[Dstar] D-Star Digital Data

[Andrew Gilbett]

2009/9/2 Tony Langdon <vk3jed at gmail.com>:
> Currently, DD is supported only on 23cm.  There is no 70cm equipment.

That's fair enough.

> There is no "low bandwidth DD mode", there is only DD (128 kbps on 23cm) and
> DV, which is simultaneous voice and data totalling 4.8 kbps.

Upon re-reading the specifications I now see that ;-)
Which explains your next comment!

> DV mode is simultaneous voice and data, so it's the same thing.  DV contains
> the following:
>
> 2.4 kbps voice, with 1.2kbps FEC (total 3.6 kbps).
> Headers and other protocol overheads
> Low speed data stream (no error correction) available for user applications.



> Interesting thesis. :)

I hope so!! Got 10 months of it to go, don't want it to become boring :p

> Well, the utility of mixed mode repeaters is questionable, because of the
> informal nature of amateur communities.  There might be some circumstances
> where they'll fit in, but the key problem is the FM users not conflicting
> with the D-STAR users and vice-versa.  Amateurs are used to being able to
> hear all traffic on the frequency and join in when they wish to.  However,
> being able to convert the repeater from FM to D-STAR and back, manually,
> could be useful.

That is a fair call, I have some idea's but until I have completed
some experimentation (so that I know what I'm talking about...) I am
not planning on discussing them in microscopic detail on a public
forum. Though I am anticipating that the outcomes of this
experimentation will be up for discussion.

> Building a D-STAR software defined repeater is entirely feasible, as you
> basically need to perform GMSK modulation and demodulation, and the rest is
> pushing data bits around.  With D-STAR, the RF side is only half the story,
> there's also the Internet infrastructure, which provides the long haul links
> between sites. :)

Got the RF side worked out, as you say it is feasible. Still reading
the manuals on  the gateway systems! But if you have more info on how
the Gateway system works that would be good!

Thanks
Andrew
VK2XAG