Something about Apple’s press conference yesterday just didn’t sit right with me. They seem to be doing the right thing by giving out the free bumper cases, but how they explained why the cases are needed in some instances didn’t quite cover everything.


Something about Apple’s press conference yesterday just didn’t sit right with me. Apple has put up a page with videos of various other smart phones displaying the same type of behavior when griped in a certain way. It also has put up a page where its explains its $100 million dollar testing facilities it uses for testing reception and signal in various conditions, just to let us know how much the company cares. Steve Jobs said that they love us. They seem to be doing the right thing by giving out the free bumper cases, but how they explained why the cases are needed in some instances didn’t quite cover everything. Attenuation is only half the story.

Way back when, a couple of lifetimes ago, I was a Radioman in the Navy, and as part of my education and advancement requirements I had to study antenna and wave propagation theory. For the sake of brevity, I’m going to over-simplify this to the point where real engineers might get a headache if they continue on, but here goes anyway.

Radio signals traveling through the air look like waves if drawn on paper. These waves travel at a constant speed, the speed of light, so to send more waves through on a signal, the waves must be smaller. The number of waves traveling along a signal is referred to as hertz, and the size of the wave is its wavelength. The antennas used to generate and receive these waves need to be the right size, and the right shape. Back when I was in the Navy, we were transmitting waves that required a 35 foot whip antenna because we were transmitting in the High Frequency (HF) range. As the frequency of the wave gets higher, the size of the waves and the antenna used to transmit and receive them become smaller, and more precise.

Cell phones operate in the Ultra High Frequency (UHF) frequency range, so the antenna that they use is much smaller than lower frequency transmissions. The iPhone 4 has two antenna that wrap around its case, one for cellular use and the other for Wi-Fi and bluetooth. The two antennas are separated by the small gap in the lower left hand side of the case, which Apple has identified as the antenna’s most sensitive part. This is true, in part because of the attenuation (or “blocking of the signal”) when you put your hand over the gap.

The other part of the equation that Apple is not talking about is that while your hand doesn’t make a particularly good medium for radio waves to travel through, it does make a fairly good electrical conductor. When you place your hand over that gap, you are actually bridging the two antennas together and making a larger antenna. A larger antenna that is not the right size for the frequency of AT&T’s cellular network, and the bars drop right off.

I don’t have the equipment on hand anymore to test this, but the video below, linked to by an expert on antennas (via Daring Fireball), seems to show the behavior I would expect. At around the 1:30 mark, a key placed over the gap drops the iPhone 4’s reception down from five bars to one, and the narrator says that eventually there will be no signal at all. When the key is removed, the bars return.

The free bumpers solve both problems for the iPhone 4. They prevent the antenna gap from being bridged by anything conductive, and they give a little more room between the antenna and your hand, to help with attenuation. Unfortunately, the bumpers do not address the actual design of the antenna. It may be possible for Apple to move the antenna gap to a different spot on the phone in future revisions of the iPhone. For example, why not put the antenna at the top of the phone where people are less likely to hold it? As answered by AntennaSys in the link above, physical placement of the antenna is mandated by the FCC. If bridging the antenna gap is the problem, it may be possible to move the gap to the bottom of the phone, but since that would change the shape of the antenna, I’m not sure if that’s possible or not. Anandtech has a beautiful solution using Kapton insulating tape, which makes the iPhone look like it’s been plated in gold. If Apple were to add a layer of insulation to the iPhone, that might alleviate the symptoms.

I’m not the only one who thought that Apple’s explanation seemed lacking. TidBITS writer Rich Mogull has a very detailed article where he draws a similar conclusion. If you’d like to know more about the issue, I’d suggest dropping his article into Instapaper. If you’ve got any ideas about the iPhone 4’s antenna “situation,” I’d love to hear from you in the comments. Especially if anyone can reproduce the key trick from the video.

  1. And -

  2. And –

    if you were as much of a news junkie as I am, you could note that a number of tech geeks acknowledge that the FCC espouses a protocol which requires the mounting point for the antennae to be pretty much where it is. Down in that corner.

    And –

    John Gruber asked Jobs et all if they had resorted to using a bumper on their own phones. The answer was “No”.

    He added – “neither have I”.

  3. caretaker@mac.com Saturday, July 17, 2010

    do yourself a service and stop biting on the hand that feeds you..

    1. If we are critical of Apple, its because we hold them to such a high standard. We love Apple here at The Apple Blog, but not everything they do is perfect.

    2. You would honestly prefer Apple blogs to simply post glowing reviews of all Apple products and ignore problems and other negative aspects of the company and their products? Obviously there are plenty of people out there openly hating on Apple, notably fans of Apple’s competition, and I would love to see unjust criticism proven wrong.

      However, when there is a problem, then there is a problem, and I would I would much rather see people show integrity and report what’s going on, and not just what makes Apple look better. By pointing a critical eye at Apple, or any company for that matter, we the users give them a reason to improve their products in the next generation, and not make the same mistakes.

  4. Well put your thumb over the gap and yes its resistive at DC, what about UHF… explain a folded dipole, which if measured with a multimeter would be a short circuit.
    The thin plastic case that surrounds the majority of phones is transparent to radio waves, its the application of a hand or head to any phone will affect the signal strength being received.

  5. Of course it doesn’t sit right with you; the tech media wants to keep milking the non-story to get more page views. As an iPhone 4 owner, it’s signal reception is light years beyond what I had with the 3GS. Now that you’ve got Apple to hand out free bumpers, can you help out the Android folks now? There’s always videos posted that show you can duplicate the death grip on the NEW Droid X.

    1. Maybe someone can help Android users with their crashing apps.

      Lets face it, Apple said they were still studying the Antenna and trying to continually improve it. They set a date of September 30th for the bumpers, so lets wait and see what happens then.

      Perhaps we can talk about the technology being used to clean the gulf oil disaster . . . .

  6. you’re making a big deal over nothing.

    the issue is perception not hertz or antenna design. apple is a victim of their own success. any error that they make is magnified due to the pure adoration people have for their products.

    the difference between the samsung, htc and blackberry products is that they don’t have thousands of blogs that report their every move. not to mention the fact that their customers aren’t as happy with their phones when compared to apple users.

    there’s an issue here for sure but it’s not a big one. something like 89% of people love their iphone 4. the issue means more to the “tekky” and the media types but isn’t effecting most customers. seriously, i’ve never seen anyone hold their phone in a “death grip” for extended periods. my buddy’s bb bold is susceptible to the death grip as is my 3gs but we don’t suffer from dropped calls.

    all apple has done has brought an old technical issue to the mainstream media and blogosphere. the attenuation issue has been around for years and has effected scores of other smart phones. apple suffers because their products are magically supposed to be beyond perfect.

    everyone i know that has an iphone 4 absolutely loves the phone. isn’t that the reality?

    1. “everyone i know that has an iphone 4 absolutely loves the phone. isn’t that the reality?”


  7. Does this phone have the 4.0.1 update?

    1. That would have absolutely no effect as this is a HARDWARE problem and not a software problem.

      1. In fact it does have an effect. It’s changed how the iPhone drops calls of a specific level. My iPhone 4, for a fact, is now less likely to drop calls in certain marginal situations. My desk at work for one is now showing 1 or 2 bars where before it showed 1 or no network at all. I always thought it strange I could recieve calls before when it shows no network, but now it’s costantly showing 1 or 2 bars at my desk.

        Could it be that the threshold for dropping calls was simply too high, and now its more accurate and holding calls that could have been held before but were not?

    2. to answer your question- no, it doesn’t have the update. It has the 4.0.0 bars, and if it HAD been upgraded you would not be seeing the drastic drop in bars. This person probably has reception that is at the very bottom of the scale of 5 bars, which is the main problem apple addressed in the update. If they had the update, they would probably be sitting at 3-4 bars, and only lose possibly one bar (or none) when doing this trick.

      Moral of the story? Apple clearly effed up because now we all have to stop holding a key against the side of the phone while we talk!! OMFG!!!

  8. I’m confused as to the value this conversation adds to the issue. The headline here seems misleading.

    I wouldn’t expect Apple to discuss this in a 30 minute press conference. As a layman on the issue, their explanation was sufficiently techy, but not overly so as to confuse and boggle down the masses who don’t write for tech blogs. Tech press may have been the only ones invited, but that press conference was meant to sooth the concern of the non-techy masses who had simply heard that iPhone 4 had some problems.

    Again, I’m not a techy, but am an avid reader of tech blogs & have followed “antennaegate” closely. I knew that the FCC wouldn’t allow the antennae to be placed at the top of the phone, as they believe the radio wave radiation could be harmful. Additionally, I’d already read about the conductivity and the shorting out of the antennae.

    The bottom line is that attenuation of the signal occurs when you touch any smartphone on the “weak spot” of the antennae. In a quest for innovation & beauty, Apple made this spot very visible to consumers. As a result, while the problem has always occurred, the direct cause could not be identified as most consumers don’t have intimate knowledge of where the internal antennae is located. This is obviously not the case with iPhone 4, and thus people, suddenly able to directly see the actual cause of signal loss, incorrectly attributed the issue only to iPhone 4, when in fact it affects all smartphones.

    A Bumper or any other case should solve the problem. End of story. Time to move on.

    1. I really didn’t think the headline was misleading, I’m sorry if you thought so. The value I was trying to add to the conversation was that while yes, attenuation is common to all phones, only the iPhone 4 has the antenna wrapped around the case, and that has it’s own issues.

  9. How about they make a small rubber stopper that presses into the gap with a small cover. Kinda like a stubby T-shape they will stop the connection ever being made. That way it could solve it without the need for an entire case

    1. That wouldn’t work, because the second you touch the antenna on either side of the rubber stopper, you bridge the connection again and you’ll have the same issue. Exposing the antenna is the poor design flaw they’re getting reamed for. If it wasn’t exposed, we wouldn’t be able to bridge the connections between them and experience signal loss.

      For the record, my original 4 did not have the Death Grip problem. My replacement does.

  10. I find it sad that you’re making a big deal out of bridging the antenna in the same post where you reference AnandTech’s latest article on the subject. In the section about the Kapton tape, it clearly points out – if you can do basic math – that 1/3 of the attenuation is due to bridging and 2/3 is due to having your hand present at the bottom of the phone.

    It can be granted that Apple is trying to minimize the bridging that happens, as they want to focus on what happens when your hand is near that area of the phone.

    It’s also laughable that anyone is relying on signal bars to be a reliable indicator of anything on any phone. If you’re doing doing something akin to what AnandTech did to have the phone display strength in dB, then your analysis is fundamentally flawed – even if your name is Consumer Reports. The only thing you can say without this step is that signal strength drops by some unknown amount, which is next to useless and is certainly true for any cell phone (as been amply demonstrated all over by now).

    The only reason that bridging will make any difference to anyone at any time is if the “extra” 1/3 causes you to drop a connection in an area where there’s a weak signal. Since the 2/3 loss is basically unavoidable without using Bluetooth. If the “extra” 1/3 doesn’t change your connectivity, then it doesn’t matter to anyone at all.

    The only possibly clue, at this point, on this is the data Apple presented from AT&T where the iPhone4 drops calls at a rate slightly higher than the 3GS. Even the antenna expert you sourced via Daring Fireball noted that the issue isn’t much of an issue at all.

    As an iPhone4 owner that can observe the attenuation myself that is often in an area of weak signal strength, my conclusion is that all the the tech blogs are latching onto this so-called issue because it gets eyeballs on their webpages due to the drama. Certainly since the proximity sensor issue seems both more widespread and a much bigger problem from an every day users point of view.

    1. Ok, so maybe attenuation is two-thirds the story, instead of half? :)


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