Information for radio amateurs

This page is dedicated to the amateur radio community and lists information related to our active satellite missions. 

Want to get involved? Find information [1] on what we offer at TU Berlin, including a list of our operators and hams who we helped to obtain their license.

All missions use half-duplex communications. Therefore, the above listed frequencies are valid for Up- and Downlink.

A GNU Radio out of tree (OOT) module is published on GitHub [2] which can be used to demodulate raw data frames from our satellites. It demodulates the bit stream modulated with GMSK and also the Mobitex data-link layer protocol. Additionally, the Soundmodem [3] from UZ7HO supports demodulation of Mobitex frames. 

To launch the GNU Radio modules, use the flowcharts provided in the grc subfolder of the GitHub [4] repository. For BEESAT-1 use tnc_b1.grc and tnc_nx.grc for BEESAT-2,-3,-4 and -9. The flowcharts provide a TCP sever connection on port 9000 which is used to transmit demodulated messages to other programs.
The format of the messages is described in the files below.

The standard baudrate is 4800 bps but can be switched to 9600 bps for increased channel capacity at higher elevations. Each transmission at the higher baudrate is announced by a small 4800 bps header to allow for adaptive receiver re-configuration. The output power of the satellites is 27 dBm (0.5 W) for all BEESATs and 30 dBm (1 W) for TechnoSat using quarter-wave monopole antennas with toroidal radiation pattern.

On the data-link layer - as described by the OSI model - all BEESATs and TechnoSat make use of the Mobitex protocol. The modem chip used on BEESAT-1 to -4 is CML CMX909b [5]. It includes scrambling and interleaving features and forward error correction is also performed internally.

The transport layer uses individual frame headers for addressing multiple satellites and for handling variable length messages. Additionally, backward error correction adds to data consistency and transmission safety when needed. Both protocol features are realized by the attached microcontroller of the on-board and groundstation TNC.

TUBIN will be launched in 2020 and use the same telemetry format as TechnoSat. Any changes in the format will be announced prior to launch, however the modulation and coding will not change and the same TNC/ gr-tools can be used as for BEESAT and TechnoSat.

Telecommand uplink and telemetry downlink always passes the terminal node controllers which are responsible for failure tolerant communication between the on-board computer and the groundstation's telemetry and telecommand server.

You may find a schematics of the TNC in the download section of this page for reference.

The telemetry format description of TUBiX10 protocol, currently implemented in mission S-NET [7]and SALSAT [8], can be download under "Files for Download [9]". 

The Chair of Space Technology operates a telemetry collector server to receive raw data frames via the Simple Downlink Share Convention (SiDS) [10]. Frames can be submitted through the URL http://fachgebiet.rft.tu-berlin.de/ham/telemetry/send [11]

GNU Radio Modules: github.com/kappiman/beesat-sdr [12]
Also included in gr-satellites [13] repository by EA4GPZ

Telemetry Collector Server: fachgebiet.rft.tu-berlin.de/ham/telemetry/send [14]

Telemetry Decoders by DK3WN: www.dk3wn.info/p/?page_id=75524 [15]