NBTV/SSTV-625 Up Converter MkIII

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: NBTV/SSTV-625 Up Converter MkIII

Postby Steve Anderson » Tue Jan 28, 2020 3:56 pm

On a different note, though certainly applicable here, anyone know where to get CA3308 ADCs? They're the 8-bit version of the 6-bit CA3306 ADC used in converting FSTV to NBTV or SSTV. There are other more modern variants around but none quite match the speed and simplicity of these two devices. I have the datasheets for both and they work in exactly the same manner and at the same speeds, the CA3308 simply has two more bits...pdf attached...

I have trawled the 'net without much success, but I'll keep trying...though I'm open to other devices/suggestions...

Steve A.
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Re: NBTV/SSTV-625 Up Converter MkIII

Postby Klaas Robers » Tue Jan 28, 2020 7:02 pm

I tried Conrad, as they sometimes have still older ICs. But no CA3308 or CA3306 known.....
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Re: NBTV/SSTV-625 Up Converter MkIII

Postby Harry Dalek » Tue Jan 28, 2020 7:44 pm

I found these same code but not what you are after
https://www.ebay.com.au/itm/CA3308T-IC- ... ctupt=true


What about these ?
https://www.ic2ic.com/search.jsp?sSearc ... 8&prefix=C

What about the CA3306 ? is that the same thing ?

https://www.aliexpress.com/af/ca3306.ht ... 0128005153
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s-l1600.jpg
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: NBTV/SSTV-625 Up Converter MkIII

Postby Steve Anderson » Wed Jan 29, 2020 1:46 pm

Thanks for the effort Harry but I already have a few CA3306's, they are the 6-bit version. I'm hoping to find the 8-bit version, CA3308.

The photo shows a T099 device and although the type number looks correct, they can't be, the CA3308 is in a 24-pin 0.6" DIL package, so who knows what those TO99 devices are! And look at the shipping, ridiculous for something that weighs only a few grams!

Thanks again Harry but I'll keep looking.

If I can't find any I'll simply have to use a more recent device...

Though two CA3306's can be cascaded to form a 7-bit ADC which may be OK.

The Maxim MAX1191 is ideal and a sane price, but in a SMD package which is one of the most human-unfriendly types, SOIC is OK, but not this!

Steve A.

Crappy photos on that site, why did they bother? Here's a similar photo I just took using my inexpensive Vivo 'phone...f2.2, 1/33s, ISO400, 31mm focal length, hand-held. The markings (LM357 etc.) are on the side of the device...the coin is 20mm in diameter, a 1 Baht coin from here...around three cents US.
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Re: NBTV/SSTV-625 Up Converter MkIII

Postby Steve Anderson » Fri Feb 07, 2020 4:31 pm

Gents, I have a confession to make and I cannot believe that others haven't picked up on my stupid error!

For this SSTV (or NBTV) converter to 625 we DO NOT need a fast A-D. The internal A-Ds in the PICs are plenty fast enough and 10-bit. What in the heck was I thinking of? That's if we need an A-D, if we use the pulse duration method to measure the SSTV frequency we don't need an A-D at all, just a comparator, also within the PICs.

So all that previous stuff about CA3306's and CA3308's is a load of old twaddle!

I think the Christmas and New Year spirit must have got to me! (Weak excuse). Unless I was prattling on about something else, i.e. somewhat off-topic, which is nothing unusual for me!

In my defense I have got the circuit diagrams correct, I must have some corrupted neurons in the grey matter!

Steve A.

Note to self: Keep it on-topic in future!...and THINK before you post!

Ah! My posting here of Jan 28 does actually exonerate me! All the same I can't think why I was looking for these devices...NURSE!
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Re: NBTV/SSTV-625 Up Converter MkIII

Postby Harry Dalek » Fri Feb 07, 2020 6:25 pm

That's Ok Steve mistakes are a good thing never learn a thing without them ~! Just watching seeing how it go's less ic's are a good thing !
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: NBTV/SSTV-625 Up Converter MkIII

Postby acl » Fri Feb 07, 2020 7:22 pm

Keep up the good work Steve. Looking forward to your progress.

Regards Chris Lewis
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Re: NBTV/SSTV-625 Up Converter MkIII

Postby Steve Anderson » Thu Feb 13, 2020 4:26 pm

Sadly work on this MKIII Up-Converter has almost ground to a halt due to a large work project I'm involved in. Location - The Maldives, yea, that's OK, I'll suffer it for a while...

When i get time I'll continue on with the design phase, but with no workshop I can't prototype anything...

But anyway, in the past there's been discussion of the use of 525 lines as a source of down-converted material to SSTV. If you look at the 525 line/field/frame spec attached there are 242 complete lines in an NTSC field (Field 1 or 3). If we use every other line and only use 120 of them then append eight lines of greyscale (or anything else), we end up with a 128-line SSTV picture. If not we still end up with the Cop McDonald 120-line standard, either at EU or US SSTV format.

Now the hiccup may be that inexpensive TV cameras may not adhere to these broadcast standards - there's only one way to find out...

Steve A.

625 down-conversion is comparatively easy...and doesn't require the greyscale, but can be added if required.

The attached was from this site...If interested I suggest you download all you might need in the future before it vanishes...(Windoze - right click - save as..Webpage or Website complete, HTML).

https://web.archive.org/web/20080220113 ... index.html

For NBTV'ers I still have that in mind and it should be comparatively simple...except if you are in a 60Hz country, that's awkward...
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