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Why Your Clock Radio Is All Abuzz About iPhones 397

Posted by CmdrTaco
from the i-hate-that-sound-so-much dept.
blackbearnh wrote in with a story that's not really about the iPhone, but if your office speakerphones beep like mine does, read on: "If you own an iPhone, you may have noticed that it has a distinct and very annoying effect on clock radios, computer speakers, car radios, and just about anything else with a speaker. The folks at O'Reilly Media aren't immune, so they set out to discover just what is it about iPhones that makes them such bad RF citizens. The iPhones aren't the only bad apples in the cell phone basket and there's not much you can do about the problem. We're really in an interesting time in that there has never been so many high-powered personal transmitters just wandering loose in the world."
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Why Your Clock Radio Is All Abuzz About iPhones

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  • GSM Buzz (Score:5, Informative)

    by russotto (537200) on Monday October 27, 2008 @12:03PM (#25528457) Journal
    It's not just the iPhone. It's any GSM phone. Google "GSM Buzz". Meet the "GSM Devil", which relies on this interference to tell you you're phone is about to ring. http://shop.mopodmania.net/product.sc?categoryId=1&productId=15 [mopodmania.net]
  • by Nick Ives (317) on Monday October 27, 2008 @12:03PM (#25528465)

    Maybe it's just because you guys aren't used to GSM cellphones but over here in the UK everyone recognises that noise. Anytime you put a mobile next to speakers you get that noise.

    Welcome to the 1990s, America!

  • by sznupi (719324) on Monday October 27, 2008 @12:05PM (#25528505) Homepage

    ...everything regarding cellphones? Including, in this case, sometimes annoying side effects?

    This is nothing new...especially if, on any other phone, you have also kept semi-constant GPRS connection.

    PS. Rearranging speaker cables/etc. eliminates the problem anyway...

  • by Spazztastic (814296) <spazztastic AT gmail DOT com> on Monday October 27, 2008 @12:06PM (#25528517)
    Mod parent up. Cell phones have been doing this since my old Nokia to my new Blackjack II.
  • by HeavyD14 (898751) on Monday October 27, 2008 @12:15PM (#25528713) Homepage
    Yeah, those are called Chokes: http://en.wikipedia.org/wiki/Common_mode_choke [wikipedia.org]
  • Re:Huh... (Score:5, Informative)

    by russotto (537200) on Monday October 27, 2008 @12:16PM (#25528737) Journal

    Maybe it's because the computer speakers are so old that they're actually still shielded (unlike most today?)

    Yes, speakers which are magnetically shielded to prevent affecting CRTs will also likely reject the GSM buzz.

    The clock radio would only pick up the GSM buzz if the speaker was on (radio or buzzer); when it's off, no problem.

  • by AdamWeeden (678591) on Monday October 27, 2008 @12:18PM (#25528771) Homepage
    Yes, this is a pain in the butt, but as others have noted, it's nothing new. I've been having this issue since my first AT&T (formerly Cingular), i.e., GSM, phone. There is a trick to fix this though: magnets. Simply loop your speaker wire through a magnet, as this article [gizmodo.com] indicates.
  • Re:FCC Rules Part 15 (Score:5, Informative)

    by leighklotz (192300) on Monday October 27, 2008 @12:19PM (#25528797) Homepage

    whatever happend to the label on the bottom of everything, which states that:

    "This device complies with Part 15 of the FCC rules. Operation is subject to the following two conditions: (1) the device may not cause harmful interference, and (2) the device must accept any interference received, including interference that may cause undesirable operation."

    obviously the folks that made my PC speakers obeyed those rules, so why is apple getting away with breaking condition 1?

    The iPhone isn't operating under Part 15. It's licensed. Your cell provider holds the license from the FCC. They paid a lot of money for it; remember the spectrum auctions that raised billions. It's your speakers that have to live with the licensed world, not the other way around.

    The same is true for broadcast radio, TV, police, fire, ambulance, business radios, taxi dispatchers, amateur radio, military, and even foreign licensed broadcast systems. Your speakers have to live with it.

    You might try (1) using twisted pair instead of zip line to your speakers and (2) using ferrite bead clamps, a few turns wrapped around both ends of the speaker cable. But it probably won't help, as it's likely your speakers internal amplifier is picking up the signals directly, as they're cheaply made (see TOA) and poorly shielded.

  • by Anonymous Coward on Monday October 27, 2008 @12:21PM (#25528825)

    It's not a magnet. It's ferrite.

  • by fermion (181285) on Monday October 27, 2008 @12:24PM (#25528883) Homepage Journal
    It is not just GSM phones. My old RAZR had the same problem. At meeting, anytime a phone rings we get all sorts of interference with audio.
  • Not on 3G, EDGE only (Score:5, Informative)

    by yabos (719499) on Monday October 27, 2008 @12:28PM (#25528953)
    The GSM buzzing is all GSM phones but I noticed on my iPhone that using 3G it goes away. From what I've read, the loud noise is caused by rapid turning on/off of the GSM transceiver which creates EM pulses.
  • by timster (32400) on Monday October 27, 2008 @12:43PM (#25529265)

    You don't quite understand the cause of the problem -- it's not that phones are transmitting on the wrong frequency or "splattering" the spectrum. It's that devices like unshielded speakers are prone to pick up interference like this from all across the spectrum, including the GSM bands.

    Cell phone transmitters are much more heavily regulated than consumer electronics like clock radios.

  • by sexconker (1179573) on Monday October 27, 2008 @12:43PM (#25529275)

    SOS for the Morse intolerant.

  • by orclevegam (940336) on Monday October 27, 2008 @12:48PM (#25529351) Journal
    As the AC pointed out it's not a magnet, it's a ferrite bead [wikipedia.org]. This is a very common thing, and many cables come with one installed already. Just looking at the monitor sitting on my desk I can see a pair of beads on it's VGA cable (one at each end), and they're very common in most high end speaker systems. For cables that don't have them you can pick them up from various places in the form of snap-on cylinders which can either be directly clamped onto the cable, or alternatively you can wrap the cord around the bead once or twice before clamping it, which will hold it in place on the cable and also serves to improve the filtering slightly.

    They're a very simple passive device that works by disrupting high frequency RF passing through the cord. Since any large (long) conductor can function as an antenna, most cables are really just giant antenna, so adding a ferrite bead is a really cheap and simple way to counteract this. As for interference within a speaker itself (that is, not arriving by way of the speakerwire used to hook it up) there's not much you can do other than putting a Faraday cage around the speaker, or just moving the source of noise farther away from the speaker.
  • Re:FCC Rules Part 15 (Score:3, Informative)

    by wramsdel (463149) on Monday October 27, 2008 @01:06PM (#25529665)

    Leighklotz is exactly right, but it gets even worse. Even a Part 15 device, using similar modulation to the GSM phone, could likely cause interference to your speakers. I have a DECT phone, compliant with FCC Part 15, sitting next to my computer speakers, and it creates a nice buzz when it's searching for the base. That's not the phone's fault, I'm sure they're transmitting all their energy in the allowed band, but nonetheless my speakers are rectifying that RF energy and amplifying the resulting envelope. The "device may not cause harmful interference" part of the Part 15 regulations refers specifically to spurious emissions outside the permitted band(s) of operation. Unfortunately, inexpensively made or carelessly designed electronics, which constitute the bulk of consumer offerings, often don't include much protection from interference. Regardless of whether the interfering device is operating properly or not, these devices will suffer.

  • Re:Psh (Score:5, Informative)

    by Detritus (11846) on Monday October 27, 2008 @01:11PM (#25529745) Homepage
    You wouldn't get interference if your television receiver wasn't a POS. We know how to design and build receivers that can operate in hostile RF environments, we just choose not to, because it's cheaper to build the POS.
  • by billcopc (196330) <vrillco@yahoo.com> on Monday October 27, 2008 @01:44PM (#25530335) Homepage

    It's not so much the computer as it is the speakers themselves. The long cheap unshielded speaker wires pick up GSM interference, whose lower harmonics result in that distinctive buzzing sound. The speaker wire basically acts as an antenna.

    Digital speakers obviously don't suffer from this phenomenon, but they're hard to find outside of pro-audio circles and the occasional cheapo USB speaker set.

  • Re:Psh (Score:3, Informative)

    by theaveng (1243528) on Monday October 27, 2008 @02:23PM (#25530961)

    Except that when an Ipod (or other WSD) is broadcasting on channel 18, not all the signal stays inside channel 18. A lot of it spills-over into WPHL's channel 17. Think of them as the EM equivalent of harmonics of the original signal.

    So you cannot place two broadcasts directly side-by-side and expect it to work. This is not a flaw of design. This is a flaw of nature. "You cannae change the laws of physics" is a favorite joke from Star Trek, but it also happens to be true. A DTV receiver cannot decode WPHL-17's signal when the Ipod/WSD on channel 18 is overflowing its own signal onto the channel.

  • by labnet (457441) on Monday October 27, 2008 @04:24PM (#25532697)

    So the poster is correct. It is a 217Hz RF pulse with about 500uS pulse width.
    Cell phones use an electric field antenna which produces a high near field electric field that decays at 1/r cubed, and a propagating electromagnetic field that decays at 1/r.
    It is most likely the near field electric field (capacitively coupled) that is consequently demodulated by any non linear components in your speaker amplifiers as the PA (Power Amplifier) in the phone changes power level.
    Even though the electronics industry is one of the most regulated in the world with a zillion tests, there is no mandatory test for effects on electronics from near field coupling of transmitters such as mobile phones.
    I had a product many years ago that passed all the regulatory tests, but would fail when put right up to a mobile phone. Adding a 47pF cap to the clk line an external EEPROM solved the problem.

  • Re:FCC Rules Part 15 (Score:3, Informative)

    by leighklotz (192300) on Monday October 27, 2008 @10:18PM (#25536487) Homepage

    Your speakers have to live with it.

    You might try (1) using twisted pair instead of zip line to your speakers and (2) using ferrite bead clamps, a few turns wrapped around both ends of the speaker cable. But it probably won't help, as it's likely your speakers internal amplifier is picking up the signals directly, as they're cheaply made (see TOA) and poorly shielded.

    What will twisted pair do ? Doesn't twisted pair only protect against interference when you have a balanced line [wikipedia.org] with opposite voltages going down each wire?

    Read this, page 2 [audiosystemsgroup.com]:

    If the cable is an unshielded pair (loudspeaker cable, for example), RF will be induced approximately equally on both conductors (but, depending what the input circuit of the equipment looks
    like at RF, current flow into the equipment may not be equal on both conductors). This can also
    produce a differential voltage at the input (or output) terminals.
    Output Wiring is Important Too! It is well known, for example, that RF interference is often coupled into the output stage of audio equipment -- for example, the power amplifiers that feed loud-speakers or headphones. There is always feedback around that output stage, so RF present at the
    output will follow the feedback network to the input of a gain stage, where it will be detected and
    amplified. This problem is made much worse when parallel wire cable (zip cord) is used to feed
    the loudspeakers or headphones, and can usually be solved simply by replacing the zip cord with a
    twisted pair of POC (plain ordinary copper). [Pseudo-scientific advertising hype for exotic cables
    notwithstanding, it was shown nearly 30 years ago that #12 copper twisted pair (or #10 for very
    long runs) is a nearly ideal loudspeaker cable.]... As we will discuss later, the twisting of a pair greatly reduces the
    level of RF that the wiring couples to circuitry.

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