Short answerA 4G antenna does not create or boost signal. It picks up signal at a better place, such as outside a cabinet or higher on a building, and carries it down a cable to the router. Use two antennas (or one dual MIMO antenna) for 4G, keep the cable short, and choose directional only when you know where the mast is.
“Signal booster” is consumer language, and it leads people to buy the wrong thing. For routers, think of an antenna as moving the router’s ears to somewhere they can hear better.
Why the antenna position matters most
Walls, metal cabinets, foil-backed insulation and the ground all absorb signal. An antenna mounted outside, above the roofline or simply on the right side of a building can see a much stronger and cleaner signal than the router can from inside. That improvement usually dwarfs any difference in antenna gain.
Omni or directional?
| Omnidirectional | Directional | |
|---|---|---|
| Pattern | Hears all around | Focuses one way |
| Best for | Vehicles, unknown mast location, decent signal | Fixed rural sites, weak or noisy signal |
| Setup | Mount and go | Must be aimed at the right mast |
| Effect on SINR | Neutral | Can improve it by ignoring other cells |
Gain, in dBi, describes how much an antenna focuses its pattern, not how much power it adds. A high-gain omni has a flatter pattern, which can be worse on a hillside where the mast is above or below you.
Router Store has omnidirectional, directional and vehicle 4G antennas.
MIMO: why there are two connectors
4G routers use MIMO (multiple input, multiple output), sending and receiving over two antennas at once. Both main antenna ports should be connected. Using only one roughly halves the potential download speed and weakens the connection. A MIMO antenna has two cables in one housing. For directional MIMO, the two elements are cross-polarised, so do not swap them for two random antennas.
Cable: shorter is better
Every metre of coaxial cable loses some signal, and thin cable loses much more than thick, low-loss cable, especially at higher frequencies. A great antenna on 15 metres of thin cable can be worse than the router’s own stubby antennas. Keep runs short, use low-loss cable for longer distances, and avoid unnecessary adaptors. See Router Store’s antenna cables.
Connectors
Most business routers use SMA connectors; some smaller devices use TS9 or similar. Check both ends before ordering. A wrong adaptor adds loss and another failure point.
Frequently asked questions
Will an antenna make my 4G faster?
If the router’s current position is the problem, yes, often dramatically. If the mast is overloaded, no antenna will fix that.
Do I need a 5G antenna for a 4G router?
No, but a 5G antenna that covers the 4G bands works fine and keeps you ready for a 5G upgrade.
How high should I mount it?
High enough to clear nearby obstructions in the direction of the mast. Even a couple of metres can help a lot.
NANick Appleby
Nick Appleby has worked in UK telecoms since 1998, starting at BT, and has spent most of that time on cellular routers, data SIMs and the antennas that connect them for business and industrial sites. He writes 4G SIM to explain how the networks and the kit actually behave, in plain English.