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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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17th Nov 2008, 3:21 pm | #1 |
Dekatron
Join Date: Nov 2006
Location: London, UK.
Posts: 3,496
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Understanding the 'intelligence' in a video signal
I want to understand the components of a video signal as prep for tackling my first TV restoration sometime soon. It will be a 60s set, b/w.
I am reasonably au fait with UHF construction methods (I've built a VHF+ converter for tiny signals) antennae, the sound receiver, line output (I isolated one as an EHT+ supply when I was 14) and power supply of a TV, but also have big gaps in my knowledge, especially the video amplifier and frame timebase. I do know how scanning works, however. I know how timebases work in isolation, but not as part of the whole broadcast to picture chain. This is no small 'gap', obviously, when it comes to understanding telly! When I say 'I want to understand', I mean a really thorough explanation that is in terms of waveforms and their components and any relevant timings. If there are any good online resources, that's brilliant. Can I give an example of my level of ignorance? Right now, not having made a study of this, I don't know whether the sync pulses are generated within the receiver or are a component of the signal intelligence through the aerial! I guess they come with the signal. But that's just by way of example. Cheers, experts!
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Al |
17th Nov 2008, 3:32 pm | #2 | |
Retired Dormant Member
Join Date: Dec 2003
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Re: Understanding the 'intelligence' in a video signal
Quote:
Books(all out of print): Amos and Birkinshaw, Television Engineering vols1-4. Hutson: Colour Television Theory Fink: Television Engineering Handbook (various editions) Wharton & Howarth: Principles of Television Reception |
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17th Nov 2008, 3:38 pm | #3 |
Hexode
Join Date: Jul 2004
Location: Paris, France
Posts: 346
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Re: Understanding the 'intelligence' in a video signal
Hello,
interesting reading here: http://www.sptv.demon.co.uk/ If you give me your Mail address, i can send you TV basics documents scanned from Rohde & Schwarz (test gear manufacturer). Namely: - TV Technology (24 pages) - TV Standards (16 pages) *if demand is high, i will post to my PhotoBucket site for others to see. Best Regards jhalphen Paris/France |
17th Nov 2008, 3:42 pm | #4 |
Hexode
Join Date: Aug 2007
Location: Bristol, UK.
Posts: 480
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Re: Understanding the 'intelligence' in a video signal
There are line sync pulses at the beginning of each line (in the horizontal blanking period) and a frame sync sequence at the top of each field (in the vertical blanking period). These pulses are below the black level of the video signal.
From these, you can determine black level, and the vertical and horizontal start of line and field. The two fields each contain half the lines and are interlaced to give the complete picture frame. That's a start anyway ... |
17th Nov 2008, 4:08 pm | #5 | |
Dekatron
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Re: Understanding the 'intelligence' in a video signal
Quote:
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Al |
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17th Nov 2008, 4:10 pm | #6 | |
Dekatron
Join Date: Nov 2006
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Re: Understanding the 'intelligence' in a video signal
Quote:
Thanks for the reading list Jeffrey. I will try to acquire or borrow some of these
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Al |
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17th Nov 2008, 8:32 pm | #7 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Re: Understanding the 'intelligence' in a video signal
Hello,
A good book (covers colour as well) http://books.google.com/books?id=dRG...9HMQ#PPA542,M1 I've not managed to get a paper copy yet though! It's more 625 line but the monochrome info should get you going. Also an excellent page: http://www.penders.cwc.net/otsyncframe.html and another good one here http://graffiti.virgin.net/ljmayes.mal/var/tvsync.htm I have to say, if you've got an oscilloscope then hook it up to a video signal (from a video, DVD, Aurora etc) and get the lines locked you'll see quite a bit. What's broadcast is pretty much that but amplitude modulated for B&W. If you have a 'scope with a z-mod (i.e. brightness) input feed to that too (you may need to amplify a bit), then if you've got a second channel hook up an AF signal generator set it to 25Hz and you've made a telly, not a good one but it'll get you started. A really good place to start I have to say is playing with NBTV where the video is at audio frequencies, it's a lot easier to get circuitry working at these lower frequencies and you can get a full-blown, low resolution CRT monitor going very quickly. I was always "scared" of TV until I started playing and now realise it actually does make sense! PM me is you're interested... Scaling things up to "real" TV is simple, but more fiddly as you need a lot more bandwidth and good behaviour over a large frequency range, but if you're into VHF / UHF stuff you'll know more about that than me... Dom |
17th Nov 2008, 11:14 pm | #8 |
Dekatron
Join Date: Nov 2006
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Re: Understanding the 'intelligence' in a video signal
Hi Dom, and thanks for this and the other bits of advice and links. Excellent stuff and I now have a few leads to follow.
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Al |
21st Nov 2008, 4:48 pm | #9 |
Hexode
Join Date: Jul 2004
Location: Paris, France
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Re: Understanding the 'intelligence' in a video signal
Hello Astral Highway,
Just checking, have you received the R&S data i sent you? Best Regards jhalphen Paris/france |
21st Nov 2008, 5:01 pm | #10 | |
Dekatron
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Re: Understanding the 'intelligence' in a video signal
Quote:
thanks
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Al |
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