Three signal boosters for business premises
Calls that don’t drop and data that works, in every corner of your building. We survey, design, install and support operator-approved CEL-FI systems for Three across the UK.
- Ofcom-compliant and legal
- Single-network or all four networks
- 4G and 5G
- Installed and supported UK-wide
Your free signal assessment
An engineer measures your building and tells you exactly what will fix it.
- Three signal, room by roomWhere it drops, and by how much.
- The best donor signalWhere the outdoor antenna should go.
- A design and a fixed quoteNo obligation, no surprises.
Why Three signal drops indoors
Three’s signal is strong outdoors in most towns, but much of it uses higher frequencies that struggle to pass through walls, so indoor coverage can be patchy.
Higher frequencies
Higher bands carry lots of data but lose strength through walls.
Coated glass
Modern windows block signal that would otherwise reach desks.
Lower floors
Basements and car parks often have no Three signal.
Rural sites
Away from towns, the nearest Three mast may be far off.
Outdoor Three signal, brought inside
- CaptureA donor antenna on the roof picks up the strongest Three signal we measured during the survey.
- Clean and amplifyA Nextivity CEL-FI unit boosts that signal without interfering with the network or your neighbours.
- SpreadSmall indoor antennas cover every floor, so phones get full signal wherever people work.
From survey to full signal, usually in weeks
One team does the whole job, so there is one point of contact from the first call to ongoing support.
- 1SurveyWe measure Three signal inside and out.
- 2Design and quoteAntenna plan and a fixed price.
- 3InstallOur own engineers, with minimal disruption.
- 4Test and hand overWe prove the coverage before we leave.
- 5MonitorOptional 24/7 signal monitoring. Learn more
Only legal boosters
Many boosters sold online are illegal in the UK and can disrupt the network for everyone nearby. We install only Ofcom-compliant, operator-approved systems.
Three signal before and after our installations
We survey every building before and after installation with our own survey app. These are real Three readings from recent projects.
Average signal strength (RSRP) across each surveyed floor. Usable means better than −107 dBm, the level phones need for reliable calls over 4G.
Recent Three projects
Three signal boosters: common questions
Are boosters for Three legal in the UK?
Yes, if they meet Ofcom’s rules. Since the Wireless Telegraphy (Mobile Repeater) (Exemption) Regulations 2018, approved single-network boosters can be used without a licence. Multi-network systems need the networks’ consent, which we arrange. Unapproved boosters bought online are illegal, and Ofcom can act against anyone using one.
Does it boost 5G as well as 4G?
Yes, with the right system. The survey shows which Three 4G and 5G bands reach your building, and we recommend CEL-FI equipment that carries them.
How long does installation take?
It depends on the size of the building. The quote includes an installation plan, and we work around your opening hours to keep disruption low.
Can one system cover every network?
Yes. A multi-network CEL-FI QUATRA system covers EE, O2, Vodafone and Three, so staff and visitors get signal whichever network they use.
Will a booster work if there is no signal outside?
A booster needs some outdoor signal to work with. The survey finds the strongest signal around your building. If there is none, we will tell you and suggest the alternatives.
Other networks
Three boosters for your building
Ready for full Three signal?
Book a free signal assessment and get a design and fixed quote.