Previous 1 2 3 4 Next 49 Replies Latest reply: Sep 6, 2012 7:49 PM by diesel vdub
dbk9999 Level 1 Level 1
Since 4.1 has given us back the ability to use Field Test Mode, we can all check the numbers for ourselves. Up until now, I've only seen two sites that were able to do testing with these kinds of results instead of just the 0-5 bars. That isn't much. One reported up to a 24 decibel reduction in signal and the other said 20.

To activate field test mode, on your phone keypad enter:

3001#12345# and press the call button. You'll get an almost blank screen - it has a refresh button which doesn't seem to do anything. The numbers seem to change without doing anything with that button. In a few seconds, your antenna signal bars should turn into negative numbers (bigger negative numbers are worse signal). Here are how the numbers correspond to the bars on the iphones since they adjusted the formula in 4.0.1:

-51 to -76 = 5 bars
-76 to -87 = 4 bars
-87 to -98 = 3 bars
-98 to -107 = 2 bars
-107 to -121 = 1 bar

I believe only the iphone 4 can go that low and still make calls. Older phones can go to -113.

I do not know how quickly the numbers change when the signal changes. I know the bars have a built-in delay so this may as well. Some testing should clarify this.

Now maybe we can get a lot of tests, like this:

1. No case, iphone 4 setting on a table or desk to minimize interference. Write down the number.

2. Pick up the phone and hold it "wrong" (cover both sides of the plastic separator on the left side). Write down the number you get.

3. Put on the case and repeat the above tests.

Keep in mind that the numbers can suddenly change anyway. I don't know all the situations, but, for example, your phone could switch to a different tower. I also read someone say that the kind of network AT&T uses will have sudden fluctuations. I know I've seen the bars change without me doing anything with the phone. Using the field test mode today, I've seen the numbers suddenly jump 10 or more, though most of the time it tends to stay about the same.

So, when testing, multiple tests would be wise to separate the odd ones from what is normal. If you run, say, 5 tests like the first two on the list and usually lose 20 db, but one time you only lose 10 or lose 30 instead, that is probably a change that is in the network and should be discarded.

I'd like to see a lot of people testing to give a better idea of how much of a problem this is and how effective different cases are.

Macbook, Mac OS X (10.6.2)
Solved by viewfly on Sep 12, 2010 6:47 PM Solved
I've had the dBm working since the 3G. It carried over to each upgrade (non-JB iPhones, 3GS and now 4). So I've been looking at IP4 dBm's since July.

I've found it does depend where you start. Also, no need to do a unrealistic 'death grip', just a light grip or single finger in the 'sweet spot' will tell you the RF map of the SS band antenna.

1. When starting out at -90dBm or worse, I can hold the phone anyways I wish, with a normal grip and see no long as I don't touch or bridge the 1mm black gap at the lower left we all know. I can touch just above it, below it, or even place one finger above and another below, with no effect. Likewise touching the other black gaps has not effect in either dB's or data speeds.

But touching/bridging that 1mm black lower left gap will kill my data speeds and/or drop my signal by about 20 dB's, as others have found.

2. However, if I start at -78 dBm or better (-63, -51 dBm, etc), I found touching the lower left black band has NO effect on dBm's or data speeds. I haven't mapped carefully the area between -78 and -90. So it doesn't reduce 20 dBm al all. But from what I see above, -84dBm is still a sensitive signal area. This is the reason why some see no effect and other do not.

Can anyone else confirm this?

What this means for me is in a strong signal area (5 bars, maybe 4) I can hold the phone (normally) without any effect. For weaker signals, I can hold the phone normally, but must be careful not to touch directly the one black lower band. Touching or holding the SS band anywhere else has no effect.

A strong death grip is an unusual grip. I think squeezing that hard compresses your skin, increasing skin density and hence water area on the phone and has some effect....but mostly, the death grip involves strongly pressing part of the hand palm against the lower black band...and that is what kill the signal
Reply by Prabas on Sep 9, 2010 4:27 AM Helpful
-76 when holding normally (4 bars) (no case)
-91 when holding like an idiot (3 bars) (no case)

It's iPhone 4 16GB - made on Week 34
Reply by pogster on Sep 9, 2010 4:36 AM Helpful
-73 when laying flat on the table
-97 in idiot mode lol

To get to a lower value I'd have to be in a fringe area would I not? If so this test only applies to those located in poor reception areas.

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