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Car charger radio interference?

Discussion in 'Android Devices' started by rcflyer620, Jan 5, 2010.

  1. rcflyer620

    rcflyer620 Lurker
    Thread Starter

    I saw a similar thread but it didn't address this problem...
    When I use a car charger with my Eris, as soon as I plug the phone in it steps all over my FM radio reception. WiFi, BT are both off.
    I tried a different charger with the same result.
    Any thoughts?

  2. Podivin

    Podivin Android Expert

    1) If your car has more than one power outlet ('cigarette lighter', in my day) try using a different one to see if it's the same result.

    2) The way you phrased the problem, it sounds as though it only happens when the charger is plugged into the phone - as opposed to any time the charger is plugged in, whether or not the phone is connected. If that's true try charging the phone while the phone is off (off, not just asleep). This will help to determine if the interference is coming from the phone or the charger.

    3) You mentioned that WiFi and BT are both off, might try turning off 3g also, just for fun. (sure, it'll be fun :) )

    4) Try it in a different car, tuned to the same radio station, to see if the problem happens there.

    5) (and my personal favorite) Check the ground wire on the radio, especially if this is an aftermarket radio. A radio will WORK once the antenna lead is plugged it because that's a ground. However RF interference can be a problem unless there is a properly connected ground wire.
  3. OfTheDamned

    OfTheDamned The Friendly Undead

    It sounds like a ground loop. Pretty much what mhotovec was saying in #5.

    You will need to run a new ground wire for the radio and/or the power outlet.
  4. erisuser1

    erisuser1 Android Expert

    If the answer to mhotovec's step #2 is "yes, it only is a problem when the Eris is charging with the phone turned on", one way to mitigate the problem is with one of those snap-on ferrite chokes on the charger cable at the end closest to the Eris. (That's the little lump on your laptop's charger cable near the plug for the PC). Snap-on types can be found through specialty electronics distributors, but be advised that they are designed to suppress EMI in various frequency ranges - if you can find one that is designed for FM suppression, so much the better.

    Another way might be to simply move the charger to a different plug to get the charger cable a little bit away from the radio - if your vehicle has back-seat charger plugs, give that a try (if it is convenient). This would work only if the interference is "over the air", so to speak.

    There are lots of ways that RF can interfere - direct radiation is one way, but conduction along power mains is another, and it is possible that the charger plug and radio are on the same fuse circuit in the vehicle. This is along the lines of #5 in mhotovec's suggestions. In-line or choke-style ferrite filters on the radio's power supply line are another possibility - or even moving the radio to a different circuit. (Depends on exact details of your car's wiring harness).

    Probably you are in for a little experimentation to narrow down to a solution - let us know what you find out. (Also, it might be a good idea to post which charger cable you are using - the Verizon car charger?)

  5. xmancool2

    xmancool2 Lurker

    This problem happens when using low quality Chinese chargers that don't have proper rf isolation, so the electric noise produced by the charger (of course) is bounced back to the car's electrical system.

    Buy an original car charger and you will see the difference.

HTC Droid Eris Forum

The HTC Droid Eris release date was November 2009. Features and Specs include a 3.2" inch screen, 5MP camera, 288GB RAM, MSM7600 processor, and 1300mAh battery.

November 2009
Release Date

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