Three Composite along Cat-5

Practical Setup

This is a way to get three composite video signals in the same direction between two points over a single CAT5 computer network cable. It also has the optional function of sending mono audio in the same direction as the video signals over the sam cat 5 cable.

This requires a length of CAT5 computer network cable long enough to join the points you want to send video between, the pair of VGA over CAT5 adaptors, and the pair of BNC to VGA break-out boxes. The cat5 adapters are both different, IE there is a 'transmitter' and a 'receiver'. Both of these are powered from a mains-to-DC adapter.

From the old YSTV website: "Both the BNC to VGA adaptors and the VGA over CAT5 are different at the two ends, so you need the right bits at each end of the cable."

Malcolm.chambers 20:57, 1 January 2010 (UTC) The powered cat5 adapters are certainly different and the right one must be at each end. HOWEVER, I don't see why the bodged BNC to VGA adapters should be different, surely the same pin is used at both ends of a VGA cable for each colour. Having made the claim that they're identical, problems (IE none of the three video signals reaching their destination) were experienced at Woodstock 2009, and if the BNC to VGA bodges are indeed different then this could be the source of the problem.

Technical Operation

This was an inspired confection first developed to overcome a lack of long video cables at Woodstock 2007, but offering some very nice advantages for the future. The starting point was the availability of the pair of boxes for sending VGA analogue PC video over a CAT5 network cable. These commercial adaptors provide a neat, practical solution to the impedance matching and balancing required to send the component video and sync signals of a standard VGA signal over the 110R twisted pairs of CAT5 cable.

Because the Red, Green and Blue components of the VGA picture are sent as separate signals in the VGA connector, each on a 75R coax cable, it is possible to send over the same circuits three lots of composite video signals independently. Whilst for a given resolution the colour components have lower bandwidth than a composite signal, the much higher refresh rate and resolution of PC video means that there is plenty of bandwidth to carry a standard composite signal.

The boxes already provide the necessary HF correction for making up the losses in long runs of cable, switched to accommodate variable cable lengths, giving good picture quality.