A directional antenna is an antenna that concentrates its radio energy in one direction, so it sends and receives strongly towards the mast it points at and weakly from everywhere else. The directional antennas used with cellular routers are usually panel, Yagi or log-periodic (LPDA) designs, fixed to a wall or pole and aimed at a chosen mast.

A directional antenna gets its extra gain by putting the same energy into a narrower beam, rather than spreading it all the way round like an omnidirectional antenna. Beamwidth is the angle across which the antenna delivers at least half its peak power, measured between the points 3 dB below the peak. The narrower the beamwidth, the higher the gain and the more precisely the antenna must be aimed. Directional antenna datasheets give both the gain in dBi and the horizontal and vertical beamwidth in degrees, and the two should be read together.

A directional antenna is the better choice where the signal is weak and comes from one distant mast, typically at rural sites, at the fringes of network coverage and in locations with heavy interference. By rejecting signals from other directions, a directional antenna improves the ratio of wanted signal to interference. On a router, that shows up as a stronger RSRP from the chosen mast and a higher SINR, which is what lifts data speeds.

A directional antenna ties the router to the masts in one direction, and that has costs. If the chosen cell is congested or out of service, the router has fewer alternatives than it would with an omni antenna. Wind, building work and changes to the mobile network can also mean the antenna needs re-aiming over time. On a multi-network SIM, the best mast for each network may sit in a different direction, so an antenna aimed at one network's mast can leave the others with weak signal and make failover between networks less dependable.

Aiming a directional antenna means pointing it towards the mast first, then fine-tuning in small steps while watching RSRP and SINR on the router's status page, pausing after each move so the readings settle. Most directional antennas for 4G and 5G are cross-polarised MIMO antennas: two elements set at right angles in one housing, each with its own cable to one of the router's antenna ports. We supply directional and omnidirectional cellular antennas and can help you decide which suits a site.