Three Composite along Cat-5

Information on this page may be out of date or apply to old equipment. Use with caution.

Joe Wharfe says: "I see no reason why we would still need this, and I've never heard of anyone using this, but to my untrained mind it sounds cursed. Good riddance." If you have reason to believe this isn't something that ended up in the Bin Pile, feel free to remove this tag.

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.

Michael.Cullen 22:59, 11 January 2010 (UTC) Not wanting to turn this into a conversation, I think that the difference is that one has a male VGA on the other has female. You can actually connect them together and run a video signal through it. The upside of this is that if there are any other differences, the connectors prevent this from causing problems. Woodstock suffered bad cat5 runs - it worked over a short cable (well, one of the BNCs did...)

Technical Operation

Rextron part number EVA214, consists of a transmitter (part no. EVA12L, serial number V37034HG00065) and receiver (part no. EVA02R, serial number V35034HG00065) which are linked using any convenient CAT-5 network cable. You can then put a VGA video signal plus mono audio into the transmitter, and get them back out of the receiver. Also has built-in DAs at both ends, so each box has two independent outputs, as well as the CAT-5 output from the transmitter.

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.