Mechanical video recorder

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Re: Mechanical video recorder

Postby Klaas Robers » Mon Oct 14, 2019 11:00 pm

One of the major problems Baird had is that the recording / play-back process on 78 rpm records works only more or less well at a speed of about 80 rpm (so: 78 rpm) The material did not work good enough at higher speeds, e.g. 160 rpm. Then he came to a system with about 5 frames per second. This might have been because also Baird had problems with the higher frequencies on a mechanical record. You are not the only one.

But if you run a Nipkow disc at that low speed your eyes just see a moving line, not a picture. Your eyes can follow the line and that is what they DO. Nowadays with some digital memory we can store the lines and show them as a still picture. And that is what Don McLean did. But even the long persistence CRTs that we used for displaying SSTV were not existing in 1930.! Baird had a hard time.
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Re: Mechanical video recorder

Postby Viewmaster » Mon Oct 14, 2019 11:27 pm

Harry, I think that this technique has already been mentioned here, but.....
…….I am building 2 seismographs with very low freq o/p's. ( can be more than 1 sec)

So in order to handle this I am modulating a 5kHz sine wave with the low freq.
Then feeding this into such as Audacity where the 5kHZ will not be seen,
but just the low freq 'waves' riding on top of the 5kHz as it were.
I wish I had tried this on my Edikow machine, way back, as 5kHZ sine wave was easily
recordable
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Re: Mechanical video recorder

Postby Harry Dalek » Tue Oct 15, 2019 7:40 pm

Klaas Robers wrote:One of the major problems Baird had is that the recording / play-back process on 78 rpm records works only more or less well at a speed of about 80 rpm (so: 78 rpm) The material did not work good enough at higher speeds, e.g. 160 rpm. Then he came to a system with about 5 frames per second. This might have been because also Baird had problems with the higher frequencies on a mechanical record. You are not the only one.


I think at the time there was only 78rpm ? i know some one else wanted longer play record recording and invented 33 rpm ..45 rpm you would think would of been the next step but this i am not sure of ...a do have an old player that has 16 rpm i am not sure how popular that format was ?

But i am meaning 78 rpm would of been what was in at the time and would of been logical to use what people had for play back ...I can do 78 rpm with my lathe ...I forgot he dropped the frame rate ....!

You would think higher the speed better the quality and bandwidth you can record but i would think play back would of been the big problem and record time .
Now you have got me thinking i can make this format 30 line 5fs thanks to the FreeNbtv software !

Still there were home recordings from some one in Sweden if i recall right ? off air via a record lathe this would of been the normal Baird 30 line BBC format .

But if you run a Nipkow disc at that low speed your eyes just see a moving line, not a picture. Your eyes can follow the line and that is what they DO. Nowadays with some digital memory we can store the lines and show them as a still picture. And that is what Don McLean did. But even the long persistence CRTs that we used for displaying SSTV were not existing in 1930.! Baird had a hard time.


I can see why he never ever went back to trying to record video it must of been a nightmare and he was working more than just this at the time as well ...i can see all the problems ...
Closer to out era 2006 Jeremy Jago did it from page one and Albert so that gives me hope !
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Re: Mechanical video recorder

Postby Harry Dalek » Tue Oct 15, 2019 8:09 pm

Viewmaster wrote:Harry, I think that this technique has already been mentioned here, but.....
…….I am building 2 seismographs with very low freq o/p's. ( can be more than 1 sec)


Hi there Albert no if so that slipped my mind ! i do wonder what you get up to i was reading the the musical Tesla device you were working on a while back

So in order to handle this I am modulating a 5kHz sine wave with the low freq.
Then feeding this into such as Audacity where the 5kHZ will not be seen,
but just the low freq 'waves' riding on top of the 5kHz as it were.
I wish I had tried this on my Edikow machine, way back, as 5kHZ sine wave was easily
recordable


My last test was a sweep to 10 KHZ i was thinking to use Jeremy Jago cassette recording idea to am modulate NBTV to the carrier and have a demodulation after it would fix the problem of recording low frequencies over riding the higher .

Its not the Baird way but it is record recording ...

Recording the classic way i can see as far as the sync pulse go's widening the pulse a touch would let it be recorded better for playback even some thing like we use a schmitt trigger would be useful playback for reshaping the pulse ..some filters to adjust the frequency levels before recording perhaps ...lots of ways to go and experiment heads spinning .

I may go back to SSTV and the carrier idea can be 1khz i have done this on ultrasonic transmitting .

So 2 roads to take either classic Baird or carrier idea Albert
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Re: Mechanical video recorder

Postby Viewmaster » Tue Oct 15, 2019 8:49 pm

I cheated on the recorded sync pulse problem as you know, Harry, and completely sidestepped it.
Became quite adroit in side stepping. :)

Just to recap....I ensured that there was an EXACT number of frames per rev. (2)
Then using using the adjustable radial angle of a mechanical pulse generator I was able to put an artificial
sync pulse just where I liked within a frame on playback.
So a recorded sync pulse was not required.

You can do the same if your recorded sync pulses don't work for you.
Take up side stepping, Harry. :lol:
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Re: Mechanical video recorder

Postby Harry Dalek » Tue Oct 15, 2019 10:17 pm

Viewmaster wrote:I cheated on the recorded sync pulse problem as you know, Harry, and completely sidestepped it.
Became quite adroit in side stepping. :)


Not cheating Albert Baird didn't use one at all just geared the the camera to the record lathe ..your way was not easier just different .

Just to recap....I ensured that there was an EXACT number of frames per rev. (2)


I didn't ask that Question what was the frame rate you used ? standard NBTV ?

You also had a high speed recorder as i recall .. what record time did you have there abouts ?

Mines all adjustable i just go standard as i have no playback arm at the moment i pinched if for the lathe recorder ! it fixed my recording problems so was needed .

Then using using the adjustable radial angle of a mechanical pulse generator I was able to put an artificial
sync pulse just where I liked within a frame on playback.
So a recorded sync pulse was not required.


Its a good idea it looked like a beast of a machine Albert to get right but you did it !

The cylinder is a better recording idea as i can see speed change as i get towards the middle end of the recording disc this is not good at all ! just have to put up with it as a bit like those with a nipkow monitor see slanted image where if it were a cylinder you would have the correct aspect ratio .
me it will cause syncing problems a manual adjustment will have to fix that

You can do the same if your recorded sync pulses don't work for you.
Take up side stepping, Harry. :lol:


Well i know the sync can be recorded i have done it its more its pulse width can not be to narrow ..its more recording frequencies in the video the lower frequencies record to loud so stuffing up the higher frequencies ..the lathe also tends to record sine wave like rounding the waveform must be similar to what you saw trying in your experiments Albert ?
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Re: Mechanical video recorder

Postby Harry Dalek » Fri Oct 18, 2019 8:26 pm

Doing 2 Tests today another longer 30 sec sweep test and a full recording trying to record 10 KHZ i found my stepper motor i am using on the lathe starts to play up towards to 10khz even with out recording i can hear the resonance's come and go ...this means another redesign .
Gone back to the tweeter idea really an old lap top speaker but with my record embossing needle ,so i will give that a go ,i can hear its a clean sweep well past 10 khz so hope my redesign will record cleaner on the higher frequencies ...report back with Tests in a day or 2
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Re: Mechanical video recorder

Postby Harry Dalek » Sun Oct 20, 2019 4:49 pm

Well on the last record lathe head it works but needs a lot more amplification so its bloody loud on the recording side ,at the higher frequencies it drives my kids crazy :lol: but i can't hear it that's all that counts don't you think ? :roll:
I had another idea today which now seems correct i was recording to slow at 33 rpm not really even good even for SSTV ,pretty much its poor at 45 rpm and at 78 rpm SSTV can be recorded but i have syncing problems now to over come
I can see the picture would be pretty much ok if not for the line sync being so far out some videos below of my experiments .
Using the ipad to air receive the recorded 8 sec slow scan via the record player speakers here
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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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Re: Mechanical video recorder

Postby Viewmaster » Mon Oct 21, 2019 4:58 pm

Harry, if I were you, I would concentrate on getting reliable sync.
Without sync you're sunk !
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Re: Mechanical video recorder

Postby Harry Dalek » Mon Oct 21, 2019 7:43 pm

Viewmaster wrote:Harry, if I were you, I would concentrate on getting reliable sync.
Without sync you're sunk !


Hi Albert
The Slow scan 120 line recording is off frequency not much but yes it sure does need syncing ,i have a problem at 78 rpm that's the top recording speed with the friction on the platter .
It needs a touch more speed i might have to change the pulley wheel on the motor to a larger one ,to go in and out sync either end i need a range for adjustment and i am at the lower end .
I do have a laser focused to a 50 hz strobe disk and a photo transistor picking up the pulses //////because there are 3 encoders for 33 45 and 78 rpm i am just using one of them .the recording pulses from the encoder are giving 103 hz on that 78 rpm recording ..
I tried sync at the lower 33rpm speed which was giving 50hz it was very jerky and the low speed .
My thinking here was is since i am recording to wanted record player speeds i just wanted to sync the platter to this and correct sync would follow if the sync pulse is recording which it is for SSTV .
The other problem is i am not playing back from my recording machine if i did this would be much easier speed would be correct for play back ,i have not bothered yet to make the play back arm again ...
The record player of cause plays it at the correct 78 rpm speed but it was recorded on my lathe a touch slower 76 77 rpm perhaps ...
IF i can play the recording back on my lathe i have speed control this would be useful like my cassette player it has play back speed control spot on for sstv for sstv recording slew the sync to correct speed .
I could also just play it to the p7 analog deep image SSTV it also has line sync adjustments to over come the software monitor narrow line sync adjustment.
So Albert i am looking into it ...i think also for NBTV the recording speed must go up i sort of under stand why you went close to line speed for recording !~
Getting there Albert being able to record SSTV is a little step but a large step above voice and music difficult and satisfying !
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Re: Mechanical video recorder

Postby Harry Dalek » Sun Oct 27, 2019 6:18 pm

I made a play back arm with ceramic pickup and a little audio amp so i can play back the recordings on the record lathe to a speaker and feed the recordings to the laptop for viewing on MMSSTV ..there is of cause drift on play back back with no syncing .
Now i know there are images recorded as suspected i will have to try syncing again so i am listening Albert just taking it slow ...just another step i have to work on ....
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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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Re: Mechanical video recorder

Postby Harry Dalek » Sun Nov 10, 2019 6:26 pm

Sorry have not been on for a while been away on Holiday before i left i started on motor control again .
I built the SSTV demodulator have to still ad the line sync detection which i will use along with a 15 hz clock and 4046 PLL in a standard motor control the mechanical sync in this case is the recovered sync recorded on the record ...well that's the plan so far !

ON something else which i found very interesting an optical amateur video recorder 1957 hats off to him ! wonderful inventing have to be the first optical disc video recorder !
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Re: Mechanical video recorder

Postby Harry Dalek » Fri Nov 15, 2019 11:18 pm

The SSTV record play back system and where i am up to ...

Start off with the ceramic phono cartridge used here...

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The Arm with ceramic phono cartridge on the turnatable

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This is then fed to a BA526 low noise amp ic and used circuit below ..output feed to either loudspeaker or to laptop mic input to sstv software for viewing no syncing of cause if used like this as in last few posts a lot of drift line per line ...

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Now up to seeing if i can improve on the playback as the idea is to use the varying frequency SSTV line sync (16HZ which most of the time its not ) from the record and line it up to a 16 hz clock via a 4046 PLL

I first needed a SSTV demodulator to get the baseband output for line sync detection i used Steve's demodulator the out put from the BA526 circuit is feed to input of this
SSTV Demod V2 1.gif
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Then the demodulated Base band signal is feed to Klass's Line sync circuit both above used in the Deep Image CRT P7 SSTV reason i used both here again they work !

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Output of line sync circuit below on my scope



Now here is where the step... i am not sure about as every thing is a lot slower than what i have we have done in the past same motor control idea but pulses to switch the motor will be a lot slower if i go with the below idea mmmm

Circuit below with sstv line sync from record to 4046 PLL and 4060 clock 16hz clock to 4046 PLL

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I put an LED on the 4046 to see if there is syncing happening as i recall on the NBTV version the light comes on on syncing but here it flashes and slowly syncing flashing starts to slow and stop and the light just stays on when this happens the out put of the 4046 pin 13 pulse starts to die away until i turn off and turn back on the circuit :roll:

Any case i sort of think even if this part works using a 16 hz pulse to switch the motor for motor control the switching pulses are very slow and the gearing on the motor might amplify this effect speculating ?

I did make the clock variable so if syncing is possible multiples of 16 hz 32 64 128 hz so on may be that could be tried ?

So this is where i am up to i have not put in the motor control transistor yet as i am not sure how the 4046 would go yet the thing can be still changed if need be .
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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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Re: Mechanical video recorder

Postby Harry Dalek » Sun Nov 24, 2019 5:46 pm

The route to using both 4046 and bistable idea so far have not got me to far ,i could not get a pulse out of the 4046 perhaps the frequencies i am using are to low for it perhaps ,the bistable adjusting the pulse widths to match looked more promising but have not used it for this so far .

I thought i would split the problem and get some clean motor control via pulse width modulation motor control and worry about the syncing next ...i now have pulse width motor control in my motor control speed range for the record embossing lathe player next is to add the feedback for the record sync pulse to it .

I thought i would try 2 different clocks a 4060 as mentioned before and a 4047 which the 4047 in case the extra trigger reset inputs which might come in handy to try ...the 4060 just has a reset and i also have the 555 monostable really think pin 5 can be used for feed back from the player which i think is the more likely way to go .
Both circuit ideas work well as is ....i built 2 one to test it works and other to have on one board

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3.JPG


So at the moment very good motor speed control but i have yet to connect the record sync pulse to these ideas but having PWM control is a very hopeful ...been taking it slow and trying to think which is the best way to go ..so far i now know what works and what doesn't for this geared motor control !

My thoughts are skipping ahead to my NBTV goal since its pretty much proven the play back cartridge needle can emboss a CD DVD into a record and at the moment i think doing past frequency sweep tests with my stepper motor DIY cartridge it might only be good up to 8 or so khz from memory .
I am thinking about just using a ceramic cartridge since it has the band width as in trying to reverse its function ! a magnetic one would be a lot easier but i don't have one handy at the moment apart from the home made one ...so will not be easy as i would have to pump a bit of amplifier wattage into this thing but at least i know from my work here what should be heard from it to record .
I have also not forgotten all the other problems even if this works but it has been done by others so it is possible ...back to work :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: Mechanical video recorder

Postby Harry Dalek » Sat Nov 30, 2019 4:48 pm

Testing today my results were no better than a direct Dc control of my platter motor if not worse with a framing very sine wave looking , i can still see a movement of the mechanically recorded sync pulse frequency as well .
Below sync pulse from the record recording after processing with steves and Klaas circuits
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Even with the frequency off the sync should just slew one way or the other in a straight line ....thinking about it i have come across this problem before but in NBTV using mechanical sync for a Nipkow camera where the encoder disc had a slight wobble this caused the raster lines to have a similar effect to this sstv record recording ...I ended up just not using the mechanical sync apart from motor control and using a crystal clock and monostable for pulse width adjustment and reinserting a clean sync pulse on the video that worked .

Making this more complex but not using the recorded sync pulse for video processing but reinsert a clean one on the baseband video then remake the FM subcarrier with a voltage controlled oscillator this should if any thing straighten up the video lines even with platter speed a touch off .
My memory i recall making SSTV video for a mechanical scanner and Steve mentioned an improved idea..... below a quick rethink of it for repurposing here .
SSTV may be easier to record but to remake the video does make it harder least i am have way there was not expecting to use the baseband video but looks like it will come in handy .
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Last edited by Harry Dalek on Sun Dec 01, 2019 7:12 am, edited 1 time in total.
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