Blog Post

iPhone 4 Attenuation Only Half the Story

Something about Apple’s press conference yesterday just didn’t sit right with me. Apple (s aapl) 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.

76 Responses to “iPhone 4 Attenuation Only Half the Story”

  1. I’d be interested to see how the bars react after the phone is updated to 4.0.1.
    The bars in this example is pre-update. Perhaps the update might give you an extra bar or two.

  2. Shaking Head Sadly

    What you are missing, Mr. Radioman is that the bridging of the two antennas does not simply change antenna length–the “wrong” antenna is connected internally to additional circuitry. If both were “pushing” a signal at the same time you will experience a degradation of performance far in excess than the change caused by sub-optimal antenna length.

    Seriously, is there any editorial review at TAB? Can i be qualified to write a column because I saw something on Mythbusters or heard a podcast once?

    Content FAIL.

  3. As a loyal Apple customer and believer, my gut feeling was one of disappointment and let down. My new iPhone 4 drops more calls than ever, and every time I think of the horrible coverage AT&T delivers, I just wonder when the stars will align one again – a phone that works all the time so I can live and work and function, and….verizon. I wish Steve Jobs had come clean completely and offered a true fix that does not cover up the beauty of the phone I paid for.

  4. Oh good, another blogger who thinks they have all the answers and surely have discovered what the Apple engineers were unable to. And look, another blogger thinks the same thing so it must be true! Bloggers surely must be the most respectable engineers on the planet if they were able to figure out such a major flaw so easily..

  5. Onitsukatiger

    Nobody is perfect. No company is perfect. If people want to crucify major players. Look for answers there. What we’re seeing here is not only the milking to the death by the media but atypical damage the popular one behaviour. People need to put up with what’s not perfect. I cannot believe there are those still whining and complaining, it goes to show:
    a) your expectations of technology companies is unrealistic
    b) you are susceptible to media frenzy
    c) you have done no research, have little to no business acumen, and certainly no tech knowledge
    And it doesn’t take a person with knowledge, simply sense, to realise if we need to be pointing fingers, point it at yourself. Half of these people are very very offended by Apple’s success. Half these people desperately want a reason to be anti-is-trendy. They must have missed the Apple boat to begin with, so now Android is coming up, let’s disrespect Apple so we can move the market share and feel better about our personal choice.

    • I’m sorry that the article left you with that feeling. I’m not trying to disrespect Apple, I was just trying to explain what I thought was another interesting part of their iPhone design.

  6. HAL9000

    The problem with all of these stores explaining how Job’s explanation is wrong is that it is extremely easy to reverse engineer a scenario to arrive at a known result. Just because you can make sense of it another way in your head does not mean that’s the real root problem. Every blogger and commenter now thinks they are each individually smarter than Apple’s entire engineering team. It’s simply beyond logic.

  7. Don Wise

    I have to agree with someone else’s post; this is not so much a design issue as the problem points back to AT&T and their network coverage. No one is mentioning this in much measure on any of the blogs. The phone is doing exactly as it was designed to do. I migrated from v.3 to v.4 and still have the same dead zones that I had in here Los Angeles as before – there’s little to no improvement in maintaining connectivity in these areas. That’s a real world qualitative study.

    It’s not the phone, it’s not the bars, it’s not the antenna, it’s the network.

    • I’ve read a few blogs where people are saying that they are getting even better reception with the iPhone 4. The network certainly has something to do with it, and seems to be a reason why its such a difficult issue to nail down. Its inconsistent.

  8. It’s nice to know the science behind why the antenna design doesn’t work. But all users really care is that when they put their thumb over the gap, reception drops. With a consumer product such as this, that’s really all the “science” that matters. So thanks for the added info–but I think the reason Jobs left out that “half of the story” is that it’s really not relevant to us as his beloved “users.”

  9. alphacheck

    Are people complaining that when the short circuit the antenna reception drops? Here’s the answer, don’t do that. Why would you put your iPhone 4 in a pocket with keys?

    I can reduce the signal for both WiFi and Cell by changing how I hold it. It’s a phone, with an antenna. Any antenna’s gain varies with direction, or interference. It’s physics. The goal is to have enough SNR to endure the variations, not to have the antenna always operating at peak gain.

    BTW, if you stick the phone in a bucket of water it doesn’t work either, but I encourage verification testing. Perhaps then we’d have fewer whiners.

    If you don’t like it, take it back and get a different phone.

  10. Saying don’t buy the phone is a dumb answer. Returning it or not buying it is a stupid solution because through no fault of the consumer, they have to give up something they have waited for, for so long. Especially to loyal Apple enthusiasts like myself, I have been using a screwed up blackberry for 3 months now in anticipation of the iphone 4. When I pay 700 or upwards for something, I expect some level of quality if nothing else. Returning it or not buying it does nothing to ease the fact that its still something I want or wanted really badly. I’m still going to get it, regardless of the antenna issue….but that does not make me any less upset as a die hard Apple fan or a consumer in general.

    • !! I can’t believe this attitude. Companies put out products at a given price, and it’s up to you, the consumer, to decide if the value provided at the price asked is good enough to buy it or not. I don’t recall seeing any Apple henchmen dragging people into the store to buy an iPhone under duress. No-one is making you buy anything – no matter what you want or how desperate you are for something. Either the iPhone 4 lives up to your pent up desperation or it doesn’t. If something else out there is better for the price, then buy it instead.

  11. Thing is, your hand is *not* a good electrical conductor. That’s why he is using a key. Only when your hands are wet or very sweaty your skin is conductive enough to do this trick.

  12. Gilbert

    Why does it only happen when touching the antennas at that point. Why not when you hold the phone normally touching both sides of the phone and therefore both antennas. What’s so special about that particular spot. Surely, from my limited knowledge, touching any antenna upsets it’s tuned length.

      • William 3.0

        Just based on an electronics hobbyists knowledge (changed from EE to CS before signing up for classes too many years ago) but the length and width of a resistor is also a factor in its resistance. Bridging the gap with a couple millimeters worth of skin affects the antenna but traveling the length of the fingertips to the palm does not.

  13. no name

    What didn’t set right with me about this press conference is how Jobs used AppleCare data and questionable dropped call data to tell us that there is NO issues with iPhone 4, “But to make you shut the F up, we will issue free bumper cases. Happy now?”.

    Most people do not call AppleCare or go to Genius Bar with iPhone reception issues because they know that they will be told “Everything if fine. Kthxbye”. That certainly has been my experience for the past 2 years.

    • As a former Mac Genius, I’m offended by your statements. Yes, Apple customers do indeed call AppleCare, and go to the Genius Bar. For the most part, Mac Geniuses are very dedicated to making things right for the customer, even if the managers don’t always agree with the course of action. Unlike you, I worked for Apple for four and a half years. I saw from the inside how Apple handles problems for customers. There’s a reason why Apple scores so high on customer service surveys. It’s because they’re the best. If a customer has a problem, and they don’t give Apple the chance to fix the problem before they start whining on YouTube, or the blogs, then they become part of the problem. This whole issue was crap from the very start. Apple is being very generous by offering a free case, and it’s stupid not to have one anyway. In my opinion, if you haven’t given Apple a chance to fix the issue for you, then you don’t deserve a damned thing. Return the iPhone if you don’t like it. Otherwise, shut the hell up! This issue needs to die, and the “Apple Blog” needs to let it. I guess the advertising revenue from the ads that my ad blocker is blocking is too tempting for them to stop harping about “antennagate”. I hope you don’t consider yourself “journalists”. You’re not.

      • I’m not formally trained in journalisim, so no, I’m not a journalist. I’m simply a fan of Apple with a technical background who loves to write, so I’m a blogger.

        For the record, I absolutely love the Genius Bar. Almost every time I’ve been in our local Apple Store they have taken better than expected care of me.

        As for the issue being discussed, the article was about talking about what unique problems wrapping the antennas around the outside of the case brings.

  14. I agree, showing us problems with other smartphones is not going to solve what is wrong with the iphone 4. Thank you for the article, solidifies my perception that perhaps instead of working on fixing the hardware aspect of things on this iphone 4, they will somehow end up re-making another generation iphone 4, and all of us stuck with these ones are going to have to hang tight and do nothing.

      • Wendell

        Agreed. Take the phone back if you don’t like it. 5 to 1 says you keep the phone like the 98.3% of other iPhone 4 owners.

        The story is a non-issue created by non technical blogs that claim to understand antenna design.

    • GlennAC

      For you and all the others, then what would have satisfied you? It appears that nothing Apple could have said or done would have satisfied the detractors short of a total product recall, Apple’s abandonment of the iPhone 4, and their pledge to try better next summer.

      While that may have gratified a small vocal minority, I imagine the 99% of satisfied users would object. So tell us, what else can Apple reasonably be expected to do for a product that the vast majority are entirely satisfied with?

      No, I’m serious. What else could Apple have done to appease the dissatisfied while at the same time not pissing off the majority that are perfectly happy with the product?

  15. This post proves my point that it doesn’t matter what Apple says. People will still complain. This blog exists because of Apple, and for you to continue trying to keep this story is just shameful. Apple is not above criticism. I’ve criticized them for a lot of things in recent years. However, I don’t keep bashing them when I know they’re addressing the issues that I’m angry about. Like the writing of this post, I was also trained the the U.S. Navy on radio technology. I see nothing incorrect with what Apple has demonstrated. This whole scandal is B.S. No one that I know has had a problem with their iPhone 4. I used mine for 8 days without a case. Why in the hell is it so hard for people to simply hold the phone a different way? Get over it!

    • For some reason your post reminds me of that ‘Leave Brittney alone!’ video.

      Anyway, it’s a problem. You don’t get 16,000 people calling a helpline if it isn’t. However, the iCondom will sort it – as long as you’re OK being laughed at – and the next batch in September will sort it out.

      I think it’s great that the early adopters find these issues for me so when I get mine at Xmas it’ll all be roses. :)

  16. One question I would like you to answer, is this issue occurring in other countries? If not this is not an iPhone issue but is an AT&T issue of poor coverage.

      • My friend just moved to Boston from Toronto. He picked up an iPhone 4, and noticed the “death grip” issue right away.

        He cannot however, reproduce it when he’s back in Canada. It only seems to happen to him when he’s in Boston on the AT&T network.

        Others have reported similar behaviour – the most notable being David Heinemeier Hansson of Ruby & Rails fame, who can reproduce the issue on his iPhone 4 in the US, but not when he’s back home in Denmark (here’s his tweet about it:

        Now obviously the laws of antenna physics don’t change between countries. The attenuation issue is still there in both Toronto and Denmark, but is not having as much of an impact in both these cases.

        My guess? Just overall better cellular coverage in Toronto and whatever city DHH was in, which nullified the problem as a whole.

        I’m going to pick one up when they’re released in Canada later this month and I’m curious to see whether I’ll be able to duplicate my friend’s “success” here on our west coast.

  17. Michael

    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.

  18. 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

    • Jennifer

      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.

  19. 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.

    • 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.

      • 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?

    • 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!!!

  20. Wendell

    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?

  21. 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.

    • 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 . . . .

  22. 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.

    • 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.

  23. 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”.