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Analog Slow Scan TV

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Analog Slow Scan TV Empty Analog Slow Scan TV

Post by AJ2X on Mon Sep 14, 2020 7:54 pm

I'm researching for an article about early SSTV (Slow Scan Television). My initial idea was about Copthorne MacDonald's 120-line, 8-second scan system for Ham Radio, and I'd really like to know more about what equipment people built and used with that system. However, there may be more, including radio facsimile systems, satellite and astronaut video, and even 1920s-era mechanical TV, that would fit the description too.

Does anyone have experience and/or knowledge of slow scan TV, prior to the 1970s and the beginning of digital storage and scan conversion?

Thanks!

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Post by Chas on Mon Sep 14, 2020 8:16 pm

I converted a DeskFax for AFSK on 6 meters 50 YA. I still have the gear, stored. I used some QST conversion and added my own conversion to create a sync. I never got involved in any other Ham media except RTTY. Cost was the factor as well as "How many other folks have the equipment to exchange communication with?"
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Post by AJ2X on Mon Sep 14, 2020 9:00 pm

Thanks, Chas. I remember helping a Ham co-worker with the conversion of a DeskFax to receive weather satellite pictures in 1971. At the time I didn't know there was a way to use them on the Ham bands. There probably weren't that many DeskFax conversions for Ham use, so I can completely get losing interest after a while - an awful lot of unanswered "CQ Fax" calls would be discouraging.

But now I'm going to have to look up QST articles about that, since it might shed some light on SSTV.

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Post by Chas on Mon Sep 14, 2020 9:05 pm

"CQ Fax" calls would be discouraging.
Hi, Hi, hi...

Key your call in narrow shift and start scanning the document with your call written on the paper. Could it be that simple.. Very Happy ..

Go to 'fridge, get beer, open beer. Sit down and run it again... Go to cabinet and get beer nuts, sit down run it again.  Keep fresh fax paper ready for reply. Then change the frequency and do it agin... When beer is gone go back to AM and chat with the locals while they moan about the tweedle, tweedle, tweedle Ha!

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Post by AJ2X on Mon Sep 14, 2020 9:22 pm

Sounds about right!

I did a quick search and found the 1972 QST article on conversion. It didn't have any info on what the scan time and line count was for those units. Do you know what it was? I seem to remember that the weather sat conversion took quite a while to print an image.

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