Sunday, February 17, 2013

iPhone | iOS (4.1 and above) | Put phone in Field Test mode

As many may have already read, it is possible to put your phone into "Field Test" mode.  What does this do?  It allows you to see the true signal strength in number form as opposed to just the bars you always see that mean absolutely nothing, when it really comes down to it.

It is possible to follow these steps on any iPhone running iOs 4.1 or newer.  (My understanding is...) Any phone except the iPhone 3GS.

How to Temporarily Enter "Field Test" Mode

Follow the steps below to (temporarily) put your iPhone in Field Test mode, then I will explain what it all means.

  1. Dial *3001#12345#* into your phone's keypad.
  2. Hit “Call” and the Field Test mode app will launch.

The first thing you'll notice is that there is now a number where your signal bars used to be.  

The second thing you'll notice is that you are looking at a weird screen that has two lines on it.  These say something to the effect of: 

  • 1xEV-DO
  • 1x

Each has a (go-forward) arrow next to it.  If you click on the arrows you'll see a lot of technical stuff (pictured below).  However, your screen may look slightly different depending on the phone you have and the network you are on.  I am on Sprint and have an iPhone 5.

But the important part (at least to WE the users) is the number replacing the signal bars.

You can toggle between Bars and dBm number by tapping the number.

Unfortunately there is a problem here.  "What is that?" you may be asking.  If you hit your Home button, you leave "Field Test" mode and the bars return.  So let's fix this. Let's remain in "Field Test" mode indefinitely.

How to Remain in "Field Test" Mode Indefinitely

To remain in "Field Test" mode indefinitely... We are going to start from scratch, as if you have exited Field Test mode (by hitting the Home Button) and are back in regular mode.
  1. Dial *3001#12345#* into your phone's keypad.
  2. Hit “Call” and the Field Test mode app will launch.
  3. Now hold down the Power button until the “Slide to Power Off” message appears.
  4. Release the Power button
  5. Now Hold the Home button until the "Field Test" screen quits.
What you notice is that now your phone is back in Normal operating mode, but you can still see the true signal strength represented in Number form.

To return back to regular operating mode

To return your iPhone to normal operating mode once you have entered "Indefinite Field-Test Mode",  Just follow the instructions below.
  1. Dial *3001#12345#* into your phone's keypad (Just as before).
  2. Hit “Call” and the "Field Test" mode app will launch.
  3. Then hit the home button.  
    • This will close the Field Test app screen.  But it will also return your iPhone to regular operating mode.
The phone will remain in "Indefinite Field-Test Mode" even after restarting your iPhone (at least on mine), so this is not an option.  

What do the Numbers mean?

First you need to understand what the numbers mean. The number is a representation of dBm.
dBm = deciBels to the milliwatt. 
The numbers you see may look something like (-88) or (-105)

The numbers don’t follow a scale that makes much sense to normal people, but suffice it to say, (Thinking in negatives and positives where -100 is smaller than -70) the lower the number (in other words, the more negative) the worse the signal.  And the higher the number (less negative) the better.
  • Anything above -80 is good, and would be considered full bars   (i.e.: -79 thru -0)
  • Anything below -100 is bad, and would be considered few bars  (i.e.: -101 thru -120)

The purpose of this blog post was only to show you how to enter and remain in Field Test mode on your iPhone.  I honestly don't know what all of the tech jargon means on the Field Test Screen.

For a more detailed explanation of what the signal bars actually mean, visit the following website: