Check Your iPhone 4's Antenna Reception With Field Test Mode In iOS 4.1:

Irish Rose · ‎11-30-2008

Now you can put your iPhone into field test mode, which will allow to easily and precisely test your cell signal reception quality. You just need to follow these two easy steps:

• First, upgrade your iPhone 4—or any iPhone—to iOS 4.1.
• Dial *3001#12345#* into your phone.

Done. The signal bars will be replaced with a number (like -85). The more negative the number, the worse the signal is.

Example: -110 is worse than -85. Once activated, you can switch between signal bars and number by touching on the number.

Try the test mode now. Then use a finger to connect the two metal bands on the lower left corner, over the black plastic strip. That will short-circuit the magical gap and bring the phone's signal down quite significantly.

To get out of the field test mode, just hit the home button. [Thanks KTK1990!]

Story link found here.

Demetri70 · ‎06-18-2008

While in "field test mode" if you hold the power button for 5 seconds and then hit the home button you will ALWAYS have the db option and can tap it to bring the bars back...

Irish Rose · ‎11-30-2008

Here's a tip that will get you into the field test mode more quickly; put "Field Test" and the number to get into it, in your contacts list. Then when you want to do a true test of the reception in your area, just copy the number, and paste it into your iPhones key pad, and hit CALL...... Once this is done, you will be taken to the Test Field screen, which looks something like mine below. I found that my iPhone 4 gets better reception with a -69, than any of the Blackberry devices that I used in the past.

To get out of the Field Test screen, simply hit the HOME button on your iPhone.

Irish Rose · ‎11-30-2008

Demetri70 wrote:
While in "field test mode" if you hold the power button for 5 seconds and then hit the home button you will ALWAYS have the db option and can tap it to bring the bars back...

As soon as I hit the home button, I am automatically taken out of the Field Test screen.

Demetri70 · ‎06-18-2008

While in field test mode you need to force quit. Hold the top button until the slide to power off screen pops up (don't slide) just hold the home button. After that when you tap the bars you get the bd level again. This will stay there all the time unless you restore the phone.

Irish Rose · ‎11-30-2008

It worked for me that time. Thank you Demetri.

graphite07 · ‎10-16-2007

Irish Rose wrote:
Now you can put your iPhone into field test mode, which will allow to easily and precisely test your cell signal reception quality. You just need to follow these two easy steps:

• First, upgrade your iPhone 4—or any iPhone—to iOS 4.1.
• Dial *3001#12345#* into your phone.

Done. The signal bars will be replaced with a number (like -85). The more negative the number, the worse the signal is.

Example: -110 is worse than -85. Once activated, you can switch between signal bars and number by touching on the number.

Try the test mode now. Then use a finger to connect the two metal bands on the lower left corner, over the black plastic strip. That will short-circuit the magical gap and bring the phone's signal down quite significantly.
To get out of the field test mode, just hit the home button. [Thanks KTK1990!]

Story link found here.

hit the home button after. i get 97 my singal sucks,

MC_Hammer · ‎06-26-2010

Is there a magic number threshold that when reached makes the calls drop? I've only had one dropped call but never see more than 2-3 bars. I'm seeing -92 through -120.

DonSchwarz · ‎03-30-2006

Is there a way to turn it off without a restore? Also where can one find other goodies like this one?

GeekBoy · ‎11-06-2008

MC_Hammer wrote:
Is there a magic number threshold that when reached makes the calls drop? I've only had one dropped call but never see more than 2-3 bars. I'm seeing -92 through -120.

I seem to recall that with the iPhone 3G, the word was that if the signal hit about -115 or worse, you were at risk of dropping calls. I know just yesterday that I was on a call in a "known bad reception area" and my signal meter was reading about -117. That call was breaking up so bad that it was not understandable, but the call didn't drop. Once I left the bad area the signal jumped to -98 and within a second the call was bad to good quality.

jjforau · ‎11-16-2007

Very interesting results. I have an otterbox on my iPhone 4 and when I squeeze the bottom where those problems areas are, my signal just fell from -83 to -107 within 10 seconds. When I placed the phone on my desk, it went back to -83.

UNSC_REACH · ‎07-16-2010

I just want to put this out there: Once you "force quit" the field test, the bars/db option will only be removable with a non-backup restore.

I've restored then restored from backup many times and it didnt work. Also, when I had a 3GS, I bought a iPhone 4 - I did a backup restore and the db's came on my new iPhone 4, it was running iOS 4.0. So the backup carries the db option. So once you back your phone up with the db's, you cannot go back whithout using older backup, or just starting from scratch.

Not that I care, personally I love the db's, just wanted to make everyone aware.

cousintim · ‎05-24-2005

Great tip. Thank you.

johninsj · ‎07-07-2010

Nice...

At work... -65 with case on (simple no name green rubbery case thingie) gripping or ungripping

removed case, no chage - gripping or ungripping

tried licking finger/palm first, no change in signal

buried phone in both hands so only top corner was visible... no change

So, in a great signal area, there is no impact.

Will try at home later, where signal is very marginal

GeekBoy · ‎11-06-2008

How about immersing the bottom half in a glass of water and tring it for us?

johninsj · ‎07-07-2010

GeekBoy wrote:
How about immersing the bottom half in a glass of water and tring it for us?

Yeah. You gonna buy the replacement phone?

MC_Hammer · ‎06-26-2010

UNSC_REACH wrote:
I just want to put this out there: Once you "force quit" the field test, the bars/db option will only be removable with a non-backup restore.

I've restored then restored from backup many times and it didnt work. Also, when I had a 3GS, I bought a iPhone 4 - I did a backup restore and the db's came on my new iPhone 4, it was running iOS 4.0. So the backup carries the db option. So once you back your phone up with the db's, you cannot go back whithout using older backup, or just starting from scratch.

Not that I care, personally I love the db's, just wanted to make everyone aware.

Interesting, so I assume when 4.2 is pushed that will bring back the bars only? Otherwise you have to restore from a previous backup and lose pictures etc?

user3977 · ‎10-25-2005

i know this may be out there as far as this goes but i had 3 days left in my warranty for my 3gs and went to apple with a battery issue. they said that the phone is in warranty but due to the fact that the bars were gone and the signal strength is showing i did some sort of jail break on my phone and would not deal with the phone since it was jail broken. i tried to explain to them that it has never been jail broken and that i can easily put the bars on there. it is just showing the signal strength. well that was no good. they were sticking that it was hacked somehow and voided the warranty. so just incase anyone plans to take phone in to apple for any reason make sure that you have bars showing.

UNSC_REACH · ‎07-16-2010

MC_Hammer, I've had the db's for a while now, several updates. I've even updated to 4.2 beta, same. I dont think there is any way to get rid of them otherwise.

UNSC_REACH · ‎07-16-2010

user3977, great point! I've been to Apple more then once, with the db's showing but forgot about it and they didnt notice. But I can easily see how inexperienced genius bar agents could think that. Kudos for bringing that up!

Demetri70 · ‎06-18-2008

That's correct it's saved in the backups. I had the db's on my iPhone 3G for two years and when I got my iPhone 4 I used my backup files to set it up and still kept the db's. Apple removed the option in iOS4 and you couldn't get in field test mode on a iPhone running 4.0, when I had a problem with my iP4 and set it up as new I lost the db's and couldn't add them back until 4.1 came out when the field test option returned. As far as Applecare it is not a Jailbrake and doesn't modify Apple's OS, both my Apple Store and local AT&T store were the ones who showed me how to do it. I also had my iP4 replaced at a Apple store with the db's on it (was replaced due to shutting down by itself 4-5 times a week)..

MC_Hammer · ‎06-26-2010

I'd rather have the bars most of the time, so I did a full reset. Took a few minutes to put everything back, but it wasn't a big deal.

millertimer · ‎06-09-2010

Or you could just touch the numbers and the bars will show. Just leave it that way.

MC_Hammer · ‎06-26-2010

millertimer wrote:
Or you could just touch the numbers and the bars will show. Just leave it that way.

Mine kept reverting back to field test mode and I got tired of it.

Irish Rose · ‎11-30-2008

MC_Hammer wrote:
millertimer wrote:
Or you could just touch the numbers and the bars will show. Just leave it that way.
Mine kept reverting back to field test mode and I got tired of it.

Not sure why it kept doing this for you. It worked for me immediately after holding the power key for 5 seconds, then pressing the home key. I am now able to go back and forth between the bars and the number reading without a problem.

Irish Rose · ‎11-30-2008

MC_Hammer wrote:
I'd rather have the bars most of the time, so I did a full reset. Took a few minutes to put everything back, but it wasn't a big deal.

I'm the exact opposite, as I feel that the best and most reliable way to measure the reception on any phone is with the numbers, therefore I have my iPhone set to the numbers most of the time.

MC_Hammer · ‎06-26-2010

Irish Rose wrote:

MC_Hammer wrote:
I'd rather have the bars most of the time, so I did a full reset. Took a few minutes to put everything back, but it wasn't a big deal.
I'm the exact opposite, as I feel that the best and most reliable way to measure the reception on any phone is with the numbers, therefore I have my iPhone set to the numbers most of the time.

I agree 100%, for some reason it was bugging me and it kept reverting back to the db on its own, so that's why I did a reset.