I was not trying to start a D-STAR discussion! I was simply saying that there are 4800 bps GMSK sound card modems being worked on and pointed to the groups where that discussion is underway. Ignore the protocol and content and look at the modem design in software. Then go from there.
D-STAR DV has already been used via satellite and it worked fine is what I understood. But was just an experiment not a proposal for a new satellite mode.
73, Tom n4zpt
Art McBride wrote:
D-Star protocol is 4.8kb/sec for voice 1.2 kb for FEC and 1.2kb for data. It is GMSK data, transmit rate is 3.6KHz max transmission rate, (7.2kb NRZ), deviation is 1.8 KHz for a modulation index of 0.5. BW per Carlson's rule is 7.2 KHz A vocoder module provides for the voice compression. The Data side is used for Call Sign, Name, City/ State, Brag Tape, GPS position, and Texting all done with voice simultaneously. D-Star is not very successful in mobile operation. I have had lots of conversations go R2D2 from a truck or car passing me. From a fixed position range is surprisingly good. When used on a Satellite this narrow mode I suspect is very sensitive to Doppler as well as multipath. Circular antennas on both ends will solve multipath, but Doppler shift must be dealt with. Art, KC6UQH
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Nathaniel S. Parsons Sent: Saturday, April 10, 2010 10:02 PM To: Tom Azlin N4ZPT Cc: AMSAT-BB Subject: [amsat-bb] Re: BeeSat at 4800 GMSK
Ah, thanks for clarifying. Unfortunately, if I understand you correctly, we would have to talk to our satellite via digital voice, or at 128kbps, which would be great if we could!
-Nate
On Sat, Apr 10, 2010 at 10:15 PM, Tom Azlin N4ZPT n4zpt@cox.net wrote:
Well, make that the digital voice part of the protocol. The high speed digital data part is up to 128kbps which was not what I was thinking of.
73, tom n4zpt
Tom Azlin N4ZPT wrote:
Hi Nate,
the D-STAR protocol is only GMSK at 4800 bps and they selected a time-bandwidth product of 0.5. 4,800 bps or 4k8 is perhaps not talked
about
as that IS the standard for D-STAR. So the software there might be adaptable. that is the reason I thought to suggest it.
Good luck and 73, Tom n4zpt
Nathaniel S. Parsons wrote:
Hi Tom,
My mind had indeed played a trick on me, and I remembered MFSK as MSK.
As far as the DStar group goes, I don't see any mention of 4800 bps or 4k8 kbps on the public page, so if it's not the group's focus, I don't want to have to rely on that solution.
Thanks, -Nate KC2SVI
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