KG-STV - A DIGITAL SSTV SYSTEM BY JJ0OBZ
KG-STV is a digital SSTV
system developed by JJ0OBZ. Images are split into blocks of
16x16 pixels which are compressed then transmitted. All
images are 320x240 just like some analogue SSTV modes.
KG-STV only uses 600Hz bandwidth and errors in the received image, due
to fading, QRM, etc., can be corrected by sending a Bad
Segment Report (BSR) back to the originating station which can
retransmit the required blocks to complete the image. Short
text-based messages can also be sent.
Above you can see the KG-STV
window. On inital start up click on "Settings" to set up your
sound card, callsign, waterfall colour etc. Most of the
options on the right-hand side of the Settings window can be left
alone. "Image Block Scan Direction" determines how the 16x16
blocks are transmitted, horizontally (similar to SSTV), vertically, or
randomly. KG-STV is clever enough to know which block goes
where so this setting does
not have to match the setting at the receiving station.
Once all options are configured correctly click OK to return
to the main window.
Drag and drop an image into to
right-hand box or click "From Clipboard" to paste an image from
clipboard. In the screenshot above I pasted a picture of a
bird. The image will be compressed and the time it will take
for the picture to be transmitted will be displayed below the image
- 2 minutes, 24 seconds in the example above.
Clicking on the "Mode" drop-down
menu allows you to choose between "MSK" and "4L-MSK". Four
level MSK is faster than MSK but more errors may occur. The
"Code" drop-down menu lets you choose from "Normal" or "Convolution"
encoding, the latter being more robust so is less prone to errors, but
is also slower than the "Normal" setting. Finally the "Scale"
drop-down menu lets you determine how much JPEG compression is applied
to your image. Too much compression can reduce the image
quality and too little may result in an excessively long transmit time.
As you adjust the settings in these menus you will notice
that the "TxTime" figure alters accordingly. "MSK - Mode" and
"Normal - Coding" are probably the best settings for use on the 20m
band. Whatever settings you choose for transmission of an
image will be detected automatically be the receiving station.
you are ready to transmit your image click on "Send Image" and
transmission will commence.