I thought the whole steel band was the antenna?

[Mjmar]

The iPhone 4 antenna confuses me. If the whole band acts as the antenna then why do the calls drop only when you hold the phone in the bottom left corner? And how do radio waves travel through steel anyway? I wanna know so I can hold the phone the right way without loosing service.

 

[quagmire]

The iPhone 4 antenna confuses me. If the whole band acts as the antenna then why do the calls drop only when you hold the phone in the bottom left corner? And how do radio waves travel through steel anyway? I wanna know so I can hold the phone the right way without loosing service.

The issue is bridging between the two antennas. The steel band below the left hand seam is the cell antenna. Above it is the WiFi/BT/GPS antenna. The rubber seam is to keep those antennas separate. When your finger/hand touches both in that area, it creates a bridge causing what I would imagine some kind of interference or if it is software related, tricking the software to think the signal is crap.

That is what I have observed in videos and my own tests. Touching the rubber seam itself does nothing to my signal nor does just touching the cell antenna part below the seam.

 

[saving107]

quagmire is correct, and their is a more in-dept article I saw earlier today that explains what's going on, I'll see if I could find. Also, because of radiation testing, the FCC requires that all phone manufacturers place the Radios on the lower portion of every phone (keep it further away from the brain), so this is not just an iPhone issue.

 

[Mjmar]

The issue is bridging between the two antennas. The steel band below the left hand seam is the cell antenna. Above it is the WiFi/BT/GPS antenna. The rubber seam is to keep those antennas separate. When your finger/hand touches both in that area, it creates a bridge causing what I would imagine some kind of interference or if it is software related, tricking the software to think the signal is crap.

That is what I have observed in videos and my own tests. Touching the rubber seam itself does nothing to my signal nor does just touching the cell antenna part below the seam.

So the iPhone 4's antenna IS the steel band, whereas the older iPhones antennas were not visible?

 

[quagmire]

So the iPhone 4's antenna IS the steel band, whereas the older iPhones antennas were not visible?

Correct. The iPhone 3G and 3GS had them under the plastic backing and the original under the black strip at the bottom.

 

[Mjmar]

Correct. The iPhone 3G and 3GS had them under the plastic backing and the original under the black strip at the bottom.

IDK about you but that seems unsafe to me.

 

[Setter Guy]

IDK about you but that seems unsafe to me.

Agreed. File the iPhone 4 with horseless carriages, dirigibles, and microwave ovens.

 

[Errk!]

The issue is bridging between the two antennas. The steel band below the left hand seam is the cell antenna. Above it is the WiFi/BT/GPS antenna. The rubber seam is to keep those antennas separate. When your finger/hand touches both in that area, it creates a bridge causing what I would imagine some kind of interference or if it is software related, tricking the software to think the signal is crap.

That is what I have observed in videos and my own tests. Touching the rubber seam itself does nothing to my signal nor does just touching the cell antenna part below the seam.

Great explanation - thanks. I was confused too.

If this is the case, shouldn't we be having the same problems if you hold it so that, say, your thumb is on the left side and your other fingers on the right? Does it only matter if one finger is touching both sides at one time? And if so, why would that be?

 

[Gigamaster89]

If for whatever reason you decide to put your hand on the top where the bands connect, you would have the same problem?

 

[quagmire]

Great explanation - thanks. I was confused too.

If this is the case, shouldn't we be having the same problems if you hold it so that, say, your thumb is on the left side and your other fingers on the right? Does it only matter if one finger is touching both sides at one time? And if so, why would that be?

Frankly, I have no idea why that is the case. Touching the two separate bands on the opposite side vs joining them by that seam. I am no engineer, so I am far from an expert on this. But, this would be my best guess( out of the blue, etc). As we all know and has been pointed out, how can stainless steel be the antenna while at the same time, it disturbs the signals( why the original iPhone and iPad 3G has that black strip). What I think Apple engineers did was take that physics and used it for their advantage. Where the whole outer band absorbs the signals and some how directs them to the main antennas.

And as pointed out in step 12 of iFixit's iPhone 4 teardown, the cell antenna at least( they never pointed out the WiFi/GPS/BT antenna) is where the left seam is. So the interference is the strongest there causing the issue. Where touching it on the opposite sides doesn't cause much of an issue because you're not near the actual antenna.

Thinking of this guess, maybe it isn't a bridging problem. It's just you're blocking the actual antenna from getting the signal. This could explain why the problem still happens even with WiFi/BT/GPS all turned off. Again, I have no idea how Apple engineered the iPhone and antenna system nor am I an engineer at all myself. So I can very well be 100% wrong.

If for whatever reason you decide to put your hand on the top where the bands connect, you would have the same problem?

I tried that and it doesn't affect WiFi or cell reception. Even when I am far away from the router( using the theory of the issue is only present when the signal isn't that great).

 

[Uabcar]

So the hand bridging the two antennas issue makes perfect sense- and explains why using a case seems to resolve the problem.

What does not make sense is the argument that other phones have the same problem. I don't see how this could be an issue with the 3gs for example. No metal to 'short out'. I'm sure the added mass of your hand - to transmit though- would impact the signal to some minor degree on all phones.

 

[Amnesia87]

Frankly, I have no idea why that is the case. Touching the two separate bands on the opposite side vs joining them by that seam. I am no engineer, so I am far from an expert on this. But, this would be my best guess( out of the blue, etc). As we all know and has been pointed out, how can stainless steel be the antenna while at the same time, it disturbs the signals( why the original iPhone and iPad 3G has that black strip). What I think Apple engineers did was take that physics and used it for their advantage. Where the whole outer band absorbs the signals and some how directs them to the main antennas.

And as pointed out in step 12 of iFixit's iPhone 4 teardown, the cell antenna at least( they never pointed out the WiFi/GPS/BT antenna) is where the left seam is. So the interference is the strongest there causing the issue. Where touching it on the opposite sides doesn't cause much of an issue because you're not near the actual antenna.

Thinking of this guess, maybe it isn't a bridging problem. It's just you're blocking the actual antenna from getting the signal. This could explain why the problem still happens even with WiFi/BT/GPS all turned off. Again, I have no idea how Apple engineered the iPhone and antenna system nor am I an engineer at all myself. So I can very well be 100% wrong.



I tried that and it doesn't affect WiFi or cell reception. Even when I am far away from the router( using the theory of the issue is only present when the signal isn't that great).

The reason it doesn't cause nearly as big a problem when in your right hand is while yes your hand is technically still bridging the signal. We are very bad conductors, lots of resistance, so when it's the palm of your hand it much easier for the signal to hop that 2-3mm to get from one antenna to another, going across your entire hand is a much smaller issue, most of the signal is lost to resistance.

 

[quagmire]

So the hand bridging the two antennas issue makes perfect sense- and explains why using a case seems to resolve the problem.

What does not make sense is the argument that other phones have the same problem. I don't see how this could be an issue with the 3gs for example. No metal to 'short out'. I'm sure the added mass of your hand - to transmit though- would impact the signal to some minor degree on all phones.

That is why I put the following in my above post.

Thinking of this guess, maybe it isn't a bridging problem. It's just you're blocking the actual antenna from getting the signal. This could explain why the problem still happens even with WiFi/BT/GPS all turned off. Again, I have no idea how Apple engineered the iPhone and antenna system nor am I an engineer at all myself. So I can very well be 100% wrong.

And as that states, I could very well be 100% wrong since I am no engineer.

The reason it doesn't cause nearly as big a problem when in your right hand is while yes your hand is technically still bridging the signal. We are very bad conductors, lots of resistance, so when it's the palm of your hand it much easier for the signal to hop that 2-3mm to get from one antenna to another, going across your entire hand is a much smaller issue, most of the signal is lost to resistance.

That makes sense....

 

[saving107]

here is the article I spoke of.
http://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-antennas.html

here are some highlights from the article, but its worth reading the whole thing:

The problem is that humans have their hands below their ears, so the most natural position for the hand is covering the antenna. This can't be a good design decision, can it? How can we be stuck with this conundrum? It's the FCC's fault.

You see, when the FCC tests are run, the head is required to be in the vicinity of the phone. But, the hand is not!! And the FCC's tests are not the only tests that must be passed by a candidate product. AT&T has their own requirements for devices put on their network, and antenna efficiency is one of them. I know because I have designed quad-band GSM antennas for the AT&T network. The AT&T test similarly does not require the hand to be on the phone.

So, naturally, the design evolved to meet requirements - and efficient transmission and reception while being held by a human hand are simply not design requirements!

The iPhone 4 has two symmetrical slots in the stainless frame. If you short these slots, or cover them with your hand, the antenna performance will suffer (see this video I found on YouTube). There is no way around this, it's a design compromise that is forced by the requirements of the FCC, AT&T, Apple's marketing department and Apple's industrial designers, to name a few.