Choosing and aiming an outdoor 4G/5G antenna

An outdoor antenna connected to a 4G/5G router is the most effective fix when the signal inside a building is too weak. It works by doing two things a router indoors can't: it sits outside the walls, and it concentrates its sensitivity in the direction of the mast.

Is it worth it?

Check your router's readings first (our router placement guide explains how). An outdoor antenna is usually worth it when, at the best indoor spot:

• RSRP stays below about -105 dBm, or
• SINR stays below about 5 dB, or
• the connection drops regularly.

If the signal is already good indoors and speeds are still slow at peak times, the cell is busy and an antenna will not help much.

Which type of antenna

Three more points matter as much as the type:

• Frequency range. For 5G on 3.5 GHz, the antenna must be rated up to at least 3.8 GHz. Many older "4G" antennas stop at 2.7 GHz.
• MIMO. Modern 4G and 5G use two or more antenna paths at once. A "2x2 MIMO" antenna has two connectors and needs two cables to the router. Using only one roughly halves the potential speed.
• Connectors. Routers usually have SMA or TS-9 sockets; outdoor antennas often use N-type. Plan the right cable or adapters.

Aiming at the right mast

1. Search your address on the map and find the masts of your router's carrier. Note the compass direction of the nearest one and of one or two alternatives.
2. If you want an exact bearing, enter your position and the mast's position in our bearing and distance calculator.
3. Point the antenna in that direction with a compass or a phone compass app. In France the difference between magnetic north and true north is small, a degree or two, which doesn't matter for a panel antenna.
4. Fine-tune: turn the antenna a few degrees at a time, waiting about a minute at each position, and keep the position with the best SINR rather than the best RSRP.

Try the alternative masts too. A mast slightly further away with a clear view can give a cleaner signal than the nearest one.

Cable: where the gain gets lost

Coaxial cable loses signal with length, and the loss grows with frequency. Thin cable such as RG-58 can lose around half the signal over just a few metres at 2.6 GHz, more at 3.5 GHz, which can cancel the antenna's gain completely.

• Keep the cable as short as possible: mount the router close to the antenna if you can (for example in the attic) and run network cable to the rest of the home instead.
• Use low-loss cable of the LMR-400 type or equivalent for runs longer than a few metres.
• Avoid unnecessary adapters and joints; each one adds a little loss.

Mounting

• Higher is usually better: a mast on the gable end or chimney often beats a wall bracket.
• Keep the antenna clear of metal objects and other antennas.
• Seal outdoor connectors against water with self-amalgamating tape.
• On a building with several owners (copropriété), check the rules before fixing anything to the facade or roof.

Not to be confused with a TV aerial

Many searches for "antenna installer" are about TV reception. A TV aerial receives digital terrestrial TV from broadcast transmitters, which are different sites from mobile masts. Many TV aerial installers can also fit 4G/5G antennas, but make sure they know which mast and carrier to aim at.

A word on signal boosters

Active repeaters that amplify mobile signals are strictly regulated in France and many sold online are not legal to use. They can interfere with the network for everyone nearby. Ask your carrier before buying one. A passive outdoor antenna connected to a router does not have this problem.