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Old 10-14-09, 11:51 AM   #14
bwheaton
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Default Re: Which NVIDIA Graphics Cards can display 2048x2048 ?

Quote:
Originally Posted by JaXXoN View Post
An RGB signal impedance missmatch most typically results in "shadows".
There are ready-to-buy impedance transformers available. Just google for
50:75 impedance transformer.
Just thought I'd flag this: the specification for video is that the driver and receiver present a 75 ohm characteristic impedance. In an input, that can be manipulated with a 'terminator' - a set of 75 ohm resistors essentially.

You should never put a transformer onto video signals, the only minor exception being special 'humbuckers' designed to filter AC frequencies only.

H & V sync have more variations, but are generally less fussy, as long as there's enough signal for the clocks to trigger, and the reflections are small enough to not mistrigger. They aren't always 75 ohm.

If your impedances aren't matched up, you'll see 'ringing' i.e. reflections down the video line. Nothing in video should ever be 50 ohm. At the frequencies you're talking about, everything in the signal line will need to be very short, and specified for this sort of bandwidth. For instance - a 50 ohm cable would probably look really, really bad. Any sort of video distribution would look really bad unless it's specifically for that sort of bandwidth.

Bruce
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