What should I look for when buying an IoT antenna?
When buying an antenna for an IoT installation, the key specifications are: frequency band coverage matching your deployment technology (check LTE bands B20, B3, B28 for UK coverage), gain in dBi, number of ports (2 for 2x2 MIMO, 4 for 4x4 MIMO), cross-polarisation on MIMO antennas, connector type, and IP rating for outdoor use. Be sceptical of very high claimed gain figures on small form-factor antennas — physics limits what is achievable at a given frequency for a given physical aperture.
Specification checklist
| Specification | What to check | Minimum for UK IoT |
|---|---|---|
| Frequency bands | Covers B20 (800 MHz) and B3 (1800 MHz) at minimum | 698–2700 MHz broadband |
| Gain | Real gain at B20, not peak gain at B3 | 5 dBi at 800 MHz for directional |
| Ports | Match to router MIMO capability | 2-port for RUT200; 4-port for RUTX50 |
| Polarisation | Cross-pol (+45/-45 degrees) for MIMO gain | Cross-polarised dual or quad port |
| Port isolation | Higher is better for MIMO performance | 25 dB minimum between ports |
| IP rating | Outdoor installations require waterproofing | IP65 minimum for external mount |
| Connector | Match to router connector (SMA-M most common) | SMA-M or N-type with quality cable |
What to be sceptical of
- Very high gain claims on small antennas: A 3dBi gain omni and a claimed 9dBi omni the same physical size are not both telling the truth. Gain requires physical aperture.
- Single-band gain specs: An antenna claiming 10dBi at 1800 MHz may have 2dBi at 800 MHz. Check the gain figure at B20.
- Cheap pigtail cables included: Thin coax supplied with budget antennas can cost you several dB before the signal reaches the router. Replace with quality cable or short jumpers.