SSTV-625 Up Converter MkV (Five)...

Where it all started as far as most are concerned and saw heavy use from the 60s through to the 80s. Colour and Hi-res modes have unfortunately pushed this system into the backwaters of SSTV. Time to resurrect interest in this simple analogue system.

Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Sun Apr 25, 2021 5:15 pm

R.E. Variable duration and pixel quantities...posting of last Sunday, April 18th in this thread...

Well, no-one (yet) has come forward and said, "What dumb idea." so I guess it might be a valid proposition? I can't see any reason why not...but it may come back later to bite me on the bum!

Now...how to do it? "Wench - more beers."

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Harry Dalek » Sun Apr 25, 2021 9:07 pm

That's interesting the 1 and 5% resistors tests similar results or very close ,i like the idea of a few test runs just in case post or so back ...
Keep at it Steve still watching ...might be an idea to ask who else is i am sure there are others who like me can't really post due to your one of the few people who can do this so we can't help .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Mon Apr 26, 2021 3:43 pm

Well, this, (SSTV), is a very minority interest, so I've never expected hoards of people to be partaking or even interested. However, some of the techniques and ideas may have an application within NBTV and could be inspiration for others.

However, once this is done my next project here will be specifically NBTV themed. I've already done some unpublished work on it a while back. But this SSTV project isn't going to be done quickly, there are still a number of hurdles to overcome whilst still making it practical for others to copy/build/modify/improve.

I now have quite a bit of time to get on with this, the last nine months or so have been hectic with other things not related to our interests here. But they occasionally have a spill-over of ideas into what we do here.

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Harry Dalek » Mon Apr 26, 2021 8:58 pm

Pretty much all the forum ideas are very of a narrow interest only for the connoisseur of hobbies ! :wink:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Tue Apr 27, 2021 3:06 pm

Nice expression! "connoisseur of hobbies"....

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Thu Apr 29, 2021 3:46 pm

I've just realised the title of this thread is incorrect! It should be "SSTV-VGA Up-Converter MkI", with no mention of 625 or 525. It's mutated from a 625 output into 800x600 VGA. I'll start a new thread to clarify matters. I won't lock this tread for now, but maybe in a month I will.

The continuation thread will be "SSTV-VGA Up-Converter MkI".

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Harry Dalek » Fri Apr 30, 2021 8:05 pm

Steve Anderson wrote:I've just realised the title of this thread is incorrect! It should be "SSTV-VGA Up-Converter MkI", with no mention of 625 or 525. It's mutated from a 625 output into 800x600 VGA. I'll start a new thread to clarify matters. I won't lock this tread for now, but maybe in a month I will.

The continuation thread will be "SSTV-VGA Up-Converter MkI".

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On the discontinued video formats for Television as in plugging things into a monitor or more so for a television these days as we have all noticed we have never had more of choice of different formats than today to plug into a Tv .
But for computer monitors i think its going to go the other way fast where nothing is plugged in its all wireless .
Some future constructor might have to work out away around this if TVs go the way of computer monitors ...plug in cables seem to be on the way out and that's no fun ! OH well i will stay in my rut i like the past and keep it alive .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Sat May 01, 2021 11:51 am

Harry Dalek wrote: ...plug in cables seem to be on the way out and that's no fun ! OH well i will stay in my rut i like the past and keep it alive .

At the moment it's 'the thin end of the wedge', but it's inevitable I think. Multi-conductor cables and their connectors cost money, the components for a wireless link will become cheaper than cables in time.

But there's the security issue to address, how to stop your neighbour seeing what you are? Financial statements, or simply 'awkward' e-mails...we won't go there.

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Thu May 06, 2021 5:08 pm

For a number of reasons I'm placing this project 'on-hold'. Most significantly a paid project that perfectly overlaps a NBTV project I started some time ago has landed in my lap. Expect to see a resumption of the DC-coupled NBTV PC recorder (or whatever I called it) very soon.

I will resume this thread when the above is complete...I am on a fixed timeline so it shouldn't be that long an interruption...

The original thread was called "Negating LF problems of NBTV.", which I will continue...in the 'Electronic NBTV' section...I started it just over a year ago, this SSTV-VGA thing has distracted me...

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Sun Jul 18, 2021 3:55 pm

Just like a few other items here, this is suffering from the global chip shortage. Though in the news it appears things are improving for auto manufacturers, us lot are way down the food-chain and will have to wait somewhat longer...

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Sun Sep 12, 2021 8:02 pm

I've refreshed my mind on where I got to on this...a large amount of simplification has already happened without hopefully compromising results. No more +/-12V supplies needed, just two +5V (one analogue, one logic) and one -5V (analogue). The largest chip packages are the two micros, both DIP-28. This is for 800x600 60Hz VGA output, a worldwide standard (though quite old). The actual display will occupy 512x512 of those pixels on screen. Though the MkI was 256(H)x512(V) on-screen due to the interlacing, the resolution was still 128x128...as of course this will be...

One of the challenges was dealing with the interlacing, which actually turned out to be my friend...however, few PC display modes are interlaced...hence the wider bandwidth required...not transmitted, just a metre or two of cable, easy.

One other thing to consider, a 800x600 VGA should be displayed correctly on a modern 16:9 monitor with black bands either side, though that's not for certain on older CRT 16:9 devices...what a mess!

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Mon Sep 13, 2021 4:36 pm

A bit of a 'Eureka' moment this morning - I may be able to get this down to a single PIC processor! I'm not holding my breath, and neither should you! It'll still be a single PIC18F26K22 (28-pin DIP/DIL) or perhaps one of the newer PIC18Q... series...though I'd need a new programmer and software for those...

...I'll stick with the PIC18xxx series for the moment...though the 16-bit versions are very tempting...this may be the last 8-bit project I do...I've already done 16-bit stuff for clients, time to move on...

...however, I still have an urge to do something with a MC6809, very retro, 8-bit, 1970s, external RAM, external program storage, basically external everything! It's the first micro I ever hardware designed and programmed, sometime in the early 80s...the chips are still available here at reasonably sane prices..

Anyway, I digress...again....

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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Thu Sep 16, 2021 4:50 pm

I mentioned elsewhere that the memory/output for this has been updated, so here's the current state of play...

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SSTV-VGA MkV Main 1 v8.gif
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Re: SSTV-625 Up Converter MkV (Five)...

Postby Steve Anderson » Fri Sep 17, 2021 3:08 pm

...a further update, added some buffers (74AC(T)125) to drive the HS & VS outputs. The micro is a bit marginal in delivering 8mA to the VGA sync inputs.

I'm getting to the stage where I should be able to display a fixed test-pattern on a VGA 800x600 60Hz monitor. First, "Clear the decks"...there's a lot of stuff I need to clear away! As well as buy some basic stuff, like 15-pin hi-density VGA connectors...

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Graham Lewis's NBTV to VGA converter

Postby acl » Fri Sep 17, 2021 10:22 pm

Hi Steve,
I just dug out my NBTV to VGA converter designed by Graham Lewis.

Regards Chris Lewis
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