SSTV stands for Slow Scan TeleVision. It is a mode used by amateur radio operators to send images, both color and black and white. An SSTV image takes from 8 seconds to several minutes to receive, depending on the mode used. In North America, Scottie S1 is the most commonly used mode. In Europe, Martin M1 is the most commonly used mode.
 
This button will clear the SSTV display, and reset the mode. MultiMode will now wait for the start signal and VIS code of the next SSTV image.
 
These two buttons are used to shift the image to the left and right. This is useful when reception was manually started.
 
The + and - buttons are used to adjust for timing differences between your Mac and the computer sending the SSTV image. Small offsets in timing can cause large skewing of the image. If the vertical edges of the image are diagonal, then these buttons should be used to correct the timing. The timing variation is shown to the right of the three buttons. 1.00000 means the timing is at the default value.
Clicking the + or - button will change the timing by 0.00001. Holding down the control key while clicking will cause the timing to change by 0.00010. Holding down the option key will cause the timing to change by 0.00100. The 0 button will reset the timing to the default value. You can change the timing while receiving an image, and the display will be automatically updated in real-time.
 
To the right of the timing buttons, the current SSTV mode is displayed. Clicking on the mode will display a popup menu, from which a new mode will be selected. MultiMode will automatically select the mode based on the VIS code sent. However, it is possble for the VIS code to get garbled, or you may manually start reception. Under these conditions, you need to select the correct SSTV mode. You may do so even while receiving an image, the old data ia preserved, and the image display will be automatically adjusted and updated.
 
The Start button allows you to manually start receiving an SSTV image. This is useful if the start signal and/or VIS code are not correctly received. It is also useful if you tune into a transmission that is already in progress.
The Stop button will stop reception of an image. Normally this occurs after the receive buffer fills up, after about four minutes.
SSTV Transmission
As of this release, only some of the modes properly transmit, notably Martin M1 and Scottie S1, the two most common modes. Eventually transmission will be supported in all of the modes. There may be some slight timing offsets in some of the modes, please bear with them for now.
To transmit an SSTV image, perform the following steps:
1. Select SSTV Mode.
2. Select the SSTV mode you wish to use.
3. Select Build SSTV File from the Control menu
4. A file open dialog will appear. Select the picture file. Note: at present, it must be a
PICT file. The should be the same size as the transmission mode uses, or some
distortion may occur. This will be fixed.
5. After the sound output file is built (when the watch cursor reverts to a normal
cursor) you may select Transmit mode from the Control menu, and the picture
will be sent.
At present, a 16 line grayscale title is included in all modes. You will be able to enter your callsign into this title in a future release of MultiMode.
SSTV Modes
MultiMode supports the following SSTV modes. Is your favorite mode not listed? Email me with the specifications for the mode, and I'll add support for it!
Robot Modes
8 Second B&W
12 Second B&W
24 Second B&W
36 Second B&W
36 Second Color (under development)
72 Second Color (under development)
Martin Modes
Martin M1
Martin M2
Martin M3
Martin M4
Scottie Modes
Scottie S1
Scottie S2
Scottie S3
Scottie S4
Scottie DX
SSTV Frequencies
The following SSTV frequencies are commonly used. 14230 MHz is by far the most popular frequency. SSTV nets may be heard throughout the weekend.
