Retro SSTV anyone?

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: Retro SSTV anyone?

Postby Steve Anderson » Wed Aug 03, 2016 4:56 pm

Klaas Robers wrote:Steve,..I still don't know what you did in your demodulation channel.

Ah! Until I'm sure that I've got this right I'm keeping quiet on how I'm doing this. As I said before, it has probably been done previously though I've never seen any reference to it. It's no Earth-shattering modification of the Laws of Physics, just an idea I had after seeing the circuit diagrams of your 1973 SSTV monitor...40+ years later.

But I have to admit defeat in my aims to reduce the chip and pin-count. It's not excessive and on a par with the complexity of the robot 70 design, though maybe with further effort it could be simplified without compromising performance.

The headache is the sync detection performance, if you don't mind the 'jitters' then it's just two 8-pin chips and a handful of passives...as per previous screen-shots. On a small screen you may not even notice the 'jitters', but on a medium-sized TV you sure do! On a small screen you're unlikely to notice the improved resolution too.

As of this evening I'm off to Changsha in China.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4397
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Retro SSTV anyone?

Postby Klaas Robers » Fri Aug 05, 2016 4:32 am

Steve,

if solving the jitter problem in the deteection of the 1200 Hz is too difficult..... and I expect that the way you are going, that it is impossible to solve it, as your method is subcarrier locked..... Then you may solve the unavoidable jitter problem by making the suggested fly wheel on the jittering sync. The flywheel eliminates the jitter due to its innertia.

Firstely use a separate PIC for it and afterwards it might be possible to merge this with the 1200 Hz sync detection in one PIC. Anyway I am interested in the flywheel, as I need it too to remove the remaining jitter in my analogue sync detection circuit.

Good luck.
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1540
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV anyone?

Postby Viewmaster » Tue Aug 30, 2016 5:21 pm

Why is SSTV named thus for as I understand it only static images are sent about every 2 seconds?
That is not television is it?
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1292
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: Retro SSTV anyone?

Postby Harry Dalek » Tue Aug 30, 2016 6:57 pm

Viewmaster wrote:Why is SSTV named thus for as I understand it only static images are sent about every 2 seconds?
That is not television is it?


Hi Albert
7 or 8 sec 120 128 line its a bit more like fax which i think was pretty much AM but SSTV is FM
Television in that it used a P7 CRT at the start not printed on a sheet as Fax well apart from one design !

Heres some experiments i was doing some time back its a little bit like what you are up to now ....

viewtopic.php?f=8&t=1890&start=120
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: 4565
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV anyone?

Postby Viewmaster » Tue Aug 30, 2016 7:50 pm

WOW, Harry, you are a mechanical wizard, sir.
I really admire your tenacity.
Showing moving gears on the forum too!

I haven't seen any of that before due to my attention being on
other things these past two years or so.

Seems that I have a great lot of catching up to do. :)
But at 83, where the hell do I get the time for it? :lol:

I guess that as television is seeing at a distance then SSTV can be called SSTV
but it's not how we ever thought of TV, even back in the old days of NBTV.
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1292
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: Retro SSTV anyone?

Postby Harry Dalek » Tue Aug 30, 2016 8:47 pm

Viewmaster wrote:WOW, Harry, you are a mechanical wizard, sir.
I really admire your tenacity.
Showing moving gears on the forum too!

Hi Albert
The mechanical camera in all its forms really interests me i was thinking a Slow scan one would be easier ,as far as camera scanner i have got it down to a tee ,but a direct light one i only got a fuzzy image which is better than none ...at least incentive to think and plan .
The problem of the mechanical vertical scan i think you saw if i have some thing to repurpose i am ok at it but i am not good at making stuff from scratch !

I haven't seen any of that before due to my attention being on
other things these past two years or so.


I forgot about it but when you were asking about SSTV got me thinking on your design something there might be helpful .

Seems that I have a great lot of catching up to do. :)
But at 83, where the hell do I get the time for it? :lol:


Albert i sure hope i make it to 83 and still have your drive to enjoy this stuff ,i bet the wife shakes her head as mine !

I guess that as television is seeing at a distance then SSTV can be called SSTV
but it's not how we ever thought of TV, even back in the old days of NBTV.[/quote]

Yes true but they never called it that in the facsimile days being printed and Slow scan many years later displayed on a crt is very different closer in the way its displayed to normal television than Fax via paper .
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: 4565
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV anyone?

Postby Viewmaster » Tue Aug 30, 2016 10:49 pm

Harry Dalek wrote:The mechanical camera in all its forms really interests me i was thinking a Slow scan one would be easier ,as far as camera scanner i have got it down to a tee ,but a direct light one i only got a fuzzy image which is better than none ...at least incentive to think and plan .
The problem of the mechanical vertical scan i think you saw if i have some thing to repurpose i am ok at it but i am not good at making stuff from scratch !
.


I couldn't quite make out how you vertically scanned. I believe you have rack and pinion
with tilting table which is the way to go.

Great minds think alike, Harry :lol: ..........my laser will be fixed to the top
platform and a tiny spinning mirror (up to say 6000RPM or so) will
scan the laser fast around360 degree.

Looking at my PC speed I will be able to draw on screen about 12,000 pixels per second

For sync I am using my Edikow sync method. A separate disc with ONE sync hole in it.
The fixed opto can be moved around to any position so the sync point can be moved
to get the 0 to 360 degree line width !!

Ain't mechanics just so exciting, Harry :lol:
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1292
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: Retro SSTV anyone?

Postby Harry Dalek » Tue Aug 30, 2016 11:49 pm

Hi Albert

I couldn't quite make out how you vertically scanned. I believe you have rack and pinion
with tilting table which is the way to go.


I did it a few ways Albert first easy way my hand ! slow scan is slow enough to just move the light sensor down by hand close to the rotating image later on i used the idea in the animated gifs below old dvd or cd rack mechanism and changed it a bit for fly back /as you see i got it to work one try before i went on to try another scanning idea ( a touch to fast for Slow Scan notice the picture fly back was to soon and started the next scan image ).

Great minds think alike, Harry :lol: ..........my laser will be fixed to the top
platform and a tiny spinning mirror (up to say 6000RPM or so) will
scan the laser fast around360 degree.


Are you using a 4 sided mirror would be way to go Albert ,as we know more mirrors slower it has to rotate ...lego blocks are good for the mirror mounts ...i also found the blocks are very reflective untouched .

Looking at my PC speed I will be able to draw on screen about 12,000 pixels per second


That sounds pretty good to me ,its going to be a very fine image.

For sync I am using my Edikow sync method. A separate disc with ONE sync hole in it. :mrgreen:
The fixed opto can be moved around to any position so the sync point can be moved
to get the 0 to 360 degree line width !!


This is similar to my rotating image but you are doing it much harder than my rotating picture tubes and squares as a flying spot camera ,,,,i didn't really sync the the horizontal line speed stepper apart from my eyes checking the speed the steppers are much better at keeping speed than a DC in manual control .
Ain't mechanics just so exciting, Harry :lol:[/


Yes very much so ! :mrgreen:
Attachments
MVI_0340.gif
MVI_0340.gif (2.07 MiB) Viewed 7836 times
MVI_0357.gif
MVI_0357.gif (4.98 MiB) Viewed 7836 times
MVI_0358.gif
MVI_0358.gif (5.96 MiB) Viewed 7836 times
Screen 00185.jpg
Screen 00185.jpg (44.3 KiB) Viewed 7836 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: 4565
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV anyone?

Postby Viewmaster » Wed Aug 31, 2016 3:23 am

Harry, I do like the fast flyback you have achieved. Very neat.

Re a 4 sided mirror. Yes, although one can get more scans per rev
I'm not sure whether one could get a full 360 degree laser scan
using 4 mirrors.
I have though considered thin reflective foil used as a 2 sided mirror.

I am torn between quite a few roads to go before deciding which one.

One thing is for sure. I am dying to see a full 360 degree picture on screen.
Also being able to have varying number of lines per frame too.

I blame all this on you, Harry. :)
If you hadn't given that Cambridge link I would still
be outside gardening ! :lol:
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1292
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: Retro SSTV anyone?

Postby Harry Dalek » Wed Aug 31, 2016 6:27 pm

Hi Albert
Whoops sorry about that Albert i am a Gardener by trade so not much help here but if i were over there i do some hedging for ya ! :wink:
Yes i forgot you are doing 360 image ...mmm i am not sure a mirror would reflect a laser all that way i could be wrong as i am many times ! :shock:
How about rotating the laser ?
viewtopic.php?f=8&t=2001
I will explain....in this shelved project using rotating light sensors due to vibration at speed you could use the idea to use laser instead in a simple powering the a rotating laser by induction ,does not have to be a vcr rotary transformer you can make your own simple coils as in the led powered by induction.
Feel free to go you own road on your project just chucking some ideas around if you have trouble with the mirror idea .
Attachments
DSCF4968.JPG
DSCF4968.JPG (282.69 KiB) Viewed 7824 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: 4565
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Retro SSTV anyone?

Postby Viewmaster » Wed Aug 31, 2016 10:30 pm

Harry, thanks for reply but we are getting your SSTV thread mixed into my 360 degree thread.
So I have answered you in that thread.

viewtopic.php?f=8&t=2158
This will no doubt soothe the moderators frowning brow too. :lol:
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1292
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Re: Retro SSTV anyone?

Postby Steve Anderson » Tue Feb 14, 2017 1:02 am

After an absence of well over six months it's time to pick up this thread again. Part of the reason for this is that I've been contacted by Chis Lewis who is interested in the the original Cop McDonald SSTV standard (only). He's keen to replicate what I've done so far...I say no more.

As yet I'm reluctant to unleash this upon others until a few things are sorted out. First and foremost is the demodulation process which I'm somewhat dissatisfied with. The updated Robot 70 demod works, yes, but it shows its 1960s antiquity. My own efforts into software demodulation have yielded mixed results with the major flaw being sync-jitter, though the actual video demod does show an improvement.

I'm also in the mind-set to replace the two micros with more modern devices (they also happen to be much cheaper) and drop the logic supply volts down to 3.3V instead of 5V, saving power, not that that is a great concern to most anyway.

So a few weeks and things may start to appear here. I have other matters to attend to in the meantime, none unfortunately relating to this forum.

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4397
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Retro SSTV anyone?

Postby Klaas Robers » Thu Feb 16, 2017 6:57 am

Welcome back Steve.

Good to know that Chris is interested in the original SSTV standard. I planned more or less to visit the NBTV Convention in April, and then I will see Chris. Now that I know he is particularly interested, I could plan to bring my "Heathkit SSTV monitor" to England for that occation, now that country is still part of Europe; next year it might be more troublesome. Then he can see the Radar picture tube in operation. It is more or less a pity that my filters are designed around the Philips pot cores, which are difficult to get nowadays. So copying my circuits is not an option for today. On the other hand, if he likes it, I have still a spare 7BP7 and a 5FP7 and I have an extra 70 degrees deflection yoke for him. I will contact him about it......

I am still curious about your software demodulation, I hope that after it works that you are willing to share it with me.
User avatar
Klaas Robers
"Gomez!", "Oh Morticia."
 
Posts: 1540
Joined: Wed Jan 24, 2007 8:42 pm
Location: Valkenswaard, the Netherlands

Re: Retro SSTV anyone?

Postby Steve Anderson » Thu Feb 16, 2017 3:08 pm

Yes, I'm sure Chris will be interested in your monitor. He has said he will dig through this thread so I'm sure he'll come across it.

The use of pot-cores has fallen into decline with the ease of using op-amps and non-inductive passive components. There are trade-offs, sure, but generally op-amps use less board-space, don't need the winding process of inductors, in a nutshell, a cheaper solution commercially...they do however require power.

As for the software demodulation, when I'm happy with it I quite willing to openly release the software, there is little or no commercial value in it. It all depends on the amount of time I have available. After nearly six months working on an Australian TV project, then going to the UK in mid-January for three weeks, I come home and find another project in Jakarta waiting for me. No peace for the wicked it seems...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4397
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Retro SSTV anyone?

Postby acl » Sun Feb 19, 2017 9:48 pm

Hi there Steve and Klaas,

When it is in a suitable form to release I would be very interested to build one for myself. I wish I had taken up Grant Dixon's offer of some of his old SSTV gear before he went to live with his son. I did get his scan converter. There seems to be some revival of the original SSTV 8 Second black and white technology. I have recently built a transmitter using an Arduino Due and used a Raspberry PI to decode SSTV using a Linux program called QSSTV. Klaas you are always welcome to stay over at my house when you visit Brexit Land even if the cost of living is slightly higher now. :D
acl
Just nod and pretend you understand me
 
Posts: 209
Joined: Thu Mar 08, 2007 7:38 am

PreviousNext

Return to Cop McDonald's FM SSTV System

Who is online

Users browsing this forum: No registered users and 1 guest