Bugs, GSM Interference

Discussion in 'iOS Blog Discussion' started by MacRumors, Jul 11, 2007.

  1. MacRumors macrumors bot


    Apr 12, 2001

    The iPhone is an awesome device and will no doubt be a trendsetter for future devices similar to the way the iPod defined the way portable music should be. However, some iPhone owners have been discovering the cost of being on the bleeding edge of technology.

    Currently, there are various bugs plaguing the iPhone's software. These bugs range from minor, application-specific bugs to somewhat major application crashes. We are currently hosting a thread for bug reports, in addition to an entire forum for tips, help, and troubleshooting. If you feel you have identified a bug that has not already been identified as confirmed, let us know (we'll pass it on to Apple once its confirmed as a bug).

    In a non-bug related issue that potential purchasers should be aware of, with the iPhone being a GSM device, it can create interference with audio systems, speaker phones, and some CRT televisions. I have experienced this issue with my iPhone and my car audio system and with my computer's Harmon-Kardon SoundSticks. For more on this issue, continue reading (same issue, different phone).

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  2. loudestnoise macrumors 6502


    May 31, 2005
    Nashville, TN
    GSM interference is pretty much accepted by anyone who uses a GSM phone. Not saying I like it, but it's strange of you to write about this being a "bug." It seems that unfortunately that's just the way GSM networks work.
  3. longofest Editor emeritus


    Jul 10, 2003
    Falls Church, VA
    Didn't say it was a bug. Thought that was pretty clear in the post, but maybe it wasn't. It's a side affect of being a GSM phone, but a side affect that I know I wasn't expecting, and I'm sure a lot of potential purchasers would like to know about, especially if they are switching from Verizon or another non-GSM carrier.
  4. Nicky G macrumors 6502a

    Nicky G

    Mar 24, 2002
    Baltimore & NYC
    GSM noise

    Yep, I experience this both with the mini stereo I plug my iPhone into in my bedroom (infrequently) and in my Acura over its factory Bose sound system (fairly frequently, maybe a few seconds once or twice every 45 mins. or so.)

    At first I thought it was a hardware issue w/ iPhone but quickly remembered the concept of GSM noise when I visited a client of mine whose Treo caused his computer audio monitors to bug out. Not a super big issue, but kind of a PITA.

    For me, it tends to manifest as 2-3 seconds of buzzing/clicking, and then it stops. I would be very curious:

    • If putting it into Airplane Mode stops this behavior (I would think so, and intend to test it out)

    • If this ever occurs with headphones, particularly the factory earbuds (I haven't logged enough time with them to notice)
  5. mcoyne macrumors member

    Sep 15, 2005
    Durham, NC
    I have to agree with the first commenter. Definitely should not have been lumped in to a "bug" post. I'm not sure why you weren't expecting it. Audio interference is a well known problem with all GSM phones. I'm not sure there is anything Apple could do about the problem either way.

  6. benspratling macrumors 6502

    Jan 16, 2006
    GSM noise is a bug, but in the devices it shows up in, not the phones

    Any conductor is an antenna for electromagnetic radiation, of any frequency, they just work on some frequencies better than others. This means that circuit traces on circuit boards and wires inside electrical devices are antennas, and they will pick up radio signals, across the spectrum. Some of the radio signals have data rates that are too fast for the human ear to hear, though, so we don't notice them. The GSM network apparently has some data rates in the audible range, so we notice the noise.

    There is in fact a bug if you're hearing the noise, but it's in the equipment in which you hear the noise, not the equipment producing the noise. Manufacturers of audio electronics should be aware of these facts, and they must include a "Farraday Cage" around their circuits. Items like the Belkin iTrip, my Volvo's sound system head unit, and 3rd party stand up speakers are just three examples of poorly designed audio electronics that do not have a Farraday Cage, because, well, they tend to be heavy, and industrial designers don't know much about electrical engineering.

    A Farraday Cage is an electrically conducting "cage" with holes no larger than half the minimum wavelength you wish to block. A MacBook Pro is a good example of electroincs with a Farraday cage, as are most computers - since they have a metal enclosure. Airplanes are another example of a Farraday cage, though the windows tend to let through most higher frequency signals.

    I could tell you stories of building Farraday cages when I worked in a physics lab to prevent radio signals from interferring with power controlling integrated circuits, but I'll just put it in this off-hand comment instead.

    It's sad that in this day of the proliferation of radio and audio devices that the industrial designers of so many products have absolutely no idea how to make them compatible. Again, there is a bug, but it's in the hardware design of the devices in which you hear the noise, not the phone.

    (Another off hand comment, you can solve this problem in some cases by wrapping aluminum foil completely around the devices that need protection, but since it's so thin, it genenrally also needs to be connected to electrical ground. This is similar to the way the earbuds are protected, by a grounded, conducting shield around the signal wires. You can buy special shielded cables from audio professionals, but they tend to be much more expensive. Plain "speaker wire" at Radio Shack is a great example of unshielded cable that will let in noise if the signal is powerful enough.)

    (Farraday cages work by becoming antennas themselves. They intercept the radio signals before the signals can get inside.)
  7. PBG4 Dude macrumors 68020

    PBG4 Dude

    Jul 6, 2007
    I've run into this noise issue as well when docking my iPhone at work and connecting to my harman/kardon speaker setup. Airplane mode does stop the interference, but now I cannot receive calls on my phone. :rolleyes:

    I haven't noticed any interference at all through headphones and I use them every day. So there is definitely some kind of bug if there's no interference with headphones, but the line out from the dock causes issues. Why should the line out from the dock be any different than the headphone jack?

    If this were a known issue, wouldn't Apple put in their manual that you have to put the phone in airplane mode in order to get noise-free music output from the included dock?

    Just to be clear, you have to turn off the phone portion of the iPhone by putting it into airplane mode in order to eliminate the interference. Turning WiFi & BT off alone doesn't stop the noise.
  8. longofest Editor emeritus


    Jul 10, 2003
    Falls Church, VA
    I have updated the post to make it more explicit that I'm not implying the GSM interference is an iPhone bug, but rather just something iPhone purchasers should be aware of (that was my intention from the get-go).
  9. mkrishnan Moderator emeritus


    Jan 9, 2004
    Grand Rapids, MI, USA
    I think the new wording is fine, Longo. :)

    I, for what it's worth, have never really had serious interference issues with using my GSM phones. But I don't have a lot of unshielded speakers sitting around.... The biggest limitation is the generally worse issues inside large buildings. But then, that's a case of a worse version of something that's problematic with all cell phones.

    One small *advantage* of the GSM frequency range is that it's completely separated from the frequencies that BT and 802.11 use, so you don't have to worry about crosstalk or spreading in that range.
  10. ToddW macrumors 6502a

    Feb 26, 2004
  11. Nicky G macrumors 6502a

    Nicky G

    Mar 24, 2002
    Baltimore & NYC
    Did you read the post about Faraday cages? This is not the iPhone per se, it's the unshielded speakers themselves that are susceptible to the issue. The ear buds do block this interference, so that is why you are not hearing it there. Again, it's not the dock, it's the speakers themselves and their associated electronics... If you want to "blame" Apple, blame them for going with a GSM cellular provider. I would have preferred Sprint myself, but hey, as they said in a song: "You can't always get what you want..."
  12. freakout110 macrumors newbie

    Jul 12, 2007
    Longhorn Country
    My iPhone Problems

    I've had a couple of problems with this iPhone (8GB) and I was wondering if anyone else has had these problems.

    Problem #1 - While in an application (safari, mail, or google maps), there are times when the phone randomly goes back to the home screen. Particularly annoying when one is in the middle of something. At first, I thought that something was wrong with the home button.

    Apple Store Solution - They told me that it was not the home button, but a software problem. They assured me that factory restoration would fix the problem. After the first restoration, the problem still persisted. After the second restoration, I haven't had any problems, yet.

    Problem #2 - (Random shutdown just happened 20 minutes ago) I'm working away listening to music on the headphones and the phone just stopped playing music (the WiFi is off if that makes any difference). I pressed the home button, and nothing. I pressed the power button, and nothing.

    My solution - I pressed and held the home and power buttons and the phone restarted.

    Should I push the Apple Store to hook me up with a replacement or should I "let it ride"? I'm a little wary of letting it ride since I've already had these few problems in the first two weeks.

    As a full disclosure, my wife also has the same model iPhone and she hasn't had any problems, yet.
  13. justflie macrumors 6502a


    Nov 29, 2005
    Red Sox Nation
    meh, just hold it. I think those are software bugs, I get it too, even after a couple restores. They'll be fixed in the first update (hopefully)
  14. nagromme macrumors G5


    May 2, 2002
    These "morse code" bursts sound very much like what my parents' Sony-Ericsson phone does in their car--only that phone has no data functions. It happens when the phone is connected to the car via Bluetooth I think. At the time I wondered if it was my iPod/iTrip. Maybe it's the combination!

    I've heard the same sound while riding a city bus (with no iPod) and always wondered what it was. Now I'm thinking it's someone's phone interfering with the bus PA system.
  15. dasmb macrumors 6502

    Jul 12, 2007
    Today, I plugged my iPhone into the docking station of my work computer, a Dell Latitude. Just charging it, I'm sync'd with my MBP at home.

    About thirty minutes after I plug it in, the phone attempts to check my email. Immediately it starts belching RF interference back up the USB cable, causing distortion in the image of my crummy old CRT monitor. At first I thought it was kind of cool.

    Then the machine locked up.

    So, no more charging via the docking station. I'll use my car charger instead.
  16. schuylerc macrumors newbie

    Jun 30, 2007
    it's not just poor quality consumer grade electronics that receive the interference - most high quality studio monitors (speakers) for pro audio work are also susceptible, at a range of about 2 or 3 feet. the simplest solution is to move the phone away from the speaker. once it's about 4 or 5 feet away, the interference is negligible. i just make people shut off their phones at the mixing desk, and this generally solves the problem.

  17. benspratling macrumors 6502

    Jan 16, 2006
    We had a similar problem at my church - they ran the unshielded vga cable to the projector alongside the cables to the bass speakers - we got the 60 Hz power hum from the MAINS running up the screen which would distort when the bass guitar hit a big note. It took them 2 years to believe separating the cables by a few feet would actually solve the problem.

    Also, back in high school, we had lots of problems with cell phones interferring with the sound board & speaker amps. That's why they ask you to turn your phone "off" and not just put it on "silent." But eventually, since people won't turn them off, they bought better sound boards that are shielded. :)
  18. Ghibli macrumors regular

    Jun 5, 2005
    Trieste - Italy
    It's just the gsm phone talking with his GSM station (I think it's just a "I'm alive" signal). This same kind of sound bursts out some seconds before an incoming call. Just keep the phone away from speakers.


    (no iPhone, but a GSM phones user in Italy for the last 10 years...)
  19. Yankees 4 Life macrumors 6502a

    Jun 25, 2007
    College Station, Tx
    um guys, welcome to GSM life.. i've had GSM since 1998, and this happens all the time. Like some one said earlier, its just a beaming signal any gsm phone sends to its tower. I dont own a set, but you can get shielded speakers, it works, i tried it at best buy. Second, bluetooth has nothing ot do with the signal, bluetooth is on a different frequency, so there shouldnt be any interference. Last, CRT monitors are easily affected by the GSM frequencies because they arent shielded, so you're going to have to get used to the interference.
  20. iblown macrumors newbie

    Jan 3, 2008
    not a bug

    What IS a bug is that Apple should let you turn off GSM Time Syncing when you have the device plugged into a dock or you are playing music.

    The sound you hear is your phone syncing up its time over the cell phone network. Its not "general" GSM interference as you do not get this interference when making a phone call or using the phone. Its only when the phone syncs its time. Which is not something it should really need to do that often.

    Anyway, considering I was going to buy a 500 dollar dockable denon shelf system for the thing, I am now reconsidering unless they make airplane mode turn off the offending time sync so that my expensive radio will NEVER get that interference.

    Also, its NOT a shielding problem. Why the FCC allowed this frequency to be used is a better question. There is NO amplified speaker system that will not be affected by this if the phone is close enough.
  21. wongl macrumors newbie

    Dec 31, 2007
    London, UK
    What you hear is several consecutive transmission bursts (approx 4 or 8 x 4.7ms apart) of the GSM mobile terminal sending its location update to the BTS tower to let the GSM system know where it is and that it is still switched on and reachable. Often these bursts are pickup by unshielded speakers, or more likely by unshielded wires such as speaker wires or AV wires which are then amplified before the speaker cones.

    The interval for location updates is under the control of the BTS tower and not the mobile terminal. In GSM phase-I, the location update interval can range from 6 minutes to just over 24 hours. The actual value is up to the network planners, ATT in this case. Suffice to say that location updates are manadatory under the GSM system and the GSM Type Approval tests go to some length to verify that the mobile terminal conforms to the interval commanded by the BTS. So this is not something Apple can simply turnoff or modify the interval unilaterally without breaching the GSM Type Approval.

    If the GSM networks fails to receive a location update from a mobile terminal when it is due, the network may deem the mobile station as unreachable and proceed to divert all incoming calls to voicemail. In practice the network may allow one or more missed location updates before it takes such drastic action! Again this is up to the network planners/operators and could vary from network to network and even from location area to location area within the same network!

    You can sometimes also hear this bursting when the BTS is paging the mobile terminal with an incoming call or SMS text as the GSM system uses a similar frame structure to setup a call with the mobile terminal. Once in a call however, the phone transmitts continuously every 4.7ms which can be heard as a continous buzz (if it is near enough to an unshielded wire or object).

    In airplane mode the GSM mobile terminal functions are not enabled and so no location updates will be transmitted by the mobile terminal.

    Hope this clears up the understanding around this subject.
  22. balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    Great post wongl.

    The key to that is the proximity.

    Don't forget that the strength of the radio signal drops off like the square of the distance between the phone and the unintended receiver. http://en.wikipedia.org/wiki/Inverse-square_law#Light_and_other_electromagnetic_radiation So, when you move it back to twice the distance you reduce the signal by a factor of 4.

    The amplifier in the speakers is the one creating these signals from the "bursty" radio frequency signal the phone is using to talk to the base station. This also introduces a lot more sensitivity to position since these kinds of product will typically vary like the cube of the interfering signal. http://en.wikipedia.org/wiki/Intermodulation

    So moving the phone to twice the distance, lowers the interfering signal to 1/4 of the original strength and the products generated in the output of the speaker by a factor of 1/64 (1/(4*4*4)).

  23. megfilmworks macrumors 68020


    Jul 1, 2007
    Sherman Oaks
    Now that is a great and informative post...thanks!

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