Rich Freeman on 15 May 2019 17:57:13 -0700

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Re: [PLUG] PLUG Fusion room or DMR Talkgroup

On Wed, May 15, 2019 at 7:39 PM Keith C. Perry
<> wrote:
> Like an amateur radio beginner's talk specially on digital modes?  That could be interesting considering many of the hotspots are pi-star based and RPi's are a thing. :)

Keep in mind that digital modes are WAY more diverse than DMR, D-star,
and Fusion.  CW is arguably a digital mode.

Right now we're mostly talking about digital voice mode, not unlike
what cell phones do.  Voice goes into a vocoder which generates
packets of data, which then get transmitted using FSK/TDMA/etc
(details vary by mode), with usually around 12.5kHz bandwidth I think.

But, there are plenty of pure-data digital modes used on HF with much
lower baud rates mainly used to send text, like PSK31 which uses only
60Hz bandwidth, which is much less than CW/Morse.

And of course right now we're mostly talking about setting up the
networked groups online, so you get the vocoding and the packets, but
they're sent out over UDP to some server not unlike any random voice
chat application.  They're just using the same internal format as the
over-the-air protocol so they're trivial to bridge to a repeater.

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