S-video cabling and noise

[g4bbh]

I have a number of items that can be conected as either composite PAL or s-video (Y/C). I have been progressively changing from composite to Y/C using the usual 4 pin minidin connectors. The items include monitor, TBC, Panasonic WD-MX12 mixer, colour bar generator, cameras (ex CCTV and a 3 ccd camcorder) etc. and I only use composite on the final feed to the transmitter.

Quality is now much better than composite throughout but I find I am plagued with noise a bit like RF interference even when there is no RF around and all switch mode supplies are disconnected. The interference manifests itself as two bands of noise across the picture. Ground bonding all items together and running each cable through several turns on a big ferrite block reduce the noise to an acceptable level. The noise was never present on composite video.

I'm wondering if this is a common problem with s-video. Perhaps the twin 75 ohm coax cores used in the normal s-video cables are inadequate and should have an overall screen.

Sorry - can't afford to go SDI..............

Dick
G4BBH