[amsat-bb] Re: BeeSat at 4800 GMSK

[Mike Rupprecht]

Hi Nate,

Sorry for the long delay....

MixW doesn't support GMSK. You mix that with MFSK.

BeeSat has two CMX909B modems (CML) onboard. The data is sent in the MOBITEX
format, not AX.25 !
See here for more information about Mobitex:
http://en.wikipedia.org/wiki/Mobitex

The CMX909B is a half-duplex Gaussian Minimum Shift Keyed (GMSK) BT = 0.3
modem data pump with on-chip packet data handling. GMSK modulation optimises
the data throughput for a given bandwidth RF channel and the on-chip packet
data handling relieves the host µC of regular processing tasks, such as
maintaining Bit and Frame Synchronisation, Block Formatting, CRC and FEC
Error Processing, Data Interleaving and Scrambling. 

73, Mike
DK3WN







-----Ursprüngliche Nachricht-----
Von: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] Im
Auftrag von Tom Azlin N4ZPT
Gesendet: Freitag, 9. April 2010 00:28
An: AMSAT-BB
Betreff: [amsat-bb] Re: BeeSat at 4800 GMSK

Hi Nate,

I was not aware MixW had MSK in it but still identical to GMSK. Perhaps 
you are thinking of MFSK? In the MixW program there is MSFK16, a 
multitone frequency shift signal, is supported, but not Minimum Shift 
Keying or Gaussian Minimum Shift Keying signals. And also FSK, aka RTTY.

There is work going on to make a sound card 4800 bps 0.5 time-bandwidth 
product GMSK soundcard modems for use in GMSK DV adapters to use with 
D-STAR radios. Perhaps that could be adapted for your purpose?

http://www.qsl.net/kb9mwr/projects/voip/dstar/G4KLX.html seems to 
describe some of the work.

http://groups.yahoo.com/group/dstar_development/ and 
ttp://groups.yahoo.com/group/pcrepeatercontroller/ are where I see the 
discussion underway.

Separate discussion is using an external sound card interface like the 
Rigblaster, to connect a computer and radio.

73, Tom n4zpt

Nathaniel S. Parsons wrote:
> Can I assume MSK=GMSK? I thought they were different, but they are the
same,
> and since MixW has MSK, and I could use that with a Rigblaster, etc,
right?
> 
> -Nate
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