-radio.mp3


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