SSTV is used to transmit still images over a voice channel. Using a SSB transceiver images may be transmitted world-wide. SSTV is a television standard as the images are scanned row by row and then transmitted at a very low rate hence the designation Slow Scan Television. SSTV is normally used by radio amateurs.

SSTV transmissions come in a variety of modes. The picture resolution varies from 120 x 120 and a transmission time of 8 seconds to 640 x 480 with a transmission time of over seven minutes. Some transmissions are black-and-white only, and others are in color using either R-G-B or Y-U-V color coding.

On the air, the most common modes are the Scottie and Martin modes.

The WAVECOM SSTV decoder can decode a variety of modes: Martin 1-4, Scottie 1-4, SC-1 modes, SC-2 modes and B/W Robot modes. These modes can be detected automatically. Modes that use Y-U-V color coding are not supported.

Use the Auto button to select automatic mode or alternatively select a specific SSTV Mode in the Options menu. If a specific mode is selected, the system will not change mode if a SSTV signal of a different mode is detected.

If Free Run in the Options menu is selected, an image line will be displayed even if no valid Horizontal Sync (i.e., start of a new line) is detected. When Free Run is selected, the decoder does not adjust the picture timings to match the received signal. To manually correct the horizontal timing one uses the Alignment option. When the alignment is correct, the picture will be received vertically. One would normally only use Free Run mode if the signal is very noisy and the system cannot detect the sync pulses itself or if the picture is very wavy.

Click and drag on the image with the left mouse button to select a portion of the image. The selected portion is displayed in reverse colors. Right-clicking on the picture will bring up a popup menu. To copy the highlighted portion of the image, use the Copy item in the popup menu. This copy can be pasted into any graphics application (e.g., WINDOWS Paint), and then stored as an image file using the application.

The popup menu also includes zoom options. Different zoom settings from 10% to 400% are available.

For the proper functioning of SSTV, the receiver must be correctly tuned. To assist in tuning, the SSTV display includes a frequency spectrum in the lower window. When correctly tuned, one should see a frequency spike around the sync frequency, and a wide band of frequencies between the black and white frequencies. To visually aid tuning, markers are displayed at the Sync, Black and White frequencies.

SSTV Standards for Synchronization

SSTV Modes

Notes:

*          Not implemented

a          Top 16 lines gray scale

b          Top 8 lines gray scale

c          Similar to original SSTV

d          No horizontal sync (start of a new line)