D-STAR One Mobitex protocol decoded

D-STAR One are a series of Amateur satellites with an on-board D-STAR digital voice repeater. The first satellite of the series, called D-STAR One, was launched on November 2017 but was lost due to a problem with the upper stage of the rocket. The second satellite, called D-STAR One v1.1 Phoenix, was launched in February 2018 but never worked. On 27 December 2018, a Soyuz rocket launched the next two satellites in the series: D-STAR One Sparrow and D-STAR One iSat. I hear that, unfortunately, these two newer satellites haven’t been coordinated by IARU.

Besides using the D-STAR protocol, these two satellites also transmit telemetry in the 70cm Amateur satellite band using the Mobitex protocol, as described in the CMX990 modem datasheet. They use GFSK at 4800 baud.

In the past, I have talked about the Mobitex protocol in the context of the BEESAT satellites by TU Berlin. I described some notes about the Mobitex-NX variant used in these satellites, and contributed to the beesat-sdr GNU Radio decoder for the Mobitex-NX protocol.

Now, I have adapted the Mobitex-NX decoder to work also with the D-STAR One satellites, and added a decoder to gr-satellites. The decoder requires my fork of beesat-sdr to be installed.

Continue reading “D-STAR One Mobitex protocol decoded”