NBTV: talk on optimising 32 line pictures.

[msf60khz]

Hi Chris

I saw your pictures in about 1975 at the first NBTV convention at Nottingham. They were displayed on a giant disc receiver with a neon and were very good.

Later on I made a 32 to 625 converter using a RAM.

Best wishes

Dave S

[krimskrams]

dear ausradiohistorian. i have reviewed many line tv videos, and i feel that i can build one myself now, especially since i have acces to a cnc mill. is there a good basic design plan that i can build mine on for experimental means?

kind regards

pete

[AusRadioHistorian]

No, it could not be improved to any great degree, except by reducing the perceived scan line transitions. Within a given bandwidth, the detail cannot be improved by upscaling. Digital transmission on HF is problematic, as the ionospheric path is dynamic, constantly changing, and return error correction is mostly impossible with ham-level technology. Digital image bandwidth compression is therefore no option and what you see here is the current limit of what one can send.

[DrBuzz0]

Surprisingly good quality for the 32 line resolution. If the receiver decodes this with software, it might improve it even more if it were upscalled. This, of course, won't increase the detail of the image, but it can make it easier on the eye and smoother looking

[AusRadioHistorian]

It would have the same effect, and be easier on CPU load, if controlled blurring was introduced ACROSS the line transitions, but NOT blurring ALONG the lines. Upscaling would involve a great increase in CPU load. That may be a problem with older computers having slow clock rates or limited RAM. The point of this is that these pictures can be transmitted in either a 5 or 10 kHz bandwidth dependent on picture repetition rate: the pics are not intended for viewing in full-screen size.

[DrBuzz0]

Yes, I realize that. The reason you'd use this would be to allow transmission of images over something like HF where you have very limited bandwidth and could never transmit conventional television. I'm just saying that if you were communicating using NBTV with another ham, the perceived quality could be improved on the receiver end.