Electronics > Projects, Designs, and Technical Stuff

Help with VGA extension cable

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alah:
Hi ALL; I gogled for VGA connections and found some stuff, but I still have doubts and before blowing my very precious portable or Monitor I prefer consulting. I´m attatching a pinout for opinions, it supposed to be the bare minimum connections for it to work; Thanks.

Whales:
There are 1000 ways to blow up a device using a cable.  You need to tell us what you're doing, otherwise we're just guessing.

N.B. the N/C pins are optional, used for things like 'EDID'.   The bare minimum is all grounds, HSYNC, VSYNC and at least one colour channel (although some monitors may be picky and need a certain one or all three).

Whales:
Doh, it's in the title.  Apologies, "extension cable".

Some old CRT monitors might be damageable with bad sync pulses, but I think that's about it.  You probably want to use coax cable of the right impedence for VGA for each of those signals, otherwise you will get a blurry/bad mess on the other end.

I recommend cutting open a shorter VGA cable that you don't care about and having a look inside, see how it's made.

If you don't provide the EDID wires (marked as N/C in your diagram): you will have to manually force a resolution/mode on your computer, as it won't be able to auto-detect the monitor.

How long of an extension do you want to make?  After a certain distance it's really only practical using active (powered) VGA repeaters.

bsudbrink:
I don't know what your length requirement is or what your budget is, but I've had good luck with these:

https://www.ebay.com/itm/VGA-Cat5e-Cat6-Extender-300ft-Video-Repeater-Over-Ethernet-Cable-Up-to-100m/153881643459?hash=item23d40f89c3:m:mKgvrXZBFKzpB_tRnZmpVkQ&var=453930968948

richard.cs:

--- Quote from: bsudbrink on April 01, 2020, 03:51:14 pm ---I don't know what your length requirement is or what your budget is, but I've had good luck with these:

https://www.ebay.com/itm/VGA-Cat5e-Cat6-Extender-300ft-Video-Repeater-Over-Ethernet-Cable-Up-to-100m/153881643459?hash=item23d40f89c3:m:mKgvrXZBFKzpB_tRnZmpVkQ&var=453930968948

--- End quote ---

I've not tried twisted pair VGA extensions, but I remember reading two key things: 1) It works 2) For long lengths the different twist rates between the pairs appear as differing propagation delays and you get poor horizontal alignment between the colours. I suspect that box has a balun per colour, and then does some clever munging with the fourth pair (and perhaps between pairs) to get the sync and audio in.

I'm curious over what length you've tried it and if you saw that effect?

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