iPhone 4 Antennas are electrically connected. Implications?

Discussion in 'iPhone' started by spblat, Jul 14, 2010.

  1. spblat macrumors 6502a

    spblat

    Joined:
    Jun 18, 2010
    #1
    That is very weird and I haven't seen this observation elsewhere. I got the same result. 0.3 ohms or less across all three antenna portions, which is no different from the reading I get when I put both probes on the same antenna segment. If the steel band wasn't an antenna I'd expect it to be ground. I'm no RF engineer, but it doesn't make sense to me for those three segments to be electrically connected to each other.

    Any engineering types have anything to contribute to this? Has this already been discussed?
     
  2. tominabox1 macrumors regular

    Joined:
    Dec 18, 2008
    #2
    RF does not equal DC - many types of antennas have a DC connection like this (the details are..well technical) At RF frequencies (you know, the ones where cell networks operate) those "shorts" become less "short" and more "open." Without getting into the technical stuff I think that answers your question.

    (for a more detailed example...take an inductor, its DC resistance is basically zero, but it will become highly "resistive" at a high frequency, which is inverse to a capacitor which has a DC resistance which is very high and an RF resistance that is very low...get it?)
     
  3. spblat thread starter macrumors 6502a

    spblat

    Joined:
    Jun 18, 2010
    #3
    Got it. End of story. Non issue. Thanks.
     
  4. mgamber macrumors 6502a

    mgamber

    Joined:
    Jun 12, 2008
    Location:
    1966
    #4
    To take it just a bit further (because I'm a geek), the reason is called "skin effect". As frequency increases, power is contained to the "skin" of the conductor. At cellphone frequencies, it only uses a outermost couple of nanometers of the conductor. If the gap is at least that deep, it looks like an open circuit to the transmitter while looking like a closed circuit using a multimeter's DC source.

    Skin effect is also why sticking your fingers in a 50/60 hz wall socket may well kill you while grabbing a microwave antenna will likely just burn the hell out of you. The lower frequency goes through you and may stop your heart while the very high frequency never goes deeper than a few nanometers of your body.
     
  5. malnar macrumors 6502a

    malnar

    Joined:
    Aug 20, 2008
    #5
    Two antennas.

    [​IMG]
     

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