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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