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Description:
This unlike domestic television is a
method of transmitting frozen pictures over a very narrow
bandwidth, on frequencies normally used for speech by Radio Amateurs.
SSTV was originally invented by Copthorne Macdonald
and first used by Radio Amateurs, but is
now used by large groups of professionals such as Police &
Security services. The original idea was to find a method
of transmitting a television picture over a single speech
channel. This meant that a typical (at that time) 3MHz wide
television picture had to be reduced to around 3kHz (1000:1
reduction). It was decided at the
outset that the scanning rates must be very
slow, which precludes the use of moving pictures.
The choice of time base for synchronising was the readily
available domestic power supply at 50
or 60 Hz (depending on the country of origin).
This gave a line speed of 16.6Hz and 120 or 128
lines per frame (against the then UK standard
of 405 lines (now 625) per frame), giving a new picture frame
every 7.2 or 8 seconds.
The maximum bandwidth is 3kHz, therefore
the SSTV signals bandwidth is restricted
to 2.3kHz, Black is represented by a 1500Hz
tone and white by a 2300 Hz tone together with a sync pulse
at 1200Hz well below the black level so it would be invisible. The
Sync pulses are sent at the end of each
line are 5ms in length and at the end of each frame 30ms.
| SSTV
frequencies are:
- 1'838.15 MHz
- 3'580.15 MHz
- 10'140.15 MHz
- 14'070 MHz
- 21'340 MHz
- 28'320 MHz
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Other
HAMSoft
- ProSkan
- WinSkan
- SSTV 32
- Chroma Pix
- Chroma Sound
- JVComm32
- SSTVBL 1.5
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working conditions:
- Icom IC-746
- Intel Pentium MMX 200
- SB - Yamaha 64
- MM-SSTV
Chroma Pix
- interface
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It
also works with:
- 486/33 CPU
- SB 16 bit
- interface
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The screenshot:
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| The MMSSTV 1.2 |
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SSTVSB)
Pic.01
[for Icom] 
SSTV
SB interface Pic.02
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