Recording NBTV on cassette tape.

Forum for discussion of electronic television. Generally, stuff to do with CRTs and not using mechanical displays.

Recording NBTV on cassette tape.

Postby Monochrome » Sun Jan 14, 2018 1:22 am

Hi Folks,

Its been a very long time since I posted on this forum due to the usual distractions of work, grandchildren etc but my interest in NBTV is still as keen as it was 35 years ago and I try and keep up-to-date via posts here and via the newsletter.

Anyway, browsing youtube for nbtv related matterial I stumbled upon this video entitled "128 line television on audio tape 3" and while the quality is not exceptional the method used to record the video seemed quite interesting.

If I understand correctly he recorded the video at 2 times normal speed onto a cassette tape and to circumvent the LF and DC offset issues he inverted the video of every other line. I have to admit I have not fully contemplated all the implications of doing this but it does seem a novel approach to the problem of recording NBTV signals and looks like an interesting alternative to using sub-carriers. The only complication would seem to be the synchronisation of the line switching to ensure the line phase is correct on replay.

I wonder, has anyone tried something similar and if so what sort of results did you get? Comments, thoughts?

Here is the video link and if you fast forward 50 seconds into the video we have a Star-Trek clip which is easy to recognise and evaluate...

https://www.youtube.com/watch?v=1kwWmaLkLVk

73,s and happy 2018 to all.

Monochrome (Des M0AYF)
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Re: Recording NBTV on cassette tape.

Postby Harry Dalek » Sun Jan 14, 2018 6:58 pm

HI Des
i think i recall this video ,he has another i will put up if i can find it .
He used some software bit beyond me but it seemed to worked ,Gary has a 120 line 3 colour Frame sequential colour in he's video2NBTV v3 software and we now also have FreeNBTV thanks to smeezekitty which i have been using to make 128 line 12.5 hz video wav files , it can make a variety of line and frame rates very handy to play around with .
viewtopic.php?f=8&t=2458
I will give 128 line and such on tape a go in time but with all my wants of doing this and related projects it all comes down to i need a monitor to view it on in the first place so every thing is on hold till this is going ..i had been using Doms 64 line viewer to view the 128 line video as i can see at least its working showing 2 images side by side as in picture below .
The CRT monitor i am working on i just got my saw tooth oscillators that will drive my crt deflection circuits to sync to 128 line video well the line rate so far so at least that will be in sync .
But yes its interesting seeing how far you can push it on tape BTW the old 87 PXL-2000 could record video on audio tape but it did run the tape a touch faster than normal tape recorders ..don't recall them being sold in my country we missed out on that one .
http://www.labguysworld.com/FisherPrice_PXL-2000.htm


youtu.be/HlX_A1qc3dI

youtu.be/LfmY-t-C5Ow

youtu.be/5LRUAsLqQ

youtu.be/0tAIPH4O48g
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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: Recording NBTV on cassette tape.

Postby Monochrome » Sun Jan 14, 2018 10:18 pm

Hi Harry,

Thanks for the reply and also for the additional youtube links, it seems kargaroc386 had been quite busy experimenting with recording video on cassette.

Re the PXL2000, I have one here though I have only ever fired it up briefly. The drive belts had perished due to old age and need replacement but otherwise its fully functional and just waiting for me to fit the new belts. I dont think the PXL was ever released here in the UK but a few turn up on ebay from people who brought them back from the USA which is how mine turned-up. I really must get around to restoring full operation of the PXL.

I got the PXL hoping it would help me understand how they managed to record the video signal and FM sub-carrier to cassete tape so well and more than anything I wanted to see what was "special" about the heads and tape transport mechanism. In my own 32 line NBTV cassette recording experiments I ran the tape at 10 times normal speed (about 20 ips) and used an FM sub-carrier but I could only get it to work with very small deviation (NBFM) with noisy results though the video response was quite good.

Thanks for pointing me to the new generation NBTV software which looks exciting, I have downloaded the most recent package and look forward to trying it out. BTW your new CRT monitor, does it use electrostatic or magnetic deflection? Just curious.

Thanks again Harry.

73,s

Des.
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Re: Recording NBTV on cassette tape.

Postby Harry Dalek » Mon Jan 15, 2018 10:57 pm

Monochrome wrote:Hi Harry,

Thanks for the reply and also for the additional youtube links, it seems kargaroc386 had been quite busy experimenting with recording video on cassette.


Yes he also did a bit of 64 line as well but as with 128 used he's own software /

Re the PXL2000, I have one here though I have only ever fired it up briefly. The drive belts had perished due to old age and need replacement but otherwise its fully functional and just waiting for me to fit the new belts. I dont think the PXL was ever released here in the UK but a few turn up on ebay from people who brought them back from the USA which is how mine turned-up. I really must get around to restoring full operation of the PXL.


Reading the labguy's report on these even a broken one is still very collectible ,yes you should get it going its an interesting little gadget ..not many things video camera wise go up in price with time .

I got the PXL hoping it would help me understand how they managed to record the video signal and FM sub-carrier to cassete tape so well and more than anything I wanted to see what was "special" about the heads and tape transport mechanism. In my own 32 line NBTV cassette recording experiments I ran the tape at 10 times normal speed (about 20 ips) and used an FM sub-carrier but I could only get it to work with very small deviation (NBFM) with noisy results though the video response was quite good.

I like your idea on the 10 times speed for recording play back that should of given you more bandwidth ,i would of like to have seen it in action !
In the early 90s i used to record noaa and meteor weather satellites on audio tape . The signal is an analog signal consisting of an amplitude-modulated 2400-Hz subcarrier frequency modulating the RF carrier.
Now due to trying to record this unassisted to tape the frequency changes so play back its way off sync ,i used a Pll to fix this on play back to pc ,i still have the gadget it used to also lock on the the 2400hz signal and switch the recorder on and switch it off when the satellite signal was out of range ..
I would think NBTV would have syncing problems as well on audio tape that 400hz sync would be off frequency around a bit depending on how well the play back speed is kept perhaps another way would be control of the motor speed with a Pll .
It all depends on the quality of the machine ,a vcr used as a sound recorder should work its already made for correct motor speed control .
BTW i read also the PXl used a high quality type of audio tape which helped with the band width ...

Thanks for pointing me to the new generation NBTV software which looks exciting,


Yes its very useful you could make your own system if you liked ..the big problem with this is playback unless you use some thing that is standard in the NBTV viewers out there you have to make a monitor ,a scope tv would be easiest ,i wanted to make my own monitor but .viewtopic.php?f=15&t=2481&hilit=scope+tv



I have downloaded the most recent package and look forward to trying it out. BTW your new CRT monitor, does it use electrostatic or magnetic deflection? Just curious.

Thanks again

73,s

Des.


It will just do photos i think ? if so i should try a animated gif and see if i can cheat but yes its easy when you know read my posts in that link to the software as you have to press the default and set format buttons before hitting the start button but once you work that out its easy and you will start changing the other settings.

The monitor idea started out as a electrostatic (The devil A for Andrew) that seems to work fine to 64 line ...and it has sent me on a road project journey as you see in this construction diary !
viewforum.php?f=31

Reading Steve Anderson's advice when he tried 72 line that these small crts can't have a fine enough raster spot for higher line rates so i scrapped 625 line small magnetic crt i have called (The Thylacine) and i am reverse engineering the CRT for a higher line NBTV rates or at least 128 line ...it is also a journey ! it stated out to just be a view finder for the PMT camera so i didn't have to sync it it would be a slave to the camera you will see in the construction diary ....
Now i want to make it also a stand alone medium definition tv monitor and perhaps the higher standards depending on if i have the skills to do that ..so far only displayed very out of sync 32 line as a quick test,i have constructed circuits to sync it now should do 64 and 128 line ...
viewtopic.php?f=10&t=2432
viewtopic.php?f=15&t=2436
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: Recording NBTV on cassette tape.

Postby Monochrome » Wed Jan 17, 2018 4:07 am

Hi again Harry,

Thankyou for the feedback and comment.

I can see I could quite easily get "hooked" again on NBTV, just reading and looking at your posts about the multi-standards monitor stirred my interest. It looks as though you have magnetic deflection pretty well tamed. Up in my loft I have a couple of brand new old stock flat screen monochrome CRT's complete with deflections coils but they had been intended for compter monitors and may not be well suited to grey scale signals.

I like your idea on the 10 times speed for recording play back that should of given you more bandwidth ,i would of like to have seen it in action !


The 10 times speed modification turned out to be very easy, I used an existing deck from an old music system and simply replaced the motor/pully/drive-belt for larger versions. The only thing you had to remember was NOT to use the rewwind buttons :-) The 10x speed should have given me plenty of BW but in practice the standard stereo record/play head I used seemed to be the limiting factor. I think the head gap was ok but the heads struggled at higher than normal frequencies perhaps due to self inductance being to high? If I was to repeat the excercise today I would set-up a tape loop and try a number of different heads from things like old h/disk drives etc which have much lower self inductance.

BTW I gave the two softwares you directed me to a quick try but sadly I was unable to get them working. I tested them on a laptop with 2 GHz processor and 8 Gig RAM running Win7. FreeNBTV opened 3 windows, one of which seemed to be dedicated to the very long list of errors to numerous to mention. Doms software looks more promissing and simply reported that in needed the "dot-net" framework installing in order to run so I may try that one again on another machine with dot-net pre-installed. Sadly my spare time is limited at the moment but (fingers firmly crossed) retirement looms in just a few years so perhaps I can devote more time to this fascinting hobby.

Keep up the good work and good luck with your monitor project.
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Re: Recording NBTV on cassette tape.

Postby Harry Dalek » Wed Jan 17, 2018 9:00 pm

Monochrome wrote:Hi again Harry,

Thankyou for the feedback and comment.


No problems Des

I can see I could quite easily get "hooked" again on NBTV


It is addictive and good to exercise the brain... obsolete processor up there so i have to work it harder :|


, just reading and looking at your posts about the multi-standards monitor stirred my interest It looks as though you have magnetic deflection pretty well tamed.


Its doing well considering it can handle down to 32 lines ,i am using the same deflection circuit as in my SSTV Deep Image but not the sawtooth oscillators ,using a different idea .
viewforum.php?f=19

I am using the opamp part of the circuit and a variation of the 555 here idea here in this video below ,seems to work well but i am yet to hook it up to the monoitors deflection amplifiers just been working on syncing them to the sync pulse at the moment
https://www.youtube.com/watch?v=bVahBmsvirE&t=424s
Up in my loft I have a couple of brand new old stock flat screen monochrome CRT's complete with deflections coils but they had been intended for compter monitors and may not be well suited to grey scale signals.


One of those things never know unless you try i would think yes ,they should of been able to adjust the brightness to them ....i know you can just use them at one level as they may of been made for but should be able to modulate the thing..
I have a larger old scrapped teletype monitor from a 70s machine i was thinking about using one day as well like picture below .

The 10 times speed modification turned out to be very easy, I used an existing deck from an old music system and simply replaced the motor/pully/drive-belt for larger versions. The only thing you had to remember was NOT to use the rewwind buttons :-) The 10x speed should have given me plenty of BW but in practice the standard stereo record/play head I used seemed to be the limiting factor. I think the head gap was ok but the heads struggled at higher than normal frequencies perhaps due to self inductance being to high? If I was to repeat the excercise today I would set-up a tape loop and try a number of different heads from things like old h/disk drives etc which have much lower self inductance.


If that was the problem may be 10 X was a bit much for for that audio head ,its a pity you couldn't adjust this speed and crack it up from normal speed to high top limit .
Would of made a good construction diary on this forum !

BTW I gave the two softwares you directed me to a quick try but sadly I was unable to get them working. I tested them on a laptop with 2 GHz processor and 8 Gig RAM running Win7. FreeNBTV opened 3 windows, one of which seemed to be dedicated to the very long list of errors to numerous to mention.


OH you have the original that needed some add ons if you look again he has posted a fixed version you will have no problems with that ...sorry i forgot to mention the first up load had errors ...try with the latest upload page 2 and download freenbtv alpha v2 ...no problems with that one .

Doms software looks more promissing and simply reported that in needed the "dot-net" framework installing in order to run so I may try that one again on another machine with dot-net pre-installed. Sadly my spare time is limited at the moment but (fingers firmly crossed) retirement looms in just a few years so perhaps I can devote more time to this fascinting hobby.


Yes i use Dom's as well only because Gary's has 60 line in that format ...i need doubles of line rates at the moment 32 64 128 256 so on ..so try them all they all work and have there use's i like them all .
You can always tinker when you have time but understand life does get in the way of hobbies ! :roll:

Keep up the good work and good luck with your monitor project.


Thanks yes i will i want to see my PMT camera on the higher line rages and make a vidicon camera both will need it ..
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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: Recording NBTV on cassette tape.

Postby smeezekitty » Mon Jan 22, 2018 7:16 am

It will just do photos i think ? if so i should try a animated gif and see if i can cheat but yes its easy when you know read my posts in that link to the software as you have to press the default and set format buttons before hitting the start button but once you work that out its easy and you will start changing the other settings.


That was only true for the first version. It now incorporates FFMPEG and can load videos and animated GIFs and play them back. There is currently no sound and a couple of other bugs I'm trying to hunt down though (like screen tearing with certain frame rate combinations, occasional crashes). But overall, it's functional with videos.
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Re: Recording NBTV on cassette tape.

Postby Harry Dalek » Mon Jan 22, 2018 8:58 pm

smeezekitty wrote:
That was only true for the first version. It now incorporates FFMPEG and can load videos and animated GIFs and play them back. There is currently no sound and a couple of other bugs I'm trying to hunt down though (like screen tearing with certain frame rate combinations, occasional crashes). But overall, it's functional with videos.



OH i will give it a go i had not got that far with it as you see i have been testing getting the best quality out of the settings at the moment ...
Great toy for me btw ~! :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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