Wiring help

John Bitting

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Wiring up a Kenwood race radio and PCI intercom. Do I need to go direct to the battery with both powers or can I run one power into the cab into a distribution block? Thank you
 

Zambo

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I run a wire from the battery switch in the cab to a noise filter and from there to both radio and intercom...seems to work fine like that.
 
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Battery power is best, draw when transmitting will reveal any weak connections.
 

green787

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Wiring up a Kenwood race radio and PCI intercom. Do I need to go direct to the battery with both powers or can I run one power into the cab into a distribution block? Thank you
I think it's a complete myth that you have to run either to the battery.... As long as the wire that feeds the distribution block is large enough, then I don't see any advantage.... I run everything right off the fuse block succesfully with zero noise....
Just float (do no connnect) the black ground wire from the intercom.... This will prevent a ground loop that picks up alternator noise....
 

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racer_dude

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I think it's a complete myth that you have to run either to the battery.... As long as the wire that feeds the distribution block is large enough, then I don't see any advantage.... I run everything right off the fuse block succesfully with zero noise....
Just float (do no connnect) the black ground wire from the intercom.... This will prevent a ground loop that picks up alternator noise....

You are half right.


You only do not ground a COM6 intercom from PCI (old gray metal box intercom).

COM-X, 4 link pro etc etc all need to be grounded together with radio to rid system of any ground loops and noise that can be created.

The reason we (past tense for me) say to wire directly to battery is two sided.

1) To eliminate chances of noise from alternator or ground loops
2) In the event of a roll or other incident, if a driver or co-driver turns the both switch off, there may be a need for intercom communication between the two to check for safety reasons still
 

green787

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You are half right.


You only do not ground a COM6 intercom from PCI (old gray metal box intercom).

COM-X, 4 link pro etc etc all need to be grounded together with radio to rid system of any ground loops and noise that can be created.

The reason we (past tense for me) say to wire directly to battery is two sided.

1) To eliminate chances of noise from alternator or ground loops
2) In the event of a roll or other incident, if a driver or co-driver turns the both switch off, there may be a need for intercom communication between the two to check for safety reasons still
Oh... Ok, on the COM6....
I still want everything off when I shut off the master battery switch.... Otherwise it's really not a "master" switch if you have bypassed items....
Broadcasting on the radio could cause a fire if there was a gas leak in the right place... Evacuate the car first.... Then re-approach to see if you can use the radio safely....
 

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shrive81

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can you explain the ground loop interference and best practice to avoid it for all race and offroad wire applications
 

green787

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can you explain the ground loop interference and best practice to avoid it for all race and offroad wire applications
I was told to lift the black wire on the intercom to isolate the ground... Only need one ground and that's the radio...
 

dzrt performance

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since the question has been asked "what is a ground loop" i will try and answer in simple terms. the first thing to remember is electricity ALWAYS TAKES THE PATH OF LEAST RESISTANCE.

think of it this way....for a circuit to "flow" electricity, you need a connection to a positive AND negative source. in this case that being the battery. While it is common practice to take the negative side of the battery to the vehicle chassis and then any device to the vehicle chassis as well, the vehicle chassis is commonly thought of as "ground" but this is not really accurate. The chassis is being used as a conductor to get back to the negative side of the battery and not a true source of negative voltage.

Herein is where the problem lies. since the chassis is really a conductor and not ground...you will here a term thrown around called "ground potential". what this means is how much resistance is between your ground point on the chassis and the battery negative terminal. You can measure/test this by taking a meter reading in ohms, one probe on the negative side of the battery and one at the point on the chassis you wish to ground your device.

what you will find is that at there is some resistance at various ground connections across the vehicle. this is what forms your ground loop. deices that have more resistance on the ground side compared to other are ultimately the culprit.

in other words, the interconnecting wires between devices will flow current between them on the negative side of the circuit since their grounds are at different potentials (resistances). this is why floating a ground wire or changing ground locations will eliminate, reduce or greatly intensify the buzz you hear from a ground loop.

this is why single point ground system are recommended when wiring a car. "best practice" says take the ground wire for all your devices to a single common point to eliminate ground loop possibilities.

You may also find that a working electrical system will have problems like this pop up down the road. as moisture, dirt stress from vibration, heat, chemicals, etc inevitably work their way into connections, resistance builds up and "gremlins" appear on an otherwise function electrical system. I see many many well prepared and maintained cars that the electrical system is completely neglected, thinking it will last for ever. that simply isn't the case.
 
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