Antenna types and when to use them
| Type | Gain | Use case | Notes |
|---|---|---|---|
| LPDA (log-periodic) | 7-10 dBi | External mount, directional aim at tower | Best for maximising signal to a specific cell. Supports wide frequency range. |
| Panel / patch | 5-8 dBi | Wall or pole mount, moderate directionality | Good balance of gain and beamwidth. Common for CCTV and industrial. |
| Omni (whip/dome) | 2-5 dBi | Indoor or where direction is unknown | No aiming required but lower gain. Not suitable for weak signal locations. |
| MIMO panel (4 port) | 5-8 dBi per port | 4x4 MIMO routers (RUTX50) | Four separate antenna elements. Port isolation critical (25 dB minimum). |
MIMO and antenna selection
Modern IoT routers use 2x2 and 4x4 MIMO - multiple simultaneous data streams across separate antenna paths. For MIMO to deliver its theoretical throughput benefit, the antenna ports must be sufficiently isolated from each other and the antenna elements must present different signal paths (polarisation diversity or spatial diversity). An antenna advertising MIMO but with inadequate port isolation will deliver no MIMO gain and may actually reduce throughput compared to a single antenna.
Target port isolation: 25 dB minimum for 2x2 MIMO, 30 dB or better preferred for 4x4. CellTester measures RSRP on each port independently - if the delta between ports is above 10 dB, the MIMO link is degraded and the antenna installation should be investigated.
Cable loss and why it matters
Coaxial cable between the antenna and router introduces signal loss that reduces the effective gain of the antenna. The loss depends on cable type and length:
| Cable type | Loss at 800 MHz | Loss at 1800 MHz | Loss at 2600 MHz |
|---|---|---|---|
| RG58 (thin, cheap) | ~5 dB/10m | ~8 dB/10m | ~12 dB/10m |
| RG174 (very thin) | ~9 dB/10m | ~14 dB/10m | ~20 dB/10m |
| LMR-200 | ~2.5 dB/10m | ~4 dB/10m | ~5.5 dB/10m |
| LMR-400 | ~1 dB/10m | ~1.6 dB/10m | ~2.3 dB/10m |
A 7 dBi LPDA antenna with 10 metres of RG58 cable at 1800 MHz delivers net gain of -1 dBi. The antenna is actually making things worse. Use LMR-200 or better for cable runs over 3 metres.