Is it possible to run my VGA monitor through an RS232 cable?

[Gameshow Host]

I'm buying an extension cable bundle which will extend my monitor, keyboard and mouse into another room (long story why).

The cable bundle includes an RS232 cable, which I'd like to use for my monitor. However, my monitor has the old VGA port on the back.

Can I just buy adapters (such as this) for both ends and hook it up? Will this work? Will it degrade the picture quality at all? Are there any specs I should look for in an adapter?

[zing269]

Adapters should work. I'd be more concerned about the distance. VGA is an analog signal so it will weaken with distance. The quality of the cable, wire gauge, and shielding all matter. The resolution of the signal also makes a difference with higher resolutions needing shorter cables.

[Skiller]

A RS232 cable is not nearly as well shielded as a good VGA cable would be. Certainly an issue with longer cable lenghts. And with VGA, anything longer than 2 meters (6 foot) should be considered long, unless you run low resolutions only. Also every junction point, such as that adapter cable, deteriorates the signal further.

Ideally you want a thick (and I mean thick) VGA cable which is as short as possible and without any adapters.

[Cornucopia]

VGA cable uses 15pins, and usually, ALL 15 are needed.
Rs232 serial cable uses 9pins. You will be missing 6pins, so even if you find a way to modify connectors to adapt, you will not have a complete signal.

Scott

[pandy]

How do you know if this is RTS232 cable or perhaps cable for KVM that looks like RS232 DB9 cable but it is not...
Technically there is no problem to carry VGA signals over 90 meter of Cat 5 Twisted Pair cable so everything depends what type of cable you have, RS232 doesn't require twisted pair cables but cheap KVM's may use connectors and cables in non standard way and how they look may be misleading.

Amazon is full of VGA to Cat 5 converters https://www.amazon.com/vga-cat5-adapter/s?k=vga+to+cat5+adapter some of them are passive (not recommended) and those more expensive are active (they should work). Generally cheap, passive equipment with long cables is not a good idea.

[Gameshow Host]

Thanks so much for the answers guys!

We have a difference of opinion:

Adapters should work.

You will be missing 6pins, so even if you find a way to modify connectors to adapt, you will not have a complete signal.

Who's more right?

As for the cable length, that's not an issue because the KVM extension I'm buying is optical and can send the signal 20 kilometers! (Like I said, it's a long story!)

[pandy]

We have a difference of opinion:

Adapters should work.

You will be missing 6pins, so even if you find a way to modify connectors to adapt, you will not have a complete signal.

Who's more right?

VGA require R,G,B signals and H, V (can be combined) so 4 wires (4 pairs) is enough to carry VGA signal - R,G,B are wide bandwidth type signals when H,V are relatively similar to RS232.
To carry wide bandwidth signal probably passive converter - balun (transformer) is used - such baluns are designed to deal with twisted pair cables. as 9 pin D sub connector can carry 4 pairs then if your cable is fully wired there is small chance that it will work. But your "serial" cable need to be fully wired (sometimes there are only 2 wires in serial cables as XOn/Xoff protocol is commonly used) and not crossed (so can't be so called Null Modem type - if i recall correctly RS232 terminology you need DTE DCE cable).

So everything depends on cable.

[zing269]

Early VGA cards and monitors often used 9-pin connectors, the addition pins on a 15-pin connector are used to send EDID / DDC data.

The adapter you linked to should work as long as you use the same adapters on both ends and the KVM cable is fully wired straight through.

Like pandy said

So everything depends on cable.

[Gameshow Host]

Thanks so much Pandy, Zing, and everyone! You guys are geniuses! I'm going to give it a shot and hope for the best.