I thought the whole steel band was the antenna?

Discussion in 'iPhone' started by Mjmar, Jun 25, 2010.

  1. Mjmar macrumors 65816

    Joined:
    May 20, 2008
    #1
    The iPhone 4 antenna confuses me. If the whole band acts as the antenna then why do the calls drop only when you hold the phone in the bottom left corner? And how do radio waves travel through steel anyway? I wanna know so I can hold the phone the right way without loosing service.
     
  2. quagmire macrumors 603

    quagmire

    Joined:
    Apr 19, 2004
    #2
    The issue is bridging between the two antennas. The steel band below the left hand seam is the cell antenna. Above it is the WiFi/BT/GPS antenna. The rubber seam is to keep those antennas separate. When your finger/hand touches both in that area, it creates a bridge causing what I would imagine some kind of interference or if it is software related, tricking the software to think the signal is crap.

    That is what I have observed in videos and my own tests. Touching the rubber seam itself does nothing to my signal nor does just touching the cell antenna part below the seam.
     
  3. saving107 macrumors 603

    saving107

    Joined:
    Oct 14, 2007
    Location:
    San Jose, Ca
    #3
    quagmire is correct, and their is a more in-dept article I saw earlier today that explains what's going on, I'll see if I could find. Also, because of radiation testing, the FCC requires that all phone manufacturers place the Radios on the lower portion of every phone (keep it further away from the brain), so this is not just an iPhone issue.

    [​IMG]

    [​IMG]
     
  4. Mjmar thread starter macrumors 65816

    Joined:
    May 20, 2008
    #4
    So the iPhone 4's antenna IS the steel band, whereas the older iPhones antennas were not visible?
     
  5. quagmire macrumors 603

    quagmire

    Joined:
    Apr 19, 2004
    #5
    Correct. The iPhone 3G and 3GS had them under the plastic backing and the original under the black strip at the bottom.
     
  6. Mjmar thread starter macrumors 65816

    Joined:
    May 20, 2008
    #6
    IDK about you but that seems unsafe to me.
     
  7. Setter Guy macrumors newbie

    Joined:
    Apr 2, 2010
    #7
    Agreed. File the iPhone 4 with horseless carriages, dirigibles, and microwave ovens.
     
  8. Errk! macrumors 6502

    Joined:
    Mar 6, 2006
    #8
    Great explanation - thanks. I was confused too.

    If this is the case, shouldn't we be having the same problems if you hold it so that, say, your thumb is on the left side and your other fingers on the right? Does it only matter if one finger is touching both sides at one time? And if so, why would that be?
     
  9. Gigamaster89 macrumors member

    Joined:
    Oct 1, 2008
    #9
    If for whatever reason you decide to put your hand on the top where the bands connect, you would have the same problem?
     
  10. quagmire macrumors 603

    quagmire

    Joined:
    Apr 19, 2004
    #10
    Frankly, I have no idea why that is the case. Touching the two separate bands on the opposite side vs joining them by that seam. I am no engineer, so I am far from an expert on this. But, this would be my best guess( out of the blue, etc). As we all know and has been pointed out, how can stainless steel be the antenna while at the same time, it disturbs the signals( why the original iPhone and iPad 3G has that black strip). What I think Apple engineers did was take that physics and used it for their advantage. Where the whole outer band absorbs the signals and some how directs them to the main antennas.

    And as pointed out in step 12 of iFixit's iPhone 4 teardown, the cell antenna at least( they never pointed out the WiFi/GPS/BT antenna) is where the left seam is. So the interference is the strongest there causing the issue. Where touching it on the opposite sides doesn't cause much of an issue because you're not near the actual antenna.

    Thinking of this guess, maybe it isn't a bridging problem. It's just you're blocking the actual antenna from getting the signal. This could explain why the problem still happens even with WiFi/BT/GPS all turned off. Again, I have no idea how Apple engineered the iPhone and antenna system nor am I an engineer at all myself. So I can very well be 100% wrong.

    I tried that and it doesn't affect WiFi or cell reception. Even when I am far away from the router( using the theory of the issue is only present when the signal isn't that great).
     
  11. Uabcar macrumors 6502

    Joined:
    Aug 31, 2009
    #11
    So the hand bridging the two antennas issue makes perfect sense- and explains why using a case seems to resolve the problem.

    What does not make sense is the argument that other phones have the same problem. I don't see how this could be an issue with the 3gs for example. No metal to 'short out'. I'm sure the added mass of your hand - to transmit though- would impact the signal to some minor degree on all phones.
     
  12. Amnesia87 macrumors 6502

    Joined:
    Jun 19, 2010
    #12
    The reason it doesn't cause nearly as big a problem when in your right hand is while yes your hand is technically still bridging the signal. We are very bad conductors, lots of resistance, so when it's the palm of your hand it much easier for the signal to hop that 2-3mm to get from one antenna to another, going across your entire hand is a much smaller issue, most of the signal is lost to resistance.
     
  13. quagmire macrumors 603

    quagmire

    Joined:
    Apr 19, 2004
    #13
    That is why I put the following in my above post.

    And as that states, I could very well be 100% wrong since I am no engineer.


    That makes sense....
     
  14. saving107 macrumors 603

    saving107

    Joined:
    Oct 14, 2007
    Location:
    San Jose, Ca
    #14
    here is the article I spoke of.
    http://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-antennas.html

    here are some highlights from the article, but its worth reading the whole thing:

     

Share This Page