Cleveland RAYNET Group
SSTV and FAX (facsimile) are similar things. Over thirty years before Morse Code and telephones were used, a Scots scientist called Alexander Bain invented the fax machine. Using wires to connect two electro-mechanical machines together in 1843, documents such as pictures were first transferred from one machine to another for the first time.
Slow Scan TV uses speech (i.e. narrow) bandwidths to send still pictures or photographs. Each picture takes a long time to transfer. The quality of the received photograph depends on the transmission time. 58 seconds sends a viewable but not good quality picture. 71 seconds gives a reasonable quality picture. 114 seconds gives quite good quality and 269 seconds gives extremely good quality.
The SSTV pictures could be a series of unconnected pictures e.g. my cat, my dog, my room, me. They could also be a series of pictures showing the development of an event e.g. a marathon race.
The disadvantage is the length of time to send a picture. The advantage is that they are sent on normal speech transmitters and so can be sent locally or across the world without requiring specialised equipment.
The hardware required is an amateur band transceiver, a PC and a couple of cables to connect them. If the pictures to be sent don't already exist on the PC, a digital camera is required.
Weak radio signals will insert random noise (dots) into the received pictures. Much of this video noise can be removed with the click of a button using SSTV software.
Sample SSTV Picture
This SSTV picture was sent twice without any noise filtering or other improvements. It was sent once with a very weak signal. It was then sent back with the same weak signal path.
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Page updated on 09 January 2017