Connect VGA card to monitor with BNC connectors

The following figure shows the connection diagram which you can use to make adpater cable to connect your VGA card (or other computers with 15 pin VGA style connector) to monitors with BNC connectors. BNC connectors are used in high resolution monitors, because BNC connectors have better high frequency characteristics than normal 15 pin VGA connector.

The monitors suitable for use with VGA cards have 5 BNC connectors and they have the following fuctions:

Signal   Function        Color in cable
R        Red             Red
G        Green           Green
B        Blue            Blue
H/HV     Hsync(+Vsync)   Black
V        Vsync           White or Gray

The picture below is drawn based on wiring of the cable suggested to be used with Nokia 21" monitors. The wiring is not exactly the same that was in that wiring diagram. I made a new version of the picture based on more reliable information sources. Note that the wire grounds monitor ID pins 4, 11 and 12 to make the VGA card to detect that there is color monitor installed.

Cable wiring diagram

If you are making your own VGA to BNC cables then you must use correct and high quality components to guarantee good picture quality. All the cableing should be done from 75 ohm micro coaxial cable and the BNC connectors must be 75 ohm impedance models.