Field Test for iPhone Signal Strength Returns in iOS 4.1

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When Apple released iOS 4.1 for iPhone Wednesday, the company once again included a utility that allows you to measure your signal strength on your device, a utility that that had been available before the release of iOS 4, but was not included when iOS 4 was introduced earlier this year.

The utility is called Field Test, and it is accessed by dialing *3001#12345#* (followed by the “Call” button). When you do that, a blank “page” launches with a title bar that reads “Field Test,” along with a Refresh button, as you can see in the image below. The Field Test part is that your signal bars will be replaced with a negative number that measures signal strength as expressed in decibels of noise in the signal.

To that end, the higher the number, the stronger the signal. -80db would represent a stronger signal than -90db, and -102db would be worse still (for instance, this reporter has particularly foul coverage at his office). TMO staff around the country found signal strengths ranging from -82db to about -120db, with any number lower than that representing little or no practical signal.

From user posts at Gizmodo, which first noted the return of Field Test, any Field Test near -70db represents something close to full signal strength. One staff member with an AT&T 3G Microcell got a measurement of -67db from one meter away from his microcell.

Pressing the Home button on your iPhone will end the Field Test and return your display to normal. Locking your phone (or allowing it to self-lock) with the Field Test still running will leave the Field Test numbers in your menu bar until you come back and quit the app via the Home button.

Field Test Results

Field Test in iOS 4.1 on iPhone 4 in area with poor coverage

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25 Comments Leave Your Own

fix

“To that end, the higher the number, the stronger the signal.”

You meant to say, “To that end, the LOWER the number, the stronger the signal.”

Yaymath

You meant to say, ?To that end, the LOWER the number, the stronger the signal.?

This is your friendly neighborhood math teacher here to remind you that a more negative number is less than a less negative number.

e.g. -90 < -80.

In other words, the original statement is correct.

Unfix

No he didn’t, since they’re negative numbers. The higher the number, the stronger the signal. Idiot.

Kevin

?To that end, the higher the number, the stronger the signal.?
You meant to say, ?To that end, the LOWER the number, the stronger the signal.?

Actually, the way it is written in the article is correct.  A smaller (magnitude) negative number is larger than a larger (magnitude) negative number.  You know, kind of like when your third-grade teacher taught the class that.

no fix

fix - The author does not mean the LOWER number. Since it is a negative number, the closer the displayed number is to zero is best. Closer to zero = higher number.

anonymous

No, he meant what he wrote.
Remember these are NEGATIVE numbers.
-90 is bigger/higher than -120

TechGuy

?To that end, the higher the number, the stronger the signal.?

You meant to say, ?To that end, the LOWER the number, the stronger the signal.?

The author is correct.  The higher the number, the stronger the signal.  It’s basic mathematics: -80 is a higher number than -90.

Mike D.

You meant to say, ?To that end, the LOWER the number, the stronger the signal.?

Actually, the negative sign would mean that -80db is a HIGHER number than -90db.

So, the text is fine as it stands.  When the authors are right, let them be right.

Joe Blowe

WTF?!?!?  Are you guys seriously STILL arguing about the higher/lower number statement.  Geez, you have no life.  LOL smile

MeAndYou

WTF?!?!?  Are you guys seriously STILL arguing about the higher/lower number statement.  Geez, you have no life.  LOL smile

Check the timestamps, idiot. Several people started to respond to the original comment at the same time.  What a troll.

el

Ok….number line…..closer to 0 from the negative side of the line the higher the signal. 3….2…..1…..0…..-1…...-2…...-3

Joe Blowe

Yeah, twenty minutes of their lives wasted.

Joe Blowe

Joe *** telling time ***  when the big hand is on the…...

IO

Let’s dumb it down and put it another way. If it is -20 degrees then it is warmer than if it were -30 degrees. Duh!

FranSaysUGuysAreRetads

-99 is less than -100, but Finkle is Einhorn and Einhorn is Finkle so -100 could be less than -99 too

Yanik Cr?peau

Just run the test in downtown Montr?al QC. I had -65 dB.

I am not very surprised by this excellent result. I travel frequently in Canada, the USA and Europe (France, Spain, Italy, UK…) and it is obvious than the coverage is much better outside the USA than places like downtown San Francisco where I have worked for 4 or 5 years.

One morning, in my Outer Sunset (part of San Francisco near the Pacific ocean) I have launched the Google Map application and tried to set my position on the map. The only way to achieve that was to use the 3G cell towers triangulation since I was indoor (no GPS avail. ) and had switched off the Wifi. For a brief moment, my location was the “nearest” 3G cell tower (aka the cell tower servicing my iPhone) and it was in Daly City, 7 miles (or 12 km) from the place where I was actually. At that time, AT&T had only 4 or 5 cell towers with 3G capabilities and servicing the entire City. When the N-Judah street car was leaving the subway tunnel, everyone in the train equipped with a 3G compliant device was trying to hook up with the 3G network at the exact same time; making the tower hardware crashing and shutting down any cell phone conversation in the neiborhood. AT&T fixed that issue later on, in May 2009.

The software running in the cell towers is very buggy and crashes pretty often when the data transfer load reaches a certain point.

The miracle solution to all these problems: add more towers. Smaller cells makes the 3G network stronger.

MeAndYou

This thread has gone to shit

YouGuysAreIdiots

-99 is less than -100, but Finkle is Einhorn and Einhorn is Finkle so -100 could be less than -99 too

Idiot, its more than. Did you not learn from the previous posts?

Scott

fix,
The first statement is correct.
?To that end, the higher the number, the stronger the signal.?
-67 dB is higher (bigger, larger) than -113 dB
If your checking account is $-67 than you are better off than it being $-113.

MacKeeper_fan_Mod

How to remove field test mode.
If you were like me an turned on the field test mode using the power button hold and then the home button there is hope. It will come at a cost though.

You will need to navigate to: Settings/General/Reset/Reset All Setings.

This will make you have to set up your phones settings again (ring, pas code, email signature, etc.) but will turn off the switching.

Hope this help!

RonMacGuy

Well, I did enjoy the “Finkle is Einhorn and Einhorn is Finkle” movie quote from Ace Ventura.  Funny stuff.  Frankly I am still trying to figure out what the big deal is about a bigger negative number vs. just looking at the freaking bars on the blasted phone!!  But that’s just me!!

filmfrog

I got -67 sitting in my car in the parking lot of a Staples here in Toronto. I’m on the new Bell/Telus HSPA network.

Bryan Chaffin

I axed the profanity-ladened posts.

And I am jealous of our Canadian commenters with the awesome signal strengths! smile

GreatGazoo

Getting back to measured signal strengths, we have an AT&T microcell in our office (without the microcell, cell reception is very bad).  iOS4.1 Field Test reports -63dB at the corner of our office farthest away from the microcell (about 30 feet away with 3 interior walls in the way.  This means the microcell does what it’s supposed to rather well.

spudgeek

Please everyone - calm down!
You will receive less reception from your readers if you continue to increase your negativity smile

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