Frequency Multiplication using LT1256, Input signal is NTSC composite video - Page 1
Forum section: electronics / projects

author: Kashif khan
author_rank: Contributor
timestamp: January 08, 2022, 05:18:23 pm
content: Hi thereLT1256fa.pdf(386.6 kB - downloaded 89 times.),I am designing a circuit that will take an NTSC composite video signal so that I can multiply the input frequency from X1-X32 and also can control the phase of the output signal.For this purpose the IC which I think so far suits best for the project is LT1256 (datasheet attached), there are some application circuits included in the datasheet but I can't figure out so far how to implement the frequency multiplication from this IC.please suggest me a good approach towards the circuit design.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 08, 2022, 05:54:40 pm
content: Which part of the composite signal do you want to multiply? So many component frequencies from the time base and colour burst, let alone the video content.Composite may have a bandwith of >=6MHz. 32x6MHz is 192MHz. The LT1256 has a BW of 40MHz. So You might need an RF mixer.What are you trying to achieve?

author: Kashif khan
author_rank: Contributor
timestamp: January 08, 2022, 06:26:01 pm
content: The attached images will clear you out what exactly I need.

author: Benta
author_rank: Super Contributor
timestamp: January 08, 2022, 07:35:29 pm
content: No, it's not clear at all what you need.The LT1256 is a video amplifier and will not do frequency multiplication.And as @Terry Bites asks, what do you want to frequency multiply?Horizontal sync?Vertical sync?Colour subcarrier?

author: Kashif khan
author_rank: Contributor
timestamp: January 08, 2022, 07:39:09 pm
content: The datasheet states in the application that it can be used as a multiplier /modulator/video fader. Basically i want post-editing on composite video signal in real-time and display it on CRT.

author: Deni
author_rank: Regular Contributor
timestamp: January 08, 2022, 07:44:51 pm
content: Yes, it can multiply AMPLITUDE, not frequency...

author: Bud
author_rank: Super Contributor
timestamp: January 08, 2022, 07:45:56 pm
content: The only multiplying you've done so far is posting same topic in multuple subforums.

author: SiliconWizard
author_rank: Super Contributor
timestamp: January 08, 2022, 08:14:37 pm
content: Quote from: Bud on January 08, 2022, 07:45:56 pm

author: Terry Bites
author_rank: Super Contributor
timestamp: January 09, 2022, 08:22:29 pm
content: That unit in your photo is part of an analog synthesiser. Why not mention that from the get go? Where does NTSC composite video come into it? Do you want to alter TV audio?Lucky for you, I am a mind reader:So it seems to me that you need a very basic synth module input CV input gain control etc, and analog multiplier an hp/lp/bp filter block to get the desired harmonics and an all pass filter to control phase.LT1251 is a VCA of sorts, a 2 quadrant multiplier not the 4 quadrant multiplier you need. Maybe an SA602A if you're on a tight budget.

author: CaptDon
author_rank: Super Contributor
timestamp: January 10, 2022, 02:21:32 am
content: What good is a 'multiplied' video signal?Do you mean multiply (A.K.A. amplify) the amplitude of the signal. You sure as hell don't do post editing with a multiplier. Sounds like you don't know what exactly you want to do or what the proper terms of what you want to do is called. Multiplying any part of an NTSC video signal would make it just about useless as the rest of the signal chain wouldn't know what to do with a now non-NTSC signal. Spin the idea wheel again and get back to us, maybe on just one forum also.

author: SilverSolder
author_rank: Super Contributor
timestamp: January 10, 2022, 03:33:49 am
content: The problem with frequency shifting a video signal is that you would also be shifting the frame rate and the line scan rate... which you don't really want to do in your final result.So the processing of the signal is more complicated than just a frequency shift. Then there's the problem of synchronizing the channels that go into making the new collage of smaller pictures... they all have to be in sync, or it won't work.

author: Terry Bites
author_rank: Super Contributor
timestamp: January 10, 2022, 03:19:31 pm
content: I'm thinking this project is probably a load of BS. Or maybe an atempt at a video synthesiser.How about you give us a block diagram of your secret DARPA projet?

author: Bud
author_rank: Super Contributor
timestamp: January 10, 2022, 04:31:11 pm
content: OP is using wrong terminology. This seems to be what he is afterhttps://community.lzxindustries.net/t/all-about-staircase/1342Additional information is attached.This module is a part of a video processing system though, so some control signals may be not part of the module and supplied through the system connectors , e.g. the system clock and/or horizontal/vertical sync.

author: CaptDon
author_rank: Super Contributor
timestamp: January 10, 2022, 05:30:54 pm
content: O.K., after watching the video this all makes more sense. This is a part of a complete system which maintains the H and V syncing while producing 'special effects'. It is much more apparent now what you are trying to do. So now it comes down to, are you trying to build one of these modules rather than buying it? It would appear the module is only one functional block of a totally integrated system. The staircase module seems that it can't really stand alone without the backplane and other interactive signals. I wonder how the video monitor and system output was in sync with the external NTSC signal? Was there a sync recovery included in one of the modules to sync the processing system to the external NTSC input?? Or was the entire studio/system connected to a master GenLock? Would this system accept to old 'Random Interlaced' camera video signals? The effects are nice if you have a need for them but it mostly looks like a visual toy for wacky weed smokers.

author: Bud
author_rank: Super Contributor
timestamp: January 10, 2022, 05:52:03 pm
content: Quote from: CaptDon on January 10, 2022, 05:30:54 pm

author: Terry Bites
author_rank: Super Contributor
timestamp: January 10, 2022, 09:42:32 pm
content: I'm on Acid and I'm getting all kinds of video effects.

author: Kashif khan
author_rank: Contributor
timestamp: January 10, 2022, 11:14:58 pm
content: I think this videowill be enough to understand what I need.

author: SilverSolder
author_rank: Super Contributor
timestamp: January 11, 2022, 12:05:54 am
content: That looks pretty cool!I guess you'd need some circuitry to (re)create stable sync pulses, and then "mess" with the video part of the signal depending on the input?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 11, 2022, 04:38:49 am
content: So... you want to reinvent the Scanimate?

author: Kashif khan
author_rank: Contributor
timestamp: January 11, 2022, 09:50:32 pm
content: yup exactly!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 12, 2022, 02:38:34 am
content: Good luck.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 12, 2022, 04:55:27 am
content: I just remembered:https://worldradiohistory.com/Archive-Radio-Electronics/80s/1987/Radio-Electronics-1987-09.pdfMight give some building blocks.Part IIhttps://archive.org/details/radio_electronics_1987-10