Vintage SSTV transmit converter

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

Moderators: Dave Moll, Andrew Davie, Steve Anderson

Vintage SSTV transmit converter

Postby Harry Dalek » Sun Jan 07, 2024 11:36 am

Electronics Australia July 1990 Looking at some of my old magazines i came across this one not sure i have uploaded this one
Attachments
scan_20240107000240.jpg
scan_20240107000333.jpg
scan_20240107000419.jpg
scan_20240107000824.jpg
scan_20240107000710.jpg
Last edited by Harry Dalek on Mon Jan 08, 2024 4:16 pm, edited 1 time in total.
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Mon Jan 08, 2024 2:26 pm

Another good find Harry, maybe because it's from an Australian publication is the reason I've not seen it before. It looks entirely sane and easily 'buildable', the only hard part to find these days might be the CA3306 A-D. Though there are more modern parts that could take its place with a bit of a 'tweak' to some of the circuitry. Likewise the RAM (memory), though that should be a lot easier and still available from some suppliers...

The referred to Fig.3 (and 4) seem missing, or was in the subsequent article...

It would be an easy exercise to change the 74LSxxx series to the 74HCxxx series (having checked the pin-outs are the same, mostly they are) which would reduce power supply current.

As this appeared in an Australian publication I assume the video input is baseband 625/50...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Mon Jan 08, 2024 4:24 pm

Steve Anderson wrote:Another good find Harry, maybe because it's from an Australian publication is the reason I've not seen it before. It looks entirely sane and easily 'buildable', the only hard part to find these days might be the CA3306 A-D. Though there are more modern parts that could take its place with a bit of a 'tweak' to some of the circuitry. Likewise the RAM (memory), though that should be a lot easier and still available from some suppliers...

The referred to Fig.3 (and 4) seem missing, or was in the subsequent article...

It would be an easy exercise to change the 74LSxxx series to the 74HCxxx series (having checked the pin-outs are the same, mostly they are) which would reduce power supply current.

As this appeared in an Australian publication I assume the video input is baseband 625/50...

Steve A.


Whoops i forgot to upload it its now there the last picture file in the last post that will make a bit more sense !
It does look a little larger than what you have shown i suppose every thing gets smaller as the years go by .
Yes standard 625 line video in .
The CA 3344 is familar to me i wonder if i got one some time mmmm
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Mon Jan 08, 2024 5:30 pm

CA3344? Unless I'm mistaken I don't see any reference to it in the article....but easily missed...also not heard of it myself before...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Mon Jan 08, 2024 10:08 pm

Steve Anderson wrote:CA3344? Unless I'm mistaken I don't see any reference to it in the article....but easily missed...also not heard of it myself before...

Steve A.


Typo Steve i am mistaken CA3306
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby BruXy » Tue Jan 09, 2024 6:27 am

Hi Harry, nice find, archived as PDF here:

https://bruxy.regnet.cz/hamradio/SSTV_L ... er_-_1.pdf

(I did some automatic cleaning via Scantailor, but because of blurry parts where pages are not flat, I was not able to convert it just to monochromatic due to a loss of these parts, so the PDF file has approx. 27 MBs.)
User avatar
BruXy
Laboratory Assistant
 
Posts: 20
Joined: Thu Jan 30, 2020 1:43 am
Location: Halifax, Nova Scotia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Tue Jan 09, 2024 12:28 pm

Thanks for doing the clean-up on that article, much better now.

The main problem faced by anyone wishing to build a 525/625-to-anything convertor is the choice of the A-D. It has to be fast enough to digitise the source waveform. The CA3306 is certainly fast enough, but only 6-bits, OK for NBTV, maybe for SSTV too. It is also becoming scarce. A local supplier to me has 67 in stock at around US$4.00 each, once they're gone I guess that's going to be it.

There used to be an 8-bit version, the CA3308, but good luck with finding those...I have never seen them from any supplier, but someone somewhere might have some...though probably at an insane price.

There are suitable new versions available, but usually not in hobbyist-friendly packaging, generally SMD only.

It would be an interesting exercise to build this convertor with the original 74LS chips, then where possible replace them with 74HC versions and measure the drop in supply current. A lot of effort for just that experiment!

Steve A.

There is a way to make two CA3306s operate as a 7-bit A-D as shown in the datasheet. A compromise as ever as the speed might be reduced, but still fast enough for this application.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Tue Jan 09, 2024 6:33 pm

The 566 VCO is a rare chip also .
Yes its a lot of work for an experiment for sure and use but i suppose those with parts laying around never used may have every thing for some thing like this .
I am not sure i would have a go at it most of the parts would have to be in the parts junk box cost is a big part of a project .
I think as you say on similar different parts it may be possible but a lot of effort but i do like it !
As an exercise looking at the project every thing is fine so far parts wise to the A/D chip i just had a look whats about locally
and Jaycar sells these ADC0804 and DAC0802LCN D to A Converter IC
DAC0800LCN D to A Converter IC
If they work that would be a step forward you also mentioned a while back a replacement for the viewtopic.php?f=10&t=3182&hilit=analog+to+digital+converter
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Wed Jan 10, 2024 11:33 am

Unfortunately what's needed is a fast A-D device (Analogue-to-Digital). The D-A function is taken care of by U16 and the associated resistors. A PAL/625 active video portion of a line is 52us and that's all the time you have to do as many samples you wish to create the output. A microsecond to do a number of conversions, hence why fast.

What's needed is a replacement for U1, a CA3306. Depending on the exact version of CA3306 it can do 10-15 conversions in a microsecond. A sample rate of 10-15MHz, which is more than enough. An A-D which can sample at 2-3MHz would be fine. Even these 'slow' devices are hard to find in hobbyist-friendly packaging, i.e. DIL/DIP. SMD, no problem.

There's also a whole load of other matters than could be improved and simplified these days, but considering this was designed and built in the late 80s/early 90s, there was not the choice we have today. That's over 30 years ago!

The TLC5540 A-D I mentioned in the links above seems ideal from memory, I'll review it...and also see that it's still available...some chips go obsolete very quickly these days...Hmm, can't find a supplier of the DIL/DIP version at the moment, only SMD...though SMD-to-DIL/DIP adaptors are available from many parts suppliers...

Another alternative is the AD7822, in DIL packaging, 8-bit, 500ns/2MHz conversion rate. I do have a few of these in stock. Ideal for NBTV, but perhaps a bit limiting for SSTV resolution. Like all fast A-D devices, it's not that cheap at around 15 pounds each. Farnell/Element 14 list them, but no stock at the moment. RS are a no-go, not listed.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Wed Jan 10, 2024 7:25 pm

BruXy wrote:Hi Harry, nice find, archived as PDF here:

https://bruxy.regnet.cz/hamradio/SSTV_L ... er_-_1.pdf

(I did some automatic cleaning via Scantailor, but because of blurry parts where pages are not flat, I was not able to convert it just to monochromatic due to a loss of these parts, so the PDF file has approx. 27 MBs.)


OH i didn't know it was about ! Yes i see that page that was causing blur was just the printing i think i scanned it a few times to get the best result !
this was interesting too
https://bruxy.regnet.cz/hamradio/SSTV_L ... ._1981.pdf
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Wed Jan 10, 2024 7:51 pm

Steve Anderson wrote:
There's also a whole load of other matters than could be improved and simplified these days, but considering this was designed and built in the late 80s/early 90s, there was not the choice we have today. That's over 30 years ago!
Steve A.



Yes over 30 years go but for what it is its not to bad i looked into the CA3306 and the Ram ... LS ic's and they are all about on ebay via various sellers different countries even the 566 bit pricy but if you had a want it could be constructed .
Old yes but not old enough where the parts can't be got and you don't have to program the bugger !
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Wed Jan 10, 2024 8:46 pm

The 566 could be replaced with a couple of junk-box chips, it's nothing special in this application. The most crucial, important and almost irreplaceable component is the A-D, without that you have no chance. That's the crux of the matter. Finding one that's an easy graft into something like this, in a hobbyist-friendly package (DIL/DIP), meets the speed and cost requirements isn't easy....and also one that will be still be available in a decade or more from now. The CA3306 is from four or more decades ago...hence the scarcity...and possibly the stupid cost when you do find them.

As I mentioned recently, a stockist here has over 70 CA3306s in stock, and at a 'reasonable' price, around US$4.00 each. I'm willing to do a single bulk purchase if there's enough interest, i.e. for a 525/625-to-something convertor, at cost. I haven't done such a converter as yet, maybe others already have, but it's on my 'to do' list for an update...

It's simple. grab these chips while you can, I already have enough for what I want to do in the future..

A similar thing is happening to the LM1881, a FSTV sync-separator. Though not as critical (yet), sources are slowly drying up. In the article referred to here sync separation is done the 'old way', via Q4-Q6 in Fig.1.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Harry Dalek » Thu Jan 11, 2024 1:35 pm

Steve Anderson wrote:The 566 could be replaced with a couple of junk-box chips, it's nothing special in this application. The most crucial, important and almost irreplaceable component is the A-D, without that you have no chance. That's the crux of the matter. Finding one that's an easy graft into something like this, in a hobbyist-friendly package (DIL/DIP), meets the speed and cost requirements isn't easy....and also one that will be still be available in a decade or more from now. The CA3306 is from four or more decades ago...hence the scarcity...and possibly the stupid cost when you do find them.

As I mentioned recently, a stockist here has over 70 CA3306s in stock, and at a 'reasonable' price, around US$4.00 each. I'm willing to do a single bulk purchase if there's enough interest, i.e. for a 525/625-to-something convertor, at cost. I haven't done such a converter as yet, maybe others already have, but it's on my 'to do' list for an update...

It's simple. grab these chips while you can, I already have enough for what I want to do in the future..

A similar thing is happening to the LM1881, a FSTV sync-separator. Though not as critical (yet), sources are slowly drying up. In the article referred to here sync separation is done the 'old way', via Q4-Q6 in Fig.1.

Steve A.


Yes Steve i noticed the sync detection was done via the transistors and thought the same you could easy use a Lm1881 ...I ordered about 10 some time back . any thing like this might just want to do it classic keep it as is .
Looking at the data Sheet on the CA3306 D/A chip there are a few versions of it you put S i have not seen an S version for sale lots E versions
Yes the prices do vary on all the chips....I might have a look what i really do have laying around in my scrap boxes ,building some like this bit new to me but i see not impossible i stated this may as well finish it ! I do like its classic SSTV
Attachments
Screen 00027.bmp
Screen 00027.bmp (463.53 KiB) Viewed 1222 times
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 5374
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Thu Jan 11, 2024 2:36 pm

The last letter (and/or number) or two usually identify the package the chip is in, DIL, SOIC, etc..and like here also temperature and/or speed and accuracy. For our uses temperature usually isn't a problem, though speed and accuracy sometimes may be (though rare). The most important thing for us is usually the package/case.

For our use either the CA3306E or CA3306CE will do fine.

I intended the 'CA3306s' to imply plural, not another variant....i.e. three three zero sixes...hence the lower case 's'...English. Don't you just love it?....I may be English/British, but that doesn't mean I fully understand the language...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Vintage SSTV transmit converter

Postby Steve Anderson » Thu Jan 11, 2024 2:43 pm

Harry Dalek wrote:Looking at the data Sheet on the CA3306 D/A chip...


The CA3306 is an A-D device, easy to get A-D (Analogue to Digital) and D-A (Digital to Analogue) mixed up!

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5376
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Next

Return to SSTV

Who is online

Users browsing this forum: No registered users and 1 guest

cron