📡 orbcomm-rx - STX Demodulator and Decoder

orbcomm-rx is a demodulator and decoder for the Orbcomm VHF Subscriber Transmitter (STX) downlink. Each satellite in the Orbcomm constellation transmits two STX carriers between 137-138 MHz. These downlinks contain satellite position data, orbital elements, uplink/downlink channel info, and encrypted user messages.

Demodulator

The STX downlinks are modulated using Symmetrical Differential Phase Shift Keying (SDPSK) at a data rate of 4.8 kbps.

Decoder

Resources

• “Ever wondered what is on the Orbcomm Satellite Downlink?” - Mike Kenny
• "The Orbcomm Experience" - Jochen Harms