Slow Scan Television Experiments

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.

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Re: Slow Scan Television Experiment

Postby Harry Dalek » Mon Mar 02, 2015 10:27 pm

Have not posted for a while here not for lack of interest but for the old problem its not cooperating with my design flaws to put it kindly :(

I nearly tried using a lens disk see picture (idea didn't get passed this stage i could see really it would of been giving similar results to a mirror reflection anyway ) my interest really is still working out the mirror side of things hate to give up fingers crossed for year 2.

The little i have on what is said to have worked i have been reviewing .

Looking at what is different to what i have been trying , 2 other Nbtvers ideas the mirror drum doesn't use a lens before the mirror ,so this is different for me ,the image is then focused to an opaque plate with a pixal sized hole with the photo sensor adjusted behind this.

I can see the reason for the tiny hole in the plate but it really bothers me about the light loss and sort of turns the mirror drum into a stationary nipkow wouldn't the light loss be worse than a nipkow camera ?

Suppose if it works its fine but i am surprised a tiny lens is not used here .

If i were to try the tiny hole in the plate i know my head amp would need lot more light .

I have set up my camera in the shed for further experiments and changes ,i will look into getting mine close to these ideas see what happens .
Attachments
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only tried a few light tests with one ,back to the mirrors
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Screen 00011.jpg
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Screen 00000.jpg
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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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Harry Dalek
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Re: Slow Scan Television Experiment

Postby Harry Dalek » Sat Mar 07, 2015 8:31 pm

I had some time today to try out a few mirror ideas nothing really successful but it could be i am looking at the problem the wrong way around .

I should of taken a few pictures as i tried every thing from masking off the square mirror to a slit vertical horizontal changed the mirror size number of mirror faces so on.

The only thing that really worked to some degree out of focus was the tiny lego long thin mirror that i tried some time back so i suppose instead of trying to work out whats wrong with a mirror size with more width i should look more into this .

Any case i also had time to do a quick test of my sensor head amp in a quick Flying spot 8 sec sstv experiment ,i used some letters on some Transparent plastic placed that over the scope screen adjusted the scopes horizontal to sync with MMsstv program set at 8 second feed via the head amp /

Took the lens off the sensor pointed it at the scan line and moved both vertical on the scope and as best i could the sensor with the scan line as i adjusted it down to scan the home made slide ........the sensors viewing angle was narrow but i did get results seeing the SSTV letters written on my side first go .

I will tried it out again on a better scope that i can adjust brighter and see if i can get better results ,seeing this today i can see doing this mechanically with a laser should give good results.

In a way all my experiments i have been using a lens on the sensor for close up drum scanning i have noticed others don't use a lens on the sensor at all could be my problem trying the direct light experiments ,i'll also look into this .
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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Harry Dalek
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Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Mar 08, 2015 6:16 pm

I had a look more into the quick and dirty flying spot slide scanning today.

I swapped my photo transistor for the TIL78 no other reason i bought a lot of them some time back and time to test !

I took some photos and screen grabs so you can see the results ,i am interested to see if i can do a slide picture the light in my shed was
a bit bright so i will leave that for a night experiment .

This slide is a little easier and i worked out the distance to view it in full .

I did play around with mirror camera idea also today i can see i have a bit of work on this side of things ,i managed to get a dreadful out of focus image with a picture close to the mirror ( i only used one mirror face and had drawings on the other faces of the square to test for an image and focusing ) The light levels need to be different for either the mirror reflection or drawings .....my interest is the mirror side of it since its my Achilles heel.

I can just make out the shape of the space lady it looks to me like the longer the mirror to more squashed the image as i can only get so close with out trying a lens with the tiny long mirror i tried many a post ago you can get very close to the mirror and focus is bad still be much better than this .

I also while i worked this out tried to view or scan the drawings on the other faces of the square bock via a mirror reflection to see if the dreadful focusing problem was a problem for sure this way around also and it is ...if any thing i see the problem to be looked into now .
Attachments
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quick and dirty slide sstv scope to pc
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1 00020.jpg
a little slewed but i managed to get it all
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anigif.gif
My tests a little left a little right a little forward back more shading adjust levels so on .
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IMG_0475.JPG
TIL 78
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my test on this today
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the 3 faces with drawings last is mirror
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very thin out of focus space lady
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1 00002.jpg
no2 try just as bad
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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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Harry Dalek
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Re: Slow Scan Television Experiment

Postby kd2bd » Thu Sep 29, 2016 1:14 am

Steve Anderson wrote:Thanks for the links Harry, but all are based on the MMSSTV engine, i.e. it's gonna require the VIS signal at the start of each frame.

There is one site I found a few weeks ago that looked promising at first - forget the complexity for the moment, but I have my reservations as to the claims made. I hope that I'm proven wrong...

http://www.qsl.net/kd2bd/sstv.html

..and the site specific to his converter...

http://www.qsl.net/kd2bd/TriplePIC.html

...but at least we have a.n.other who's also interested.

I have been in contact via e-mail with him, but he's giving nothing away, perhaps as a result of his agreement with 'ATV Quarterly' which is understandable.

Steve A.

You'll also note that all is under 'perfect' signal conditions, no noise, fading etc...


Hi Steve (and everyone else).

Here are all the details regarding my scan converter.

Enjoy! :D


73 de John, KD2BD
Attachments
TriplePIC_article.pdf
KD2BD TriplePIC SSTV Scan Converter
(3.3 MiB) Downloaded 234 times
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