D Star emulation.

[Tom Azlin N4ZPT]

Hi Alex

On 5/16/2011 11:06 PM, Alex Fraser wrote:
> I've heard they have a USB dongle that does D Star from a computer. It's rather
> pricey. Can the D Star format be done in software emulation? Can the SDR's do D
> Star?

D-STAR has a mixed voice and slow data mode that uses the DVSI AMBE chip 
for its CODEC and sends out the mixed voice/data stream at 4800 bps 
using GMSK modulation.  The USB Dongle, aka DVDongle, includes the AMBE 
CODEC chip.  Only pricey given low production volume and all the stuff 
that has to wrap around the $20 DVSI chip. some hams that do not have a 
nearby D-STAR repeater use this to connect into one.  Others use this to 
monitor their repeater when they travel. Creater of this dongle had to 
reverse engineer the protocol to get his device to work properly. But 
then since he is the author of the major add on software for the 
repeaters he had a good head start on that.

You can get software that works with the DVDongle that lets you connect 
to D-STAR repeaters or reflectors.  You can get 3rd party software that 
uses the DVDongle as the voice encode/decode and your computer soundcard 
to generate the GMSK signal then pipe that into the 9600 bps port of a 
VHF or UHF radio.  Say your 706.

So yes, you can do GMSK and the D-STAR framing in software but you can 
not do the CODEC in software. There is a team trying to write an 
unencumbered CODEC that can be used in an alternate standard but it is 
not there yet. ( "CODEC2").  But it will never play with the radios that 
have the DVSI AMBE chip.

The other D-STAR mode is a data only mode that transports tcp/ip at up 
to 128 kbps using GMSK. Only radio so far is a Icom radio that is on 
23cm and runs at 128 kbps. Myself and a bunch others have been using 
these radios in public service events for about 5 years now. You could 
use a USRP and the rig RF hardware to roll your own.

You can confirm the above with some searches of the web. this has been a 
discussion several years long now in the community playing with this.

73, tom n4zpt