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Mobile Radio Install DC Power Myths

Discussion in 'Mobile Radio Systems' started by KF5LJW, Sep 12, 2019.

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  1. KX4O

    KX4O Ham Member QRZ Page

    Can we assume insurance might not cover this?
    NH7RO likes this.
  2. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    And yet, we have thousand of members here, a great many who have mobile installations, and in the last 11 years, I cannot remember a single thread about their radio burning up their car!
    K7JEM likes this.
  3. KX4O

    KX4O Ham Member QRZ Page

    Key to this scenario is the failure (or partial failure) of the grounding point where the battery ties to the chassis. This is rare, but, sure enough, it happened to my 2005 Pacifica so it can happen.
    KA0HCP likes this.
  4. KF5LJW

    KF5LJW Ham Member QRZ Page

    It is called Ironic Humor. The humor is in the truth, if you cannot figure it out real quick, you probable need to find another hobby that does not involve electricity.
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    Well sir that is the Safety Issue, and doing so comes with risk.

    If that is not enough to convince you and others ask yourself this? Why would you want to noise up your radio by improper power connections. When you put your cable directly to the battery creates a Mother of a Ground Loop. Your radios negative wire and coax as conducting and passing automobile current through your radio. Just think what that does. You have foreign currents running through your radio add voltage drop with the extra current going through your negative. If you were to measure the current in positive and negative are going to see a difference. Something like 1/4 amp on positive in RX, and 3 amps on negative. That voltage drop is felt at the radios Signal Reference and you can measure it. DC alone you can see with a volt mete connected chassis to negative buss inside your radio. That is Common Mode Noise. Now think of all the circuits in your car flowing through your radio. Those are not static loads. Most are digital capable of generating RFI.

    Talk about voiding vehicle warranties if there was a problem. Manufactures are very specific with auxiliary equipment power connections. Consult them and you get best practice.
  6. KX4O

    KX4O Ham Member QRZ Page

    Do you really not understand I share your view on this topic?
  7. KF5LJW

    KF5LJW Ham Member QRZ Page


    Just because you have been doing it wrong and endangering yourself for years does not make it OK. Kind of like saying I smoked 2-pack of cigarettes for 20 years and am just fine.

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