I am rewiring my 74 cd 28-boy did it need it-several years ago I installed a Furono 1720 radar-now I noticed the power cord from the unit is actually a sheilded cable-I spliced in about 5' of duplex wire and ran it to the panel-it has seemingly worked perfectly with out the sheilded cable-question-what will happen if I do not use sheilded cable? and if I do where or to what do I ground the outside braided cable to? negative ground to the battery? ground to the engine? (which is the same thing-or can I ignore it-I don not get any interference with the radar on and the engine running-fyi-I went through 200' of 10 gauge duplex re-wiring this boat-I note the originial wires were twisted around each other I assume to prevent the creation of a magnetic field once current was put through them-how come we don't see twisted cable anymore?-thanks
grenier@ma.ultranet.com
sheilded radar power cord
Moderator: Jim Walsh
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Larry deMers
Re: sheilded radar power cord
With most radars, the transmitter is in the dome section, and the display is the controller head. The signals between the two are generally DC signals or slow pulses, so these can be just single color coded wires in a cable, but the higher frequency signal, which is the screen data usually is sent through a piece of coax that is in the same wiring harness as the single color coded wires.
While you don't want noise being picked up by or radiated by the wiring from the radar, -and this is the reason for the shield, which is usually tied to the battery negative terminal (preferred over the engine block as a ground, as that is one connector removed from the battery, making it an inferior ground by comparison), your wire extension must not have noise riding on it or it does not come near a noise source that can be induced into the wires.
Why is Twisted Pair not seen much anymore? It's less expensive to run parallel pairs than taking those parallel pairs and twisting them in a drill. Better? no. Noisier? you bet they can be.
If you are rewiring, twist them with about 5 twist per inch for 12 AWG marineized wire, and 3-4 twists per inch for 10AWG pretinned wire.
Good Luck!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing Lake Superior~~~
demers@sgi.com
While you don't want noise being picked up by or radiated by the wiring from the radar, -and this is the reason for the shield, which is usually tied to the battery negative terminal (preferred over the engine block as a ground, as that is one connector removed from the battery, making it an inferior ground by comparison), your wire extension must not have noise riding on it or it does not come near a noise source that can be induced into the wires.
Why is Twisted Pair not seen much anymore? It's less expensive to run parallel pairs than taking those parallel pairs and twisting them in a drill. Better? no. Noisier? you bet they can be.
If you are rewiring, twist them with about 5 twist per inch for 12 AWG marineized wire, and 3-4 twists per inch for 10AWG pretinned wire.
Good Luck!
Larry DeMers
s/v DeLaMer
Cape Dory 30 ~~~Sailing Lake Superior~~~
Wayne Grenier wrote: I am rewiring my 74 cd 28-boy did it need it-several years ago I installed a Furono 1720 radar-now I noticed the power cord from the unit is actually a sheilded cable-I spliced in about 5' of duplex wire and ran it to the panel-it has seemingly worked perfectly with out the sheilded cable-question-what will happen if I do not use sheilded cable? and if I do where or to what do I ground the outside braided cable to? negative ground to the battery? ground to the engine? (which is the same thing-or can I ignore it-I don not get any interference with the radar on and the engine running-fyi-I went through 200' of 10 gauge duplex re-wiring this boat-I note the originial wires were twisted around each other I assume to prevent the creation of a magnetic field once current was put through them-how come we don't see twisted cable anymore?-thanks
demers@sgi.com