Mobile Install: Grounding

Discussion in 'Mobile Radio Systems' started by KI4KGR, Jun 9, 2018.

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  1. KI4KGR

    KI4KGR Ham Member QRZ Page

    I'm installing an IC-7000 in my wife's Tahoe for an upcoming road trip. I've seen a lot of install pictures where people run the power and ground to the battery. I spent years installing large car stereo systems and we never ever for any reason did this. The best rule of thumb to prevent engine noise was to make the shortest ground feasible. This was on large 10k+ watt systems with multiple batteries.

    Since I see so many HF mobile stations running power and ground to the battery I got to wondering is there a specific reason for this or is it just they don't know any better? For HF Mobile Radios (I'm only talking about power and not RF) is one method preferred over another assuming a proper power ground?

  2. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Maybe for you, but the truth is elsewhere. The one single thing you do not want to do in a modern vehicle, is create a ground loop.

    The negative lead does not go to the battery. Rather, it goes to the battery ground connection on the chassis, to prevent bypassing the battery monitoring system. Visit my web site if you want more information.
    K6LPM and WA8FOZ like this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Think you got it backwards, stereo guys do not know what they are doing. There are two reasons to wire battery negative directly to the battery.

    1. Noise plain and simple . When you use the chassis of the car, power is mixed with all the other devices like ECM, Ignition, power windows, ext generating noise on the ground plain.
    2. Most vehicles today are uni-body construction and have very poor electrical connection from one part of the body to the next resulting in high voltage loss and adding to the noise problem.

    Any Two-Way radio you buy new today be it Amateur or Commercial have long Positive and Negative battery leads so they can be ran directly to the battery term post. In fact many commercial radios radio chassis is not even bonded to the negative battery supply to mitigate noise problems associated with car vehicle frame and chassis issues. When done that way the only connection to the frame is via the antenna coax where the antenna bonds to the hood or roof to make a noise free ground plane for the receiver.

    Sounds like you car stereo guys are still living in the past when you used the chassis and frame for power.
  4. KI4KGR

    KI4KGR Ham Member QRZ Page

    "Think you got it backwards, stereo guys do not know what they are doing."

    An entire industry has it wrong and you have it right? Interesting.
    AI7PM likes this.
  5. KI4KGR

    KI4KGR Ham Member QRZ Page

    Thanks! Car Audio and HF Radio are two different things where things are done differently. That's a helpful answer (with a helpful site) that gives a reason as to why.
  6. KF5LJW

    KF5LJW Ham Member QRZ Page

    Professional Engineer for 40 years. What are your credentials? Car Stereo installer? You are right about one thing. Car Stereos and Transceivers are different. A Transceiver is far more sensitive to noise.Thus requiring more attention to details.

    Ever try researching to see what the automobile manufactures have to say on the subject?

    Example for FORD.
    Or perhaps GM.

    Read any of them. They all say basically the same thing, directly to the battery. The only other appropriate place for the negative is to locate the cable going from the battery term post to the engine block or firewall and it will be the larger of the cables. cables .

    I gave you the exact reasons why, interference with the car ECM and electrical systems. Dumbed down is Ground Loops.

    If you cannot take the heat, don't dish it out.
    Last edited: Jun 10, 2018
  7. N7WR

    N7WR Subscriber QRZ Page

    They do know better. Car stereos and 2 way radios (of all types) are completely different animals. You may be good at installing stereos but my advice is to listen to the advice of those who have spent their careers in mobile 2 way radio.
  8. KI4KGR

    KI4KGR Ham Member QRZ Page

    That's why I came here to ask. My comments were not meant to create a controversy.
  9. KI4KGR

    KI4KGR Ham Member QRZ Page

    Stop a minute and take a deeeeeeeeeeeep breath. Nothing was meant as a personal attack. I never thought that there were hams that were so sensitive to the topic. I knew that a mention CB Radio create a lot of animosity between the two but I never though Car Stereo was such a touchy subject.
    AI7PM likes this.
  10. K7JEM

    K7JEM Ham Member QRZ Page


    This is from a newer Motorola installation page. Note the negative wire.

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