What co-ax to use for s-video?

[zilog jones]

Can I just use a pair of normal co-ax used for UHF/VHF RF for s-video, or does it have to be something specific regarding impedance or whatever?

Problem is I'm using the s-video out from a games console (PlayStation2) which has a non-standard AV socket, so I don't want to waste a good s-video cable on this, nor do I want to waste money on another crappy s-video cable that doesn't use co-ax cables. There isn't much of a selection for PS2 s-video cables in my local shops (as RGB SCART is more common here, and better, but alas, useless for capturing), and anyway it'll be cheaper to make my own ^_^

I've already tried making my own before - I have some spare AV plugs for the PS2 from composite cables, and just soldered the s-video cable on to the appropriate pins - but the picture turned out quite grainy as the s-video cable was cheap crap that used 4 unshielded wires instead of 2 co-ax wires. So surely any old co-ax would be better than that?

[jggimi]

Huh? Coax has only two conductors; its designed for RF signals. S-video (aka Y/C) has a 4-pin DIN connector, since it carries two separate component signals. Coax cable, on the other hand, has an impedence (50-ohm, 75-ohm, etc.) that must be matched to an RF signal. Granted, I'm not sure what the 4-pin cables in S-video actually carry, but its not an RF signal.

[jggimi]

Well, a google search found this: http://www.datapro.net/products/1165.html

Apparently, 75-ohm coax connections may be used for each signal -- luminance and chroma -- since this cable uses exactly that.

[SeeMoreDigital]

I guess it would be possible to run a pair of (2No) 75 ohm RF cables side-by-side. One for the "chroma" signal and the other for the "luma" signal.... But, depending on the diameter of the cable, you might have problems soldering the wires to the s-video connector(s)!

Also, using a solid centre cored cable might introduce some signal loss.


Cheers

[zilog jones]

Yeah, that's what I was planning on doing. Good point about trying to solder them to the mini-DIN plug though... it'll be a challenge!

@jggimi:
*Good* s-video cables use two co-ax cables put into one cable. The 4 pins on an s-video plug are for chroma, luma, and their respective grounds.

Co-ax isn't necessarily used for RF! Never seen BNC cables, I take it? They're co-axial, and are often used used for composite and RGB connections, and even computer networks back in the good ol' days!

[Arachnotron]

There are some nice general articles about video cables here (http://www.bluejeanscable.com/articles/index.htm)

[zilog jones]

Thanks for the info there. I was considering using some co-ax originally used for short-wave or CB radio or something (some sort of radio), but after reading that it seems likely that won't be 75 ohms.