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SatMe PC SSDV
← SatMe-PC guide · October 2026
SSDV is a picture cut into 256-byte packets (JPEG blocks, CRC-32 and Reed-Solomon): each packet received puts its blocks in place, the missing ones stay grey, and a picture sent again later fills the gaps. SatMe-PC decodes it from several kinds of signal, gathers the packets pass after pass, and shows the pictures in Télémesure › Images SSDV and in the SSTV tab. Receive only: nothing is ever transmitted.
The chain follows the satellite's transmitter in SatNOGS DB:
| Satellite | Signal | Where SatMe-PC reads it |
|---|---|---|
| SO-127 (HADES-SA) and AMSAT-EA's other « GENESIS » satellites | narrow two-tone FSK, heard in USB | Télémesure › SSDV en BLU (below) |
| IO-86 (LAPAN-A2) | SSDV relayed by its FM repeater in AFSK 1200 (ssdv2sat) | the sound card's APRS decoder (rig in FM): bare or AX.25 frames, whole or shorter packets; the pass labelled « AFSK 1200 » |
| cubesats in FSK / GMSK 1200–9600 bit/s | packets | Télémesure › Paquets (the SDR's I/Q, see Telemetry) |
| Geoscan-2/4/5, 239Alferov | no SSDV but JPEG chunks in their GFSK 9600 frames (sync word 0x930B51DE, PN9 whitening, CRC-16) | the same packet decoder; the picture shows as the chunks come (kept in telemesure/geoscan/) |
Not read yet: ASRTU-1 (BPSK 9600, CCSDS concatenated coding). Every decoder is off by default.
In Suivi › Fréquences (Doppler), the transmitters' list now shows every live transmitter of the satellite (SatNOGS DB), whatever its mode (« SSDV », « GENESIS FSK »…), each with its frequency and the mode the rig takes. Slow FSK (under 1200 bit/s), SSDV and SO-127's « GENESIS FSK » put the IC-9700 in USB-D (USB in data mode: the audio from the rear, the microphone muted) — no longer FM.
Autre fréquence… (another frequency), at the bottom of the list: a downlink in MHz, an optional uplink (SatMe never transmits by itself) and the rig's mode (USB, USB-D, LSB, LSB-D, FM, FM-D, CW); Doppler-corrected like the others and kept for that satellite; Oublier (forget) removes it. The page served to the phone does the same. See Suivi.
SO-127 (HADES-SA, 436.875 MHz) sends 2-FSK directly on the carrier: 800 bit/s with 1600 Hz between the two tones (200 bit/s with 1125 Hz some months). An FM receiver loses it; in USB it is two audio tones.
Where: workspace Modes › Télémesure › SSDV en BLU.
- The rig: follow the satellite, then pick its transmitter « SSDV », « GENESIS FSK » or « FSK 800 » in Fréquences (Doppler): SatMe sets the IC-9700 to USB-D on the downlink, Doppler corrected.
- The sound: carte son (the Son tab's card — the IC-9700's USB codec) or récepteur SDR (the SDR in USB).
- Débit (rate): from the transmitter, or 800 / 200 bit/s by hand.
- Tick the decoder. The two tones are searched across the audio band (the Doppler's residue followed), then the GENESIS frames (sync 0xBF35, CRC-16, descrambler) and an SSDV search straight in the bits: a packet comes out even if the framing were misread.
-
Capturer les bits (capture the bits): each pass's demodulated bits kept (
telemesure/genesis/), to read again or study later. - Relire (read again): a recording of the Son tab, a capture, or Fichier… — a WAV of USB audio from any program (8 to 32-bit PCM or float, mono or stereo). Its packets join the pictures, the pass named after the file.
- Essai (test): a made-up test chart in SSDV packets, with noise and drift, through a decoder of its own; nothing kept.
Checked on made-up signals only (noise, drift, both rates). To check it on a real pass: record the pass's USB audio (Son › Enregistrer, the rig in USB-D on SO-127's « SSDV » transmitter) with Capturer les bits ticked, then Relire the recording.
The Images SSDV sub-tab rebuilds the pictures found in every decoder's packets, packet by packet; the picture updates live during the pass.
- Over several passes: satellites often send a picture again, or its rest, an orbit or a day later. A packet with the same callsign and image number as a picture received within the last 3 days, of the same size and quality, completes it. Duplicates (both bit readings, a replay, an import) are kept once; every packet's CRC is checked.
- Each picture shows N/M paquets, X % (M guessed, « ≈ », until the last packet came), en cours (under way) or complète, a strip of its packets coloured by the pass that brought them (dark: missing), and the list of passes (time, packets, source).
-
Kept on disk (
telemesure/ssdv/paquets/): a picture under way survives a restart. A complete picture is written as a JPEG and joins the gallery. - ⤓ PNG / ⤓ JPEG export a picture as it stands (missing blocks grey); Abandonner (give up) forgets a picture under way and its packets.
- Importer des paquets… (import packets): the packets of a missed pass from a file — raw SSDV packets, a KISS file, or SatMe's frame log. They join the pictures as a pass of their own.
- In the demonstration (
--demo), two made-up pictures put together over two passes: one complete, one still a few packets short.
SSTV › Images also shows the SSDV pictures of the last three days, under way or complete, with their packets received and missing and the passes that brought them: the satellite pictures in one place. See SSTV.
An Agenda › SSTV · auto-pilote campaign can receive SSDV: Décodeur SSDV en BLU (SO-127) in its receiving chain (ticked by itself for a satellite that sends this way) switches the decoder on for its passes, from the campaign's sound, then puts things back as they were. The campaign's own frequency may be USB or USB-D. The pass's report says how many packets came. Receive only: the satellite's uplink is never used. See SSTV campaigns: the auto-pilot.
With web publishing ready, the 🌐 under each picture sends it to your site (type ssdv-image, Sur clic by default, or Automatique): satellite, NORAD number, first and last packet, packets received / expected and missing, the passes that brought some (and the auto-pilot). A picture already sent goes again by itself when more packets come, under the same key: the site replaces it. To a folder too.