Static on AM when charging phone in 300M

Discussion in 'Chrysler 300' started by PAul Newman, Aug 30, 2003.

  1. PAul Newman

    PAul Newman Guest

    Hi,

    I recently got a 2000 300M to replace my previous 2000 300M. With this
    car, I get a lot of static on AM whenever I use my cigarette lighter
    to charge my phone. It happens on stron and weak stations and makes it
    impossible to listen to AM while using the charger. This never
    happenned on my other 300M and the dealer says they have no idea how
    to fix it.

    Any ideas?

    Thanks

    Paul
     
    PAul Newman, Aug 30, 2003
    #1
  2. PAul Newman

    MikeHunt Guest

    I would suspect a loose connection in the lighter wiring.
    I'm curious, why another 2000, why not upgrade?


    mike hunt
     
    MikeHunt, Aug 30, 2003
    #2
  3. PAul Newman

    PAul Newman Guest

    Mike,

    My original 300 was a lease. I liked it a lot and had low miles on it.
    Took great care of it. Unfortunately, the buyout on the lease was way
    higher than what I could get the car for on a lot with the same or
    less miles. I got my current 300 for $3k less than the lease buyout
    and it had 4k miles less on it. Chrysler financial really blew when it
    came to customer service and satisfaction. I got another 2000 because
    of the steep depreciation of the car. It didn't seem to pay to
    upgrade.

    Paul
     
    PAul Newman, Aug 31, 2003
    #3
  4. You might be able to wire a 300 pf capacitor between the + side of the
    cigarette lighter and ground to fix this. Just go to a ham radio store and
    tell them your story, they have had plenty of experience helping people to
    get noise in their car supressed. If this doesen't fix it, the problem is
    most
    likely noise radiating from the charger and cord. You can test this by
    getting
    some aluminum foil and grounding it then wrapping the charger and cord
    and phone up in it while they are on, and seeing if the noise goes away.

    Ted
     
    Ted Mittelstaedt, Aug 31, 2003
    #4
  5. PAul Newman

    PAul Newman Guest

    Thanks for the reply Ted. This car is still under warranty. Isn't this
    something they should be able to determine and repair? Like I said
    previously, this is the same charger I used in my last 300M and I
    didn't have any problem.

    Thanks

    Paul
     
    PAul Newman, Aug 31, 2003
    #5
  6. PAul Newman

    Bill Putney Guest

    Choke = inductor = choke.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, Aug 31, 2003
    #6
  7. To be honest they can't. The problem is that the charger is putting out
    RF that has harmonics directly in the AM band. It is like you set up
    a bunch of mini am radio stations in your car all transmitting at once.
    Since the RF from the charger is more powerful than the RF from the
    regular AM radio stations, it is basically erasing the proper AM signals
    in it's vicinity.

    The charger is quite obviously the problem. It should be shielded and
    it isn't. You can write a complaint letter to the FCC and copy the
    charger manufacturer, under US law, they are mandated to mitigate
    the interference. Of course, if they don't, and the FCC declines to get
    involved, you have no recourse except a civil suit. In most of these
    cases the FCC does not get involved unless they receive many hundreds
    of complaints about a particular item.
    This actually points more to radiated RF from the charger instead of RF
    leaking back through the + power connection. Unfortunately this is more
    common of an interference problem. Your last 300M may have had for
    example a steel frame in the dashboard, the new 300M perhaps has plastic.
    It could also be that the antenna lead from the AM radio is of a poorer
    quality
    than the old car, or perhaps the antenna design is different, or maybe you
    have
    a bad ground from the antenna to the car frame.

    Whatever it is, though, the law requires that all radio transmitters have
    FCC approval,
    and operate in an assigned band. As long as your charger is generating RF
    it is a
    transmitter, thus it falls under FCC jurisdiction, and clearly it has no
    assigned
    radio band. Thus it is illegal. While the older 300M may have had a better
    body structure/antenna positioning/whatever that made it less suceptible to
    the
    charger's interference, it's not Chrysler's problem, really, because the
    charger
    isn't supposed to be broadcasting anything.

    Now, if your 300M's AM radio is getting interfered with by a bunch of OTHER
    stuff out on the road, that's a different story. Then you can get on
    Chrysler's neck.

    Ted
     
    Ted Mittelstaedt, Sep 1, 2003
    #7
  8. PAul Newman

    Steve Stone Guest

    I thought I read someplace that the 300M uses a RF preamp to boost the
    signal to the radio received from the antenna in the rear window ?

    The charger noise might suggest a problem in this RF preamp or its
    connections and wiring or wiring to the antenna ?

    Has the rear window ever been replaced on this car ?

    Steve
     
    Steve Stone, Sep 1, 2003
    #8
  9. PAul Newman

    Bill Putney Guest

    Not likely to happen. The FCC regs are written very cleverly to allow
    them to excuse themselves from any involvement unless they *really*
    *really* want to be involved (i.e., if it is a problem of very wide
    spread public awareness and it becomes politically expedient for them to
    get involved).

    The *emissions* part of their regs. say that any device emitting r.f.
    energy can't ineterfere with proper operation of other devices. The
    *susceptibility* part of their regs. say that any receiving device must
    not be affected by devices emitting r.f. So when they receive
    complaints, historically, and citing the regs., they simply tell the two
    manufacturers that they have a problem (since clearly, both violate the
    regs.) and they stay uninvolved.

    As you point out below, this also may very well be a "conducted
    emissions" (interference transmitted thru the wires of the vehicle, r.f.
    ground loops, etc.) problem rather than "radiated emissions" (sent thru
    the air to the antenna of the radio) problem.
    No - many devices legally emit r.f. energy without being classified as a
    transmitter and assigned a radio band. Microwave ovens, our computers,
    ultrasonic medical devices, etc. The regs. simply define amplitude
    limits for any given frequency (via a specified curve that varies in
    amplitude over the defined range of frequencies). The fact that the
    device emits some r.f. does not classify it as a radio transmitter in
    need of an assigned band for intentionally transmitting a signal like a
    radio station. That pretty much gets enforced in that samples of the
    production devices (or pre-preproduction samples) are taken to certified
    antenna ranges where they are tested over the specified bands of
    frequencies and tweaked until they pass. Future production devices must
    incorporate all the changes that it took to achieve the passing of the
    tests.

    Once that is done, it is assumed that the future production devices meet
    the spec. (and that's a big assumption because repeatability between
    samples as far as r.f. emissions behavior is not always very high -
    we're talking very low levels that can literally get changed an order of
    magnitude by routing a single conductor differently on a p.c. board, or
    grounding a capacitor at a different point on the same ground plane)
    unless there is a big (think high visibility and politically expedient)
    reason to think otherwise - and simply receiving a (or several)
    complaint(s) from the field is not enough to cause the FCC to jump into
    action.

    Unless the FCC has good reason to believe that something changed between
    the antenna range qualification and the present production devices, they
    are easily able to blame both devices without arbitrating if there is a
    complaint of interference. They do this by simply citing the catchall
    "thou shalt not interfere with other devices" and "thou shalt not be
    susecptible to emissions of other devices" rules. They don't have the
    budget to do otherwise even though technically they should. They mostly
    are involved with the qualification of the device and subsequent
    approval. After that, once in production, all bets are off, barring, as
    I said before, that it would be politically expedient for them to fix a
    high visibility real world problem. (You can imagine the politics that
    can occur if they try to force a large company to spend a lot of money
    on recalls and/or fixing a problem for future production if the product
    is not in the public limelight.)
    Like the stepper motors at the car wash that I drive by every day
    interfering with my a.m. radio reception. It would be a waste of my
    time to contact the FCC about that.

    BTW - Chrysler radios are known by auto manufacturing insiders to
    historically be the worst in the industry (Norht American anyway) for
    noise rejection.

    Bill Putney
    (to reply by e-mail, replace the last letter of the alphabet in my
    address with "x")
     
    Bill Putney, Sep 1, 2003
    #9
  10. I merely mentioned the FCC in order to show how useless it would be.
    They aren't going to waste their time with a $15 cell phone charger.
    However keep in mind with AM that noise rejection is very difficult. Most
    electrical noise is AM (ie: varying amplitude) rather than a carrier shift
    such
    as in FM or other modes of radio transmission. So even with the best AM
    receivers out there your still going to get interference if the transmitter
    is
    strong enough. It's why AM has been relegated to talk radio, these days
    mostly occupied by conservative fringe elements. (Is that why you listen
    to AM Bill? ;-) Maybe the FCC bureaucrats figure the more interference
    the better! :) :)

    Really the best option if he doesen't want to buy another charger is to try
    working with some shielding or add in a cap to the + line. I hope he posts
    a followup, it would be interesting to see what the problem was.

    Ted
     
    Ted Mittelstaedt, Sep 4, 2003
    #10
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