BoatBanter.com - View Single Post

glen herrmannsfeldt

wrote:

I need to get a VGA signal from the Nav Station in my boat to the
monitor in the bridge. I could just run a VGA cable (about 4m worth)
but I need to pass the cable through some small holes for the looming
(sp?) and the DB15 connectors wont fit unless I make the hole bigger.

I am thinking about running the VGA singal over CAT5e, which a Google
search seems to suggest is possible. I was wondering if anyone had any
better ideas, keeping costs fairly low.

The impedance is different enough that you will get visible reflection
at anywhere close to VGA frequencies. I believe VGA, like most analog
video signals, is 75 ohm coax (unbalanced). Matching that to 100 ohm
balanced line is not easy with passive parts. Using active circuitry
you can generate the balanced signal needed, and convert it back
at the other end. That takes a number of very fast amplifiers
(I think three video, plus two sync, but I am not so sure about sync
signals for VGA.)

I believe the boxes are commercially available, because it is sometimes
the best way to send video long distance. (The cheaper cable makes
up for the added cost of conversion.)

If you find the connectors with separate pins that you solder and
then install it isn't too hard. You still want the appropriate
multiple coax cable, though.

Has anyone here had any success cutting the end off a VGA cable and
wiring on a new DB15 for example?

Finding ready made cables has been easy enough, and finding the
required cable in bulk hard enough, that I haven't tried.

-- glen