no you won't melt things
yes video signal could leak across to audio lines in the snake
yes the video could get ordinary over 20m of audio cable

audio cable is not designed to carry signal at this frequency but will function to a degree
the longer the distance the more the cable will become deaf
if you get my meaning

20m of video cable with BNC connectors at each end ... add two RCA adapters

A broadcast video guy would have a peice of Belden 1505 to throw at you
... or some old analog

think cheap Kev

some RG6 TV coax cable with F connectors and RCA adapters would probably work fine
you may have a peice of old antenae cable (RG6) in the back shed

composite will require one cable
component will require three
S-video isn't so easy only because it would require some trickery with a soldering iron ... unless you buy a 20m S-video cable with connectors
but then that's not zero budget

Well this is more to save running an extra cable. Means I just need 2 speakers + the snake, instead of a VGA cable as well (we'd use component instead) which was always, wherever we went, stretched with about 6 inches of play on it.
All in all there'd be 2m of cable, 20-25m of snake and another 3-10m of (video) cable after that. 3 for normal usage, 10m one time.

I think we'll need to get a 20m VGA cable anyway.
We always use a computer screen to give the band their words, but the congregation's projector has a component in (and a VGA out...hmm)

So I'll assume it would work but with a far from great signal. I'll try it one time, using some long chain of adapters. If that works acceptably, I'll make a cable up. S-Video to XLR, that's a new one.
Thanks anyway.

Edit:
Coax as in aerial lead => we have stacks of that. I just want to run less cables, which is why I wouldn't mind using an unused bit of the snake to do the job, we only use 2/4 returns and say, 12/16 sends so there's space to spare, and for the panto this year, 1 return + 7 sends are likely. Just figured it works out easier and cheaper to use some adapters and existing cable than go buy 20m of VGA lead.

Yellow with red and white:
Yellow is Composite Video
Red and white is left and right audio.

now you have jumped to VGA ??

" Coax as in aerial lead " ... yes RF coax (radio frequency)
but coax is also most video cables including digital 1505
a centre conductor with a shield around it
keeping the distance between centre and shield and the dialectric uniform is all part of the magic of the high frequency cables ... and the low capacitance

that's what makes them different from the average RCA to RCA cable

makes for good SPDF cables too

trouble with video and digital down an audio snake is the signal shape
often has a squarness to it and that will leak into the other lines

IF less cable is the go
AND your snake cable is good quality with excellent shielding per pair
AND
a uniform twist
with differential drivers and inputs (good interference rejection)

then it all might just work
VGA over cat5 will work with the right terminal equipment
... throw it down a few pairs of a snake

try it

I'd love to hear weather this worked or not. I do cable for a living (TV/phone/internet) and I have my doubts. Here is a good artical about component cable. [[url=http://[/URL]="http://www.audiohol…"]Link[/]="http://www.audiohol…"]Link[/]

Well not yet. A VGA would be better quality but defeats my aim of having less wires.
Same with running an RF lead: it defeats the "less-cables" scenario, although probably works out cheaper since it's damn easy to get. Except that the laptop doesn't have an RF out and the adapating is a hassle.

The snake is very likely not shielded, is probably of very low quality compared to pro snakes and I would doubt if it would handle the job without degrading. So I'll probably just say to the minister "we need 20m of VGA before we do any more concerts" or I might not and that gets the laptop off my desk and onto the stage attached to a very short VGA lead, and someone else can worry about it.

This was more of a "lets see if I can save some cash" than anything serious. I might try it next Sunday, if I do I'll get back to you.

Thanks guys.

much more expensive
use a mirowave link to send a composite video signal to the projector

or over WiFi ... 802 wireless

http://sewelldirect.com/Wireless-VGA-Extender.asp

it's less cables
:)

Not sure this helps, but I use 100' S-video cable quite often for remotes with little loss if any. In studio I use a snake from "Markertek" that has DC pwr and BNC and is very flexable.