Observation 2825147: UPMSat 2 (99799)

Regarding Observation 2825147

I can’t have good audio from UPMSat2. I don’t know whats the reason.

Seems that is not centered enough…

The BPSK demodulator audio output places the signal of interest at ~12 kHz (tones at ~11800 and 13000 Hz) in the audio passband. This is true whatever the baud rate is set to, and was decided on because it’s what gr-satellites uses as an IF for its BPSK demodulator, and the other ‘target’ decoder (the Funcube Dashboards) will pick up the frequency automatically.

My guess is whatever decoder you are using is looking for the FSK tones over a fairly constrained frequency range, most likely only up to a few kHz. For example the UZ7HO soundmodem application only works with a sample rate of 8kHz - 12 kHz, limiting the maximum frequency it can observe to about 4-6 kHz.

I tried to get direwolf to use the actual tones, but it decided they were unreasonable and went back to the defaults.