iPhone 3G Hardware Design Flaw?

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Level 1

118 points

iPhone 3G Hardware Design Flaw?

Mentioned elsewhere in another thread, but thought it worth starting this one specifically on this one point.

Was comparing actual reception strength (test mode) with a friends Nokia on 3G today and no matter how he held his phone, it showed the same signal strength i.e. actual dBms, NOT bars.

On the iPhone 3G with it held by the sides with two fingers, the iPhone actually showed 2dBms higher than the Nokia, but hold it as you would when making a call, ie with your palm covering the bottom of the phone (where the antenna is!!) and lo-and-behold, the signal strength drops by 12dBm and more.

I've just tried it on 2G and the effect is exactly the same. I'm in a very strong 2G area, so mine drops from -73 to -87 when you hold the phone as designed, meaning that it isn't noticeable in practice.

But if you happen to be in an area where it's -97 say, and THEN you hold it normally and it drops to -109, the effect is going to be to kill off the call.

Seems to me like a very serious design flaw in the iPhone 3G that isn't going to be fixed by firmware updates.

Anyone else see this effect too? Maybe if / when you're in an area where your calls aren't good, try holding the phone by the sides so the back of it is uncovered and see if the performance is any better?

I realise this is a very, very subjective test, but it could be the explanation of all the reception problems. Can't see a solution though even if it is, as it means that every iPhone 3G has to be recalled and replaced with a completely redesigned one.

And the chances of Apple doing that are?

Windows XP

Posted on Oct 6, 2008 10:17 AM

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Answer 1

gumsie

Level 4

2,179 points

Oct 6, 2008 10:44 AM in response to AVRHack

Don't really see how that's a design flaw. I have about 4 phones and they all run out of signal at different points in the basement of one of the buildings I work in. So different environments/obstructions affect each differently.

My phone seems to be problem free but I do see your point of view.

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Answer 2

AVRHack Author

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118 points

Oct 6, 2008 10:49 AM in response to gumsie

Sorry but I don't think you do see my point-of-view. Naturally buildings etc. obstruct the signal, BUT IT SHOULDN'T LOSE 12dBm JUST BY BEING HELD NORMALLY as you would for every single call.

That's the key point - not whether you're in a basement etc.

And my phone's pretty good too in a strong signal area - presumably where you are - but in a less-good area where a Nokia is still spot on, the iPhone goes to pieces.

Which is exactly what you would expect if HOLDING the thing NORMALLY causes 12dBm of signal loss.......

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Answer 3

gumsie

Level 4

2,179 points

Oct 6, 2008 10:51 AM in response to AVRHack

Mine doesn't suffer like yours does so I would say there is something else amiss. A design flaw suggests something that will affect all devices of the type.

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Answer 4

AVRHack Author

Level 1

118 points

Oct 6, 2008 10:59 AM in response to gumsie

Now that's interesting.

Are you saying yours doesn't suffer from poor reception in certain areas, or that yours doesn't drop 12-15 dBm on the signal strength when you hold it "normally" as opposed to with two fingers on the side from the front?

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Answer 5

gumsie

Level 4

2,179 points

Oct 6, 2008 11:06 AM in response to AVRHack

Oh no, I get reception issues like other phones but no degradation when I change the holding position.

Gonna try it again................

Update. I get a 2db drop max, but it doesn't happen every time, sometimes-more often than not there is no change.

Message was edited by: gumsie

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Answer 6

AVRHack Author

Level 1

118 points

Oct 6, 2008 11:18 AM in response to gumsie

Well that's very, very strange indeed. Now we're maybe getting somewhere.

Perhaps the problem is with people who's hands are super-absorbent 🙂 And I'm one of the ones who's are 😟

Seriously though, given gumsie's very different result from mine, I can't think of another plausible explanation other than that one - why else would my phone very reliably lose signal when I hold it normally, yet gumsie's doesn't?

Interested to see anyone else's test of this too so we can get a better 'sample size'

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Answer 7

gumsie

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2,179 points

Oct 6, 2008 11:20 AM in response to AVRHack

Bear in mind we don't know how accurate the field test is.

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Answer 8

AVRHack Author

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118 points

Oct 6, 2008 11:21 AM in response to gumsie

gumsie - do me a favour so we're sure we're doing the same thing.

Hold your phone with your left hand, middle (long) finger on the top and thumb on the bottom. Read the dBms.

Then cup your right hand around the back of the phone at the bottom, as you would when making a call. Check the dBms again.

In my case it's a minimum of 12dBm drop - easily enough to kill a call in a less-than-excellent signal area.

Are you sure yours is only 2dBm between these two?

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Answer 9

gumsie

Level 4

2,179 points

Oct 6, 2008 11:26 AM in response to AVRHack

Hold on then.

This is gonna kill you.
Right, first reading -85 dbMs
Changing position went down to -83, then 79, then momentarily 77 before..............................rising to -91!

Message was edited by: gumsie

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Answer 10

AVRHack Author

Level 1

118 points

Oct 6, 2008 11:36 AM in response to gumsie

Ahhhhhhhh!!!

But it's a NEGATIVE number, so the smaller it is the HIGHER the strength.

So -91 dBm is 6 dBm WORSE than -85 dBm.

Still nowhere near the drop I'm seeing, but a very significant drop nontheless.

When the iPhone was tested in the labs recently (see other post on that subject!) the tester concluded it had a 2dBm disadvantage over the Nokia it was compared to - not ideal but not the end of the world.

But 6 dBm for you and a whopping 12 - 15 dBm down for me IS a a HUGE deal.

***EDIT***

Stranger and stranger...... Now I'm still sitting in exactly the same place, same phone, same cell tower (the only one remotely near me!!) and now the difference is "only" 4dBm.

Same test, same phone, same hand, same cell tower, erm, er, eh? It's now dark outside? Are we going to get into all this ham radio atmospherics now? 🙂

I thought that was only for long-wave signals!!! LOL

Message was edited by: AVRHack

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Answer 11

gumsie

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2,179 points

Oct 6, 2008 11:32 AM in response to AVRHack

A significant difference then. One that I confess I don't notice as any problems I did have ceased after the 2.1 update.

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Answer 12

klopus

Level 1

30 points

Oct 6, 2008 5:00 PM in response to AVRHack

I think it applies to most slim phones with a antenna at the bottom where a lot of radio components have to be crammed together. My previous Samsung Blackjack 3G reception also fluctuated depending upon where you hold it. In fact its User's Manual explicitly advised not to obstruct bottom with fingers.

My iPhone 3G specimen doesn't suffer from any common on this forum problems including weak reception, dropped called, etc. Fluctuations with signal depending upon how you hold the phone are only noticeable in the areas of the very weak coverage which I don't experience a lot. So most of the time I just don't care how I hold the phone.

Message was edited by: klopus

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Answer 13

Oct 6, 2008 5:08 PM in response to AVRHack

hey just thought that i would test this out too and i did your test and i went from -75 to -99. thats a pretty big difference.

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Answer 14

gumsie

Level 4

2,179 points

Oct 7, 2008 12:38 AM in response to AVRHack

You think this could help perhaps?;

http://www.daydeal.com/product.php?productid=3761

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Answer 15

taltal

Level 1

24 points

Oct 7, 2008 1:34 AM in response to AVRHack

Thanks for bringing this up, AVRHack. I can only agree to what you write. I see the same drastic changes in reception depending on how I hold the iPhone 3G.

I have some more experiences to add:

1. Since 2.1, the display of bars and dbm in field test has become more "elastic" - meaning that there is a lag of a couple of seconds until you see the changes. so one must hold the iphone in the new position for a couple of seconds to notice the change.

2. dbm values change drastically according to the position you hold your hand in - but it changes more drastically from lower values (e.g. -67 to -89 dbm), but less from higher ones (e.g. -101 to -113 dbm).

As you write, AVRHack, you can't see this effect on your Nokia, so this points us to this being an iPhone specific issue.

I really wonder whether there are different iPhone 3Gs that show the effect on the *same frequency* while others don't. (I am curious whether this effect is especially strong on the 1.9 and 2.1 Mhz networks (which T-Mobile Germany uses).)

cheers

tal

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