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How to access your phone's signal meter

As you might have noticed the conventional 'signal bar' meter isn't really an accurate representation of how good your signal is. The normal meter (although fine for the average phone user) often differs between phone models, differs between base reference levels (what we consider 1 bar), and really only describes how much total signal your phone is receiving - no indication of quality.

So to give us a more accurate readout most phones already have the capacity to display signal in an absolute measure. In telecommunications this absolute measure is called dBm. It measures your received signal level in comparison to 1mW of energy - ie 0dBm = 1mW. Now because phones deal in levels much smaller than 1mW, we often see our dBm readout expressed in negative values. So when reading your signal meter it is important to remember -60dBm is greater than -70dBm ..the closer to zero we are, the better.

Here's a quick diagram that should allow you to convert bars into dBm.

If I've confused you, all you need to remember is the smaller the number the better. So without any further rambling here are the codes for your phone.

Phone Engineering Menus

Please scroll down to the applicable model phone.

Apple iPhone 3G/3GS/4/4S/5

Dial *3001#12345#* and press Call.
This is called field test mode. On 3G/3GS you can toggle between 'bars' and dBm any time by pressing the bars (once the code has been entered).

What frequency is my iPhone using?

This is important step for Optus and other networks that operate on multiple bands when selecting an antenna.
Dial *3001#12345#* and press Call.
Select UMTS Cell Environment
Select UMTS RR Info
Select Downlink Frequency
This will give you a channel number, followed by some other numbers in brackets. The channel numbers correspond accordingly:
850MHz: 4357 - 4458
900MHz: 2937 - 3088
2100MHz: 10562 - 10838

Android-based Phones

Go to: Menu -> About Phone -> Status
This will give a readout in dBm.
Dial *#*#4636#*#* for a full engineering menu.

To show what frequency your phone is operating on (ie 850MHz, 900MHz, etc) and for a fast updating dBm meter use the following code:
Dial *#0011# and look for the RSCP for the signal power and ECIO for the signal quality.

ZTE/Telstra Manufactured Phones

Dial *983*3641#
To turn off dial *983*3640# or hold the hangup button.
This works for most Telstra handsets, but might not work for all.

Blackberry Devices

Hold down the ALT key and type the letters NMLL
This will convert 'bars' into dBm. To toggle back to bars, repeat the process.