Slow Scan Television (SSTV) is a ham radio operating mode in which pictures are transmitted over radio, via tones of 1500-2300 Hz with synchronization pulses at 1200 Hz. I.e., it uses the same bandwidth as voice communications, rather than video bandwidth (several MHz). This bandwidth limitation implies that the scan rate is much lower than full-motion video: a single still image in roughly one minute, rather than some 30 frames per second. The 3 kHz bandwidth can be accommodated by standard SSB and FM transceivers (and phone lines).

In the original SSTV days (late 1950s, early 1960s), special SSTV monitors used surplus P7-phospor radar picture tubes with roughly 8 sec after-glow retention of the image. In those days, transmission of each (monochrome) image frame of 120 lines took 8 sec, or 1/15 sec per scan line. Images were captured with a vidicon tube or a  modified video camera for "live" images, and fly-spot scanners for printed images. Extensive equipment was required. In the 1970s, digital circuitry and solid state cameras simplified the process. Today, standard image resolution is 320x240 (240 lines of 320 pixels) in 16-bit color, or even 640x480 in 24-bit color. As the audio bandwidth has not been increased, the image transmission time has increased to 1-2 minutes. Image transmission and reception is now simply done on PCs that interface with the transceiver via the soundcard and very simple & cheap interface circuitry. Excellent freeware is available. You can be on the air with SSTV in less then an hour. 

Over the years, several "families" of  transmission modes have emerged, each with different characteristics. Each family also has a  number of sub-modes, typ. differing in the number of scan lines (e.g., 120 or 240) and transmission time (longer translates to higher image quality potential). The modes Scottie 1, Scottie 2, Martin 1, and Martin 2 are the most popular (to some extent depending on the part of the world that the operator is in). Today's PC software supports transmission and reception of practically all sub-modes. Some examples are listed in the table below (B&W = black&white; RGB = Red-Green-Blue, YC = luminance/chrominance).

Audio spectrum of a typical SSTV image

A special form of SSTV is Narrow Band Television (NBTV). It uses 32 lines that are vertically scanned, an image aspect ratio of 2:3, and an audio spectrum of 2-10 kHz. It is a direct derivative of the TV system invented by J.L. Baird in the late 1920s.

The above SSTV modes are all analog modes, similar to fax. Digital SSTV is emerging. Images are transmitted as data blocks. It has some advantages (e.g., the possibility of including Forward Error Correction), but its current implementations may involve image pre- and post-processing, and require receipt of entire images. Here and here is more info on this mode.

None of the above is to be confused with Amateur TV (ATV). It is the equivalent of commercial TV with full-size, full-motion images and sound. ATV is practiced on frequencies of 430 MHz and up (i.e., the 70-cm, 23, 13, and 3-cm amateur bands). For operation in the 430-440 MHz band, a standard TV tuner with UHF channels 21 and below. Bandwidth of image + sound is about 7 MHz (for AM image + FM sound) or 20 MHz for FM-ATV (23-cm band and above). Transmissions require a video source (camera, recorder, PC, or test image generator), a microphone, and an ATV modulator/transmitter. With the advent of digital terrestrial commercial TV transmissions (DVB TV), ham radio operators are also adopting digital standards.

	Click here for some sample SSTV pictures of my QSO's etc.
	Live remote SSTV receivers: Click here for my SSTV WebCam with the last images that I received (updated every minute when my receiver is on) Other SSTV WebCams: click here (AE6JN) or here (N9UEW) or here (WD7F) or here for worldwide SSTV stations that show their own most recently received SSTV image(s) on the web, as well as those of other SSTV cam sites; I use them as remote receivers to check my transmissions, and propagation conditions.
	To hear what an SSTV signal sounds like, click here here (Mode "Martin 1") or here or here. (can be used to try out the software such as MMSTV - see below).
	Click here for "Getting Started with Slow Scan Television", by R.L. Glidden, WN5NOO, QST, September 1999, pp. 53-56, © 1999 ARRL.
	Lots of SSTV links here.

	Currently I am using excellent freeware SSTV-software (send/receive) for Windows®, developed by Makoto Mori, JE3HHT. MMSSTV supports all of today's most popular SSTV modes, has a built-in image editor for manipulating pictures, overlaying call-signs and other text, and uses the PC's sound card. Click on the button below to go to the MMSSTV page where the software can be downloaded. There are many other SSTV programs available, e.g., here.
	I use FTP Widget from John, KE5RS, to automatically upload received SSTV pix to my website
	I use QuickMix to save/restore my specific PC's soundcard settings for each of my ham radio programs.
	Click here for a description of how I hook up my PC to my radio; here, here, and here re some more audio (and CAT) interfaces.

Regular SSTV activity can be found on these amateur radio frequencies:    1843-2000 kHz    1890 kHz - calling freq    3590 kHz    3730-3740 kHz    3730 kHz - calling freq    3845 kHz    3857 kHz    7040-7045 kHz    7045 kHz - calling freq    7080-7100 kHz    7171 kHz    10130-10140 kHz    14070-14095 kHz    14255 - 14235 kHz    14230 kHz - calling freq    14233 kHz - calling freq    14240 kHz    14246 kHz    21070-21100 kHz    21335-21345 kHz    21340 kHz - calling freq    24975 kHz    28660-28700 kHz    28680 kHz - calling freq    50680 kHz    144.550 MHz    145.500 MHz

A list of regular frequencies with regular SSTV transmissions can be found here (160 meter through 70 cm band)

There is a Narrow Band TV (NBTV) net on Saturdays around 3.7 MHz from 08:00-08:30 UK time (this is UTC+1 during the summer)

Last update: July 2008
©2004-2008 F. Dörenberg N4SPP