SSTV(Slow Scan TV)

Slow-scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or color.
A technical term for SSTV is narrow band television. Usual broadcast television requires huge 5, 6 or 8 MHz wide channels, because it transmits 25 or 30 pictures per second (in the NTSC, PAL or SECAM systems), but SSTV via Radio usually takes up to only 3 kHz of bandwidth. It is a much slower method of still picture transmission, usually lasting from about eight seconds to a couple of minutes.
Since SSTV systems operate on voice frequencies, amateurs use it on shortwave (also known as HF by amateur radio operators), VHF and UHF radio.

In HF range usually SSTV can be heard at these frequencies

Band Frequency Sideband
80 meters 3845 kHz (3730 in Europe) LSB
40 meters 7170 kHz (7043 in Europe) LSB
20 meters 14230 kHz USB
15 meters 21340 kHz USB
10 meters 28680 kHz USB
6 meters 50.680 MHz FM
2 meters 145.5 MHz FM

Things that you need for SSTV operation.

Software:
Recommended freeware MMSSTV from JE3HHT. A very popular SSTV software.

Hardware:
You need to have a pc to run SSTV program
An interface between your pc and your transceiver
Last but not least is the transceiver

Today's SSTV programs can be run in either dos or window base environment. Even Linux. All available for download from Internet.

As for interface, lots of varieties of interface configuration that you can use to run your SSTV. Either homebrew or commercially buy one. One of the commercially available is from Westmountainradio's rigblaster.

If you are a shortwave listener(SWL), there is no need for you to have the interface because you won't be making any transmission. But SWL is encouraged to monitor SSTV with the varieties of SSTV software available to see how others hams use SSTV mode.

Example of SSTV Reception picture:

SSTV works by horizontally scanning the pictures start from the top till the bottom and left to right. Which converts to frequency using analogue frequency modulation direct proportional to the picture's brightness. Brightness control which fall between 1.5KHz to 2.3KHz. The higher the brightness of the area scanned, the nearer the peak to 2.3KHz and this applied also to low brightness near to 1.5KHz. Besides that, the system also send series of 1.2KHz clicks for synchronization.

Here is the example scanning signal:

The usual information's that sends along with the picture is the Callsign of station being called, RST and Caller's Callsign. One thing to remember is, SSTV works totally depends on band condition over HF. This mean QRM, QRN, QSB and some other effects may makes SSTV reception difficult or poor. But in 2m or 70cm works fine. There are many format that Radio Amateur's use which is:

ROBOT 36, ROBOT 72, AVT 90, SCOTTIE 1, SCOTTIE 2, SCOTTIE DX, MARTIN 1, MARTIN 2, B/W 8 and the quality of the pictures directly proportional to the picture's pixel depth.

More coming up for other mode.