What's A Drain Wire?

[Kiggsia]

I installed a Raymarine Element fishfinder last week. The power cable, in addition to the red & black battery wires, has a gray wire called a drain wire intended to be hooked up to a common RF ground point. Would this be the metal chassis of my stereo radio/cassette player which is insulated from the aluminum hull of the boat? Yet the directions say that if there is no common RF ground point the drain wire should be connected to the negative battgery terminal wire. Should I hook the gray drain wire to the stereo chassis though?

 

[GA_Boater]

I would connect the shield wire to the negative post of the battery. The purpose is to help minimize electrical noise.

 

[sam am I]

The drain wire (seen here as un-insultated wire ran between foil and shield)is a un-insulated wire that is woven into AND is electrically common with a cable's over wrapping inner foil and outer shield.....Typically, it is electrically tied to the return on the signal source side and is left floating at the destination.

Consider power as the source when working with just a plain power cable, e.g., tie drain wire to return at power source side then just float shield and drain wire at destination side.

 

[Kiggsia]

The drain wire (seen here as un-insultated wire ran between foil and shield)is a un-insulated wire that is woven into AND is electrically common with a cable's over wrapping inner foil and outer shield.....Typically, it is electrically tied to the return on the signal source side and is left floating at the destination.

Consider power as the source when working with just a plain power cable, e.g., tie drain wire to return at power source side then just float shield and drain wire at destination side.

Thanks for definitive reply here. I'm thinking that 75 ohm coax is similiar, where the return line is woven shielding around the power wire, grounding out any rf interference from the unit through the power wire?

 

[sam am I]

Thanks for definitive reply here. I'm thinking that 75 ohm coax is similar, where the return line is woven shielding around the power wire, grounding out any rf interference from the unit through the power wire?

Very much so yes, AND it also prevents outward radiation of it's own signal.