Most of the iPhones and Android smartphones have four or five bars for network signal strength. Some of them even have three bars in the notification bar. But the number of bars is not an accurate measurement for the calculation of signal strength. To get the precise measurement of network strength, we use the field test mode.
In this article, you will know all about the field test mode and how to check the network signal strength in iPhones and Android smartphones.
How to access the Field Test Mode?
You must follow some necessary steps before accessing the field test mode. The important steps are as follows:
- Go to Settings and click on Wi-Fi. Turn off the Wi-Fi.
- Open Settings, click on Cellular. Now, you will see Enable LTE option. Turn off the LTE.
What is Field Test Mode?
Field Test Mode is a pre-installed software application on mobile phones. It provides you with all types of technical details and statistics of the cellular network. This helps you in understanding the current situation of the phone network and also to run hardware tests on mobile, if necessary.
Signal strength is measured in dBm. dBm is defined as the power ratio in decibels of the radio power per one milli-watt of energy. The value is always in negative. It ranges from -40 to -130 where -40 means very strong signal strength and -130 means dead or very poor signal strength.
How to Enable Field Test Mode in iPhone?
Open the Phone app on your iPhone. Dial 3001#12345# on your numeric keypad then press Call. This procedure will activate the Field Test Mode. You will notice a signal strength indicator on the upper left-hand corner of your screen. The phone bars have converted into numbers. The number can be anywhere between -40 to -130. If the number displayed on your notification bar is -50, then it is a good signal strength. The smaller the number, the better will be the network strength. To exit the field test mode, simply press the Home button. You will get back to the iPhone’s home screen with bars for the network signal.
How to Keep Numerical Display in iPhone?
It is possible to permanently keep the number to be displayed instead of bars for signal strength. Open the Phone app in your iPhone. Dial 3001#12345# on your numeric keypad then press Call. This procedure will activate the Field Test Mode. The number will be displayed. Now, hold down the Power button until you see the “Slide to power off” option. Do not power off your iPhone. Press down on the Home button until the phone app closes and you return to your home screen. The numerical display of signal strength will always be displayed.
If you wish to return to the default network bars permanently, then, dial 3001#12345# on your phone app. Press Call. Now, press the Home button once. The default network bars will be displayed.
Network Strength
3G Signal (RSSI):
| High | -50 to -75 dBm |
| Medium | -76 to -90 dBm |
| Low | -91 to -100 dBm |
| Poor | -101 to -120 dBm |
4G (LTE) Signal (RSRP):
| Very High | -75 to -88 dBm |
| High | -89 to -96 dBm |
| Medium | -97 to -105 dBm |
| Low | -106 to -112 dBm |
| Poor | -113 to -125 dBm |
What Frequency is my iPhone using?
Your iPhone displays 4G or 3G symbol to tell you about its internet speed. However, it does not tell you about its current frequency band. If your iPhone is connected to 4G (LTE), then enter the Field Test Mode. Select “Serving Cell Info”. A list of options will be displayed. The band number will be next to the “Frequency Band Indicator”.
| Band | Frequency |
| 3 | 1800 MHz |
| 5 | 850 MHz |
| 7 | 2600 MHz |
| 8 | 900 MHz |
| 28 | 700 MHz |
| 40 | 2300 MHz |
If your iPhone is connected to 3G (HSPA), then enter the Field Test Mode. Select “UMTS Cell Environment”. Now, select “UMTS RR Info” Choose “Downlink Frequency” or see the number next to UARFCN. This will give you a channel number, followed by some other numbers in brackets. The channel numbers correspond accordingly.
| Channel Number | Frequency |
| 4357-4458 | 850 MHz |
| 2937-3088 | 900 MHz |
| 10562-10838 | 2100 MHz |
How to Enable Field Test Mode in Android?
The process to access the field test mode in Android smartphones is different than iPhones. Open “Settings” and click on “General”. Now, choose “About phone” and select “Network”. A list of options will open. Signal strength will be displayed in dBm value. You can also dial ##4636## for a full engineering menu.
Dial *#0011# and look for the RSCP for the signal power and ECIO for the signal quality.
