SSTV

Slow Scan Television

SSTV is a narrowband method of sending static images by radio similar to radiofax systems but with the advantage of being capable of colour transmission. Mainly the province of Radio Amateurs the method has an illustrious background within NASA and other space agencies being employed on Luna 3 to send images from the far side of the moon, Vostok, Apollo 8, 9, 10 and the Apollo 11 Lunar Lander.

The early implementations were relatively low resolution but had relatively short transmission times, more modern implementations which use computers and sound cards in place of the original complex arrangement of a scanner or camera, a modem to create and receive the characteristic audio howl, and a long-persistence cathode-ray tube that keep a picture visible for about ten seconds have increased the resolution and transmit times.

SSTV is still in use on HF sections of the Amateur Radio spectrum and it is periodically employed on the International Space Station (ISS) specifically utilising the on-board Amateur Radio equipment.

Modes, Resolution and Transmission Times

Family Name Color Time Lines/Resolution
AVT 8 BW or 1 of R, G or B 8s 128×128
16w BW or 1 of R, G or B 16s 256×128
16h BW or 1 of R, G or B 16s 128×256
32 BW or 1 of R, G or B 32s 256×256
24 RGB 24s 128×128
48w RGB 48s 256×128
48h RGB 48s 128×256
104 RGB 96s 256×256
Martin M1 RGB 114s 240 (+16 greyscale lines)
M2 RGB 58s 240 (+16 greyscale lines)
Robot 8 BW or 1 of R, G or B 8s 120
12 YUV 12s 128 luma, 32/32 chroma x 120
24 YUV 24s 128 luma, 64/64 chroma x 120
32 BW or 1 of R, G or B 32s 256×240
36 YUV 36s 256 luma, 64/64 chroma x 120
72 YUV 72s 256 luma, 128/128 chroma x 120
Scottie S1 RGB 110s 240 (+16 greyscale lines)
S2 RGB 71s 240 (+16 greyscale lines)
PD PD90 G, R-Y, B-Y 89.989120s 320×256
PD120 126.103040s 640×496
PD160 160.883200s 512×400
PD180 187.051520s 640×496
PD240 248.000000s 640×496

How do I Send or Receive SSTV

Although SSTV is an analogue mode the configuration to operate this mode is essentially the same as you would use for digital modes such as PSK31, PSK64, FT8 etc. Essentially you will need:

  • An antenna, ideally resonant at the frequency of operation
  • An ATU if the antenna isn’t sufficiently resonant at the frequency of operation
  • A transceiver capable of transmitting and receiving with the desired mode on the frequency of choice
  • An audio interface capable of taking the audio from/to the transceiver to/from a computer, tablet or phone
  • If you intend to send SSTV as well as receive it then you will need some method of commanding the transceiver to go to transmit when you are ready to send. This might be provided by your audio interface, a digital vox function within your transceiver or a separate CAT control line
  • SSTV software such as QSSTV compatible with your device and operating system

This isn’t meant to be a tutorial on how to set your specific system up but the above list will at least ensure that you have all of the necessary equipment.

For an indication of where to find SSTV activity within the Amateur Radio spectrum you should consult the band plans. In the UK the RSGB is a good resource.

Examples of ISS SSTV Images

The list below links to some images received with a simple ground station during periods of SSTV activity from the ISS:

Some of these are more successful than others. This is for a variety of reasons including: testing new equipment and timing of the passes.