iPhone 'Death Grip' effect is real, plastic cases don't help The so-called 'death grip' effect, in which a user's hand touching a smartphone antenna degrades its radio connections - a major issue for the iPhone 4 with its external antennae - is real and is a serious problem, according to British boffins researching the matter. Furthermore they found that plastic insulation between hand …
Why does the iPhone 4 get a signal in places where my old Motorola didn't (just a week or so before)?
The thing about the iPhone 4's antenna design is the "weak spot" is marked with other "traditional" designs there is a "weak spot" but it hasn't got a line showing you where it is!
Now the iPhone 4's design isn't perfect, the thing is a bit "slippery", especially with glass on both back and front, but I don't think raw "network coverage" is really an issue - mine seems to find a signal in places where both Nokia and Motorola handsets didn't. Yes, we're talking about the same network.
No I don't use a case with the iPhone 4, and it's just "stock" not modified or weird (or white!)
What is really impressive is the battery life (for a smartphone). Putting the antenna assembly in the phone's main structural element does make room for a bigger battery.
This is the first step of such a project.
It may be that the results don't come as a surprise, but in order to gauge the problem, you need to perform controlled, scientific tests.
The next stage, which he has said he will be doing, is to find a way round the problem. This is much easier when you have accurate measurements to start with.
You are assuming that Apple can not and has not already chosen the best compromise to deal with this? Apple just slapped an antenna on the outside then said "oh that's why nobody else does that". Apple thinks more than any other company about what makes a plesant experience for it's customers. This design isn't a "mistake". It's a carefully considered compromise between phone size and reception. Apple isn't perfect but they also aren't sloppy when it comes to product design.
Errr......
Scientific research to establish that the presence of a large conducting body near an antenna will detune it or cause it to be mismatched to the characteristic impedance of the feeder ???
I think you might well find a large, if not massive, body of research showing this. Stretching back a good few decades, if not to the birth of RF Communications (well, post-spark transmitters anyways).
This is why MIMO doesn't work as well as it might - one antenna impacts on the performance of the other.
The general principle is not what was researched here. What was researched here was the specific effect under specific conditions.
We've known F=ma since before the invention of the automobile, but it wasn't until tests showed the results of application of that principle under highway collision conditions that auto manufacturers started thinking seriously about safety features.
As most of the actual Catholics are outside waiting to see the Pope. Those who have risen far enough up the power structure of the church to be in the Vatican in uniform on the other hand have got there not through being good Catholics but by being good politicians.
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There is no simple answer (as you might have guessed) as you have a number of conflicting aspects to antenna design.
In general, if you are talking about an electrically small antenna (i.e. physically much less than 1/4 wavelength, etc) then you might find that adding your fleshy touch improves reception by adding to the area able to intercept signals.
However, the converse aspect also applies (probably here), in order to make any antenna work efficiently they are normally in resonance (i.e. tuned to a specific narrow range of frequencies) and by touching them you de-tune them and so make the job of getting power in/out of them more difficult. In addition, the body is not a *good* conductor, so tends to make the thing lossy and not only to re-tune it to a different frequency.
Over all I expect flesh decreases reception.
The iPhone problem is certainly *not* unique, just that the close proximity of the antenna to the hand makes the effect significantly stronger, and on top you have Apple's attitude to the problem with their high-end device where style has prevailed over best-practice RF engineering.
The conductivity of skin to stainless steel is so low it can be discounted. What is more likely is you're creating a capacitance, but any antenna reasonably close to a plastic case would have the same effect (and in fact this appears to be true as the issue isn't unique to the iPhone 4).
Where the iPhone 4 is different is the spot where this is most likely to happen has a line across it. So if you want to demonstrate is then it's quite easy (cover the line with a finger). Conversely if you want to avoid the issue then don't put your fingers over the line (hence the much quoted; "you're holding it wrong"). However such spots exist on other phones too, they just aren't as clearly marked ;-)
"...Apple's attitude to the problem with their high-end device where style has prevailed over best-practice RF engineering."
If Apple had owned up to it whether saying it was a design flaw or a design decision, the flameage would not have been as intense. Granted saying design flaw would probably have been more expensive as people would then have expected them to FIX the design and retrofit it to all the devices already sold, but it would have reduced flameage.
Not spent any time in the field of RF design then?
At some wavelengths and in certain circumstances touching an antenna can result in an increased ground plane effect which might improve reception.
That's not true for UHF or microwave.
The issue here is that the finger bridges two different antennas creating a new hybrid metal/person/metal antenna that is severely compromised for any of its intended uses.
Wow, wouldn't have guessed. Holding ANY phone degrades the signal - I see it on my iphone 3gs + 4, also on my ancient nokia dumbphone and my wife's new nokia dumbphone.
And the bumper: it's there to prevent the antenna bridging, and works brilliantly. With my iphone 4, I can kill the connection most of the time by holding it tightly. With a case, the effect is minimal (no worse than the other phones anyway).
Can I get a large research grant for typing that please?
"no worse than the other phones anyway"
You people keep saying that even though it is totally and utterly wrong.
While all phones may have a reduced signal in certain circumstances, the iPhone 4 has a special, additional problem all of it's own. That is what this research is saying.
No one is going to give a grant to person who has difficulty comprehending basic information.
"And the bumper: it's there to prevent the antenna bridging"
No. It's sold as insurance against the 4's well documented reception problems not specifically to prevent "antenna bridging". Look like it doesn't work.
"then with the antenna actually in contact with a "thumb phantom" with the same dielectric properties as human skin."
So they didn't actually test it with an actual human thumb attached to an actual human person? How then can any reliable conclusions be reached? All they've demonstrated is antenna performance in an unnatural laboratory situation that assumes their replacement mimics all the variables of the real-life scenario.
They can say that the "phantom thumb" mimics the human thumb, but without a comparison performed in the same experiment how do they know? It's an assumption that may not be true.
It's quite a common ailment amongst fanboys.
No doubt someone will also attempt to explain how holding the precious while using it with no measurement equipment other than the reception bars is far superior to controlled conditions in a lab performed by an expert in the field.
Never mind guys.. Tell us again about the market cap..
Selective indeed. If you read what it says, the whole point of the experiment was to see what the difference a "bumper" made. Which they did not test with a real thumb or real hand or real person.
The test you are referring to was when the phone was held to demonstrated that it "reduced sensitivity" of the antenna. Which is not news to anyone, and wasn't the point of the experiment.
"if my iPhone 4 was 100 times less sensitive"
You forget that 100 times is 20dB, a big but not catastrophic difference to something like a mobile phone.
True that in free space it would represent a 10 time difference in distance, but in most mobile situations (e.g. in a city) you are pretty close to the base station and the phone can adjust its power to compensate, probably by over 20dB, so you see little effect on operation just a shorter battery life.
So you tend to get dropped calls when the network is busy and/or where you are further from the base station (but still in the nominal coverage zone).
One of the chacteristics of 3G/GSM phones is that they (and the base station) adjust the power required to the minimum necessary, to limit interference and save battery life. Faced with a poor antenna, the phone will just blast out more signal. It would only be in situations where the signal is already poor that you'd actually see problems, dropped calls, etc.
I think the conclusion was that even with the antenna detuning the iPhone 4 had better reception than the iPhone 3.
And if a bumper does not help then why not expose the antenna rather than sticking it just inside the plastic case like most smartphone do? Then iPhone 4 with a bumper is exactly like the iPhone 1-3 antenna placement wise.
My own experience with the iPhone 2 and iPhone 4 is that I get a little better reception with the iPhone 4. I use a bumper for glass protection but will probably remove it after a year or so when the phone isn't so shiny.
No real surprise, really.
Anyone who has messed around with radio antennas knows that you can receive some rather strange results. Even today's digital TV signals present some very interesting situations. Such as the orientation of a LCD monitor some feet away from either the TV or the antenna. It changes the reflected signal. And at marginal receptive times, the effectiveness of the antenna can be observed. Some have even claimed that getting up to take a break affects the signal. No doubt it can happen.
Touching the antenna does detune it. And being nearby can do so as well.
Surely this can affect any handheld device. You have a big bag of mostly water so near the antenna. And that can affect the signal.
Only an idiot would design an antenna that in normal use is being touched by the user. Holding it just so probably helps. But, it is a bad design decision. Would you buy a car that heads into the ditch if you do not hold the steering wheel just right?
er no, cars go straight ahead if you take your hands off the wheel (assuming the wheel was straight to begin with)
If your car is heading ditchwards, I'd take it to a garage ASAP and get it's alignment done quick-smart, because you're wearing your tyres unevenly, and could have them fail on you.
If your front-end alignment is ok, then it might be that you're experiencing the 'crown of the road'. Put simply, roads are not 'flat' but curved slightly, with the center slightly higher than the outside edges, so that water goes to the side, for drainage, reducing ponding.
Cars aren't designed to drift into the outside. Roads are designed to drift all uncontrolled objcts to the outside. Look up "camber" and you'll understand.
The better analogy is not buying a car that drifts to the outside of the road if the wheel isn't properly held, it's buying a car that drifts out because the wheel CANNOT be properly held.
Way back when Montgomery was chasing Rommel around the deserts of North Africa, the tanks had No. 19 sets which had an HF (High Frequency) main transmitter/receiver and a UHF transmitter/receiver compromising, I think, only one or two valves (tubes in North America) - the oscillator was also the 'power' amplifier, the other tube being the FM modulator. (See: < https://secure.wikimedia.org/wikipedia/en/wiki/Wireless_Set_No._19 >. The UHF unit is next to the power supply connector).
Apart from the tanks in the desert disrupting UHF transmissions in the UK (really), these UHF units could also be detuned off the operating frequency by grabbing the short antenna.
But I guess the Apple antenna specialists are more interested in re-inventing the wheel. Even square ones.
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