Testing mobile signal strength from your phone is useful for pre-site surveys and quick coverage checks. This guide covers every method on iOS and Android, what readings mean, and where phone-based testing ends and professional router-based commissioning with CellTester must begin.
iPhone - Field Test Mode in detail
Dial *3001#12345#* → Call. iOS 16+: Field Test app opens directly with full menu. iOS 15 and earlier: press Home after dialling to display numeric dBm in the status bar.
Key readings to find on iOS 16+:
- LTE → Serving Cell Meas → RSRP, RSRQ, SINR, RSSI
- 5G NR → NR Serving Cell Info → SS-RSRP, SS-RSRQ, SS-SINR
- LTE → Neighbour Cell Info → signals from adjacent cells (useful for interference diagnosis)
- LTE → Timing Advance → distance estimate to serving tower
- Physical Cell ID → PCI for CellMapper cross-referencing
Switching operators on iPhone for comparison: Settings → Mobile Data → Network Selection → Manual. Select each operator, return to Field Test Mode, note RSRP. This is slow (30-60 seconds per operator) compared to CellTester's automated sweep, but useful for a quick pre-site check.
Android - engineering modes
Samsung (*#0011#): Opens Service Mode showing RSRP, RSRQ, RSSNR, band and EARFCN in real time. Most useful quick-access Android engineering tool.
Settings (all Android): About Phone → Status → SIM Status → Signal Strength. Updates slowly - allow 30 seconds for stabilisation at each location.
Network Cell Info (app, Android): Shows RSRP, RSRQ, RSSNR, CQI, band, EARFCN and cell location on a map. Includes logging for walking surveys. Best free option for pre-site work.
The consumer vs professional testing distinction
Phone-based signal testing - whether iPhone Field Test Mode or Android engineering mode - measures what the phone receives with its internal antenna. This is categorically different from what the Teltonika router being installed will receive with its external antenna in its final mounting position. Differences of 10-20 dB are common. Use phone testing for planning. Use CellTester for commissioning.