sokolov%media-lab.media.mit.edu@eddie.mit.edu (Michael Sokolov) (01/14/89)
A number of people have asked me for a summary of the answers to my query about extending keyboard and monitor cables. Many people responded. It seems that good results have been acheived with little or no attention to cable quality at lengths of up to 40 feet for the video, and longer (perhaps 80 feet) for the keyboard. Keyboard: No one has reported any difficulty with extending the keyboard cable, although the limiting factor would seem to be power lossage, which could be alleviated by using low-gauge (large diameter) cable. In case you want to build your own, the pins used are 1,2,3,5,7, and 10. These are all connected straight through, i.e. 1 - 1, 2 - 2, etc. Color Monitor (video): The longest run reported was by Frank Knizek of General Electric, who reports that with "low dispersion RG62A/U, Belden # 9269," he was able to extend a color monitor 80 feet. Keep in mind that all four cables need to be the same length. Monochrome Monitor: Again the prize goes to Frank Knizek. I forward his suggestions: It is built up from four lengths of high quality RG59/U coax. We used Belden number 9266 which has a foam dielectric. The four lengths have D9 connectors at each end (it's a squeeze getting 4 cables into that connector). You need 1 female and 1 male connector. The conductors of the coax connect pin 1 to pin 1, pin 3 to pin 3, pin 4 to pin 4, pin 6 to pin 6. The shields of the 4 cables are combined at both ends and go to pins 7 and 8. The shield is not connected to the shells of the D9 connectors. The monochrome monitor needs 4 cables (wires) because one is the vertical sync, one is horizontal sync and two are used for the video. Pins 1 and 6 are used as a pair for video signal and return of video signal. When we tried to use the cable shield as the return for the video we got terrible echos. For 100 feet you may want to use Belden 9269, an air gap coax, to keep dispersion down. Happy Cabling - Mike Sokolov