How do you check mobile signal strength for IoT?
To check mobile signal strength for an IoT installation, read RSRP and SINR directly from the IoT router’s modem status page or via a professional tool like CellTester. Phone signal bars are not an accurate indicator — they reflect what a smartphone receives at standing height with an internal antenna, not what an industrial router with an external antenna will receive in its installed position.
Methods for checking mobile signal strength
| Method | Device tested | Gives RSRP/SINR | Multi-operator | Suitable for IoT commissioning |
|---|---|---|---|---|
| Phone signal bars | Your phone | No | No | No |
| iPhone Field Test Mode | Your phone | Yes (RSRP) | No | Indicative only |
| Android ##4636## | Your phone | Yes (RSRP) | No | Indicative only |
| Router admin page | The actual router | Yes | No (current SIM only) | Partial |
| CellMapper app | Your phone | Yes (from phone) | No (current network only) | Pre-survey only |
| CellTester | The actual router + antennas | Yes (all metrics) | Yes (automated sweep) | Full commissioning |
How to check signal on an iPhone (Field Test Mode)
- Open the Phone app and dial *3001#12345#* then press Call
- Field Test Mode opens. Select LTE from the menu
- Select Serving Cell Info
- Read rsrp0 (RSRP in dBm) and rs_snr (SINR)
- Note the freq_band_ind (LTE band) and pcid (Physical Cell ID)
Remember: this is your iPhone’s reading, not the reading of the router and antenna you are installing. It is useful for a rough site survey but should not be used as commissioning data.
How to check signal on Android
- Open the Phone app and dial *#*#4636#*#*
- Select Phone Information
- Scroll to find RSRP, RSRQ and SINR readings
On some Android devices this code does not work. Alternatively, go to Settings > About Phone > Status > SIM Status for basic signal strength.
Using CellMapper for pre-survey site planning
CellMapper (cellmapper.net) is a crowd-sourced database of cell tower locations across the UK. Before visiting a site, search by postcode to see which towers are nearby, on which bands, and which operators have coverage. This helps plan antenna direction and identify potential interference sources. Read the full CellMapper guide for the professional workflow.