Decoding frames from the Monitor-2 satellite

[Foxiks]

Hello!
I tried to demodulate a dump with data from the Monitor-2 satellite at a frequency of 435.815 MHz. And it seems to have worked out for me.

I made a simple flowgraph that decodes a signal into a raw bitstream.

After receiving the bits of information, I used a deframer with the sync word 0xb1d2769bacf51f2087 and this allowed me to get transport packets with a length of 1136 bits.

Could you add support for this satellite to gr-satellites?

[daniestevez]

Hi @Foxiks, can you give more details or link to documentation about this satellite? I would need information about scrambling, FEC, CRC, etc. Do some of the other Russian satellites use the same modulation and coding (see #530, #531, #532)?

[Foxiks]

Unfortunately I do not have documentation for this type of signal.

[janvgils]

The FM/PM part seems to be Doka, so apart from AFSK AX.25 the satellite is also dumping data using the Doka scheme.

If you follow this link, you can find some information that I found in the past.

[janvgils]

An example observation with both AFSK and FSK https://network.satnogs.org/observations/8874840/

[K4KDR]

The FSK at the beginning of that SatNogs observation appears to be 9600-something... if you just use the 'FSK Demodulator' block and stream the resulting bytes into a .bin file, there are a lot of patterns that repeat throughout.

... this was obtained using:

... but I could not get a match from any of the deframers at my disposal.

-Scott