To demodulate 1KUNS-PF, we suggest using either the tool from radio amateur UZ7HO, SoundModem http://uz7.ho.ua/packetradio.htm. In the “other-versions.zip” file you can find the demodulator specific to our CubeSat. Special thanks to UZ7HO for providing such a great tool.
Another option is using the splendid gr-satellites repository with GNURadio https://github.com/daniestevez/gr-satellites, in which you will find both the telemetry and the image decoder.
As of the antenna to use, when running in 9k6 baud it is difficult to demodulate the signal with an omnidirectional antenna unless the passage is quite high. The recommendation is a Yagi even roughly pointed towards the CubeSat.
You will find that we transmit a lot of packets over Europe and Kenya, so if you are around you will receive much more than the beacon!
The signal properties are as follows:
- Frequency: 437.300 MHz
- Modulation: GMSK
- Baud rate: 9600 bps, fallback to 1200 bps
- Beacon frequency: 1/15 s
- Telemetry frequency: on request
- Polarization: any (can be RHCP, LHCP, vertical or horizontal depending on how 1KUNS-PF is oriented!)
More info on the satellite on https://db.satnogs.org/satellite/43466/ as well.
Images: The images are JPEG encoded. They have a two-byte preamble that indicates what number packet is being transmitted, after which 128 bytes of JPEG encoded data follow. We usually do not transmit the first 4 packets (0 to 3) because they always contain the same bytes, in order to save time:
FF D8 FF E0 00 10 4A 46 49 46 00 01 01 01 00 00 00 00 00 00 FF DB 00 43 00 0C 08 09 0B 09 08 0C 0B 0A 0B 0E 0D 0C 0E 12 1E 14 12 11 11 12 25 1A 1C 16 1E 2C 26 2E 2D 2B 26 2A 29 30 36 45 3B 30 33 41 34 29 2A 3C 52 3D 41 47 4A 4D 4E 4D 2F 3A 55 5B 54 4B 5A 45 4C 4D 4A FF DB 00 43 01 0D 0E 0E 12 10 12 23 14 14 23 4A 32 2A 32 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A 4A FF C4 00 1F 00 00 01 05 01 01 01 01 01 01 00 00 00 00 00 00 00 00 01 02 03 04 05 06 07 08 09 0A 0B FF C4 00 B5 10 00 02 01 03 03 02 04 03 05 05 04 04 00 00 01 7D 01 02 03 00 04 11 05 12 21 31 41 06 13 51 61 07 22 71 14 32 81 91 A1 08 23 42 B1 C1 15 52 D1 F0 24 33 62 72 82 09 0A 16 17 18 19 1A 25 26 27 28 29 2A 34 35 36 37 38 39 3A 43 44 45 46 47 48 49 4A 53 54 55 56 57 58 59 5A 63 64 65 66 67 68 69 6A 73 74 75 76 77 78 79 7A 83 84 85 86 87 88 89 8A 92 93 94 95 96 97 98 99 9A A2 A3 A4 A5 A6 A7 A8 A9 AA B2 B3 B4 B5 B6 B7 B8 B9 BA C2 C3 C4 C5 C6 C7 C8 C9 CA D2 D3 D4 D5 D6 D7 D8 D9 DA E1 E2 E3 E4 E5 E6 E7 E8 E9 EA F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FF C4 00 1F 01 00 03 01 01 01 01 01 01 01 01 01 00 00 00 00 00 00 01 02 03 04 05 06 07 08 09 0A 0B FF C4 00 B5 11 00 02 01 02 04 04 03 04 07 05 04 04 00 01 02 77 00 01 02 03 11 04 05 21 31 06 12 41 51 07 61 71 13 22 32 81 08 14 42 91 A1 B1 C1 09 23 33 52 F0 15 62 72 D1 0A 16 24 34 E1 25 F1 17 18 19 1A 26 27 28 29 2A 35 36 37 38 39 3A 43 44 45 46 47 48 49 4A 53 54 55 56 57 58 59 5A 63 64 65 66 67 68 69 6A 73 74 75