I have spliced/extended/shortened numerous radar cables
. They actually can be cut and connected through a terminal block without any noticable change in performance. The main issue is a setting - Sweep Timing, that must account for the "travel time" of the video signal through the cable. Many units, esp. older ones, will require a service
manual to find the adjustment inside, and it has to be checked/adjusted on a sea trial. Some older Furuno
units have the adjustment accessible from the front panel, under a little cover. New Furunos have the adjustment in the installation
To check sweep timing, you must take the boat out and position in front of a long straight target, like a commercial
warf, bulkhead, bridge, etc. Correct sweep timing will display a straight line, incorrect setting will display a line either dipped or peaked at the center. Incorrect sweep timing will cause targets to be displayed at incorrect distances.
The above does not apply if your scanner (dome) is digital (it will have a very small cable). You should be able to extend the cable a reasonable distance with no troubles.
I also have some extra cable, for Furuno.
I need about 5 feet of Furuno cable with 10 wires and one looks to be a coax. Any help there?