6th September 2016

QB50 SE01 qbee nanosatellite

QB50 SE01 qbee nanosatellite

Find more information here.

Download the qbee beacon decoder here.

contact: qb01 (a.t} open-cosmos.com

Beacon Description


qbee‘s transmitter uses the following RF parameters:

Modulation GFSK
Modulation index 0.6667
Packet format AX-25*, CSP
Encoding NRZI with stuffing / G3RUH scrambled for AX.25, RS(223,255) for CSP
Carrier-Frequency 435.800 MHz
Nominal data rate 9600 baud
AX-25 Source Address Field ON01SE
Interval 10 s (LEOP), 30 s (during Operations [to be commanded])

*NOTE on AX.25: It is advised to turn off AX.25 decoding on the TNCs as the callsign fields from qbee are not formatted to the standard AX.25 and so the decoder will face issues. The AX.25 can be decoded by stripping off the heather (16bytes) and the footer (2bytes)

Byte and Bit order notes

Byte order: Least Significant Byte (LSB) first on multi-byte numbers

Bit order: Least Significant Bit first

Beacon Structure


Encoded NRZI
Scrambled G3RUH
CCSDS RS(223,255)
Preamble: 50x 0x7e AX.25 header AX.25 CRC16
50 bytes 16 bytes 2 bytes
CSP Header SAT ID Beacon data RS parity
4 bytes 4 bytes 28 bytes 32 bytes

Decoding procedure:

(fm_demodulate → demodulate_gfsk­ → clock_recovery →)  decode_g3ruh → decode_stuffed_nrzi → detect_preamble → extract_packets → deframe_ax25 → decode_rs → deframe_csp