Getting started with slow scan television Glidden R.L.
Glidden R.L.
Год: 1990
Количество страниц: 5
Язык: Английский
Формат: PDF / RAR
Формат файла: RAR
Think of all the methods hams use to communicate with Teach other. The short list would include speech, data and Morse code. Did you forget images? At 420 MHz and up, hams routinely exchange live, full-motion video. It's called fast-scan television (FSTV)—the same TV you're accustomed to seeing at home. FSTV is a fun mode, but the transmitted range is limited to a few hundred miles under the best conditions. In addition, special transmitters and receivers are required.
But what if you wanted to share images over thousands of miles? You could take a fixed (nonmoving) image and slowly scan it line by line, converting the color and brightness variations into audio tones. Feed the audio tones to an ordinary SSB voice transceiver and you can send this information almost anywhere in the world. On the receiving end, the audio tones are translated back into an image on a computer screen. Hams call this technique slow-scan television (SSTV). Although it has neither the movement or the high resolution of FSTV, the advantage of SSTV is that you can send pictures over great distances without relaying devices or special transmitting gear by using the propagation characteristic of the high-frequency bands.
Thanks to the proliferation of personal computers and sound cards, it has never been easier to enter the world of SSTV. Most SSTV activity takes place on 20 meters, but you'll find it on other bands as well. Hams licensed as Technicians should note that SSTV can be used on VHF, too. You'll find activity on 6 meters from time to time, and a few amateurs have even swapped SSTV images via satellite!
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