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Best mobile signal booster 2020: Fix your flaky 3G or 4G signal with the top, fully legal boosters

Expert Reviews Staff
22 Oct 2020
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Struggling with a signal blackspot? Find out if a mobile signal booster can help

A flaky mobile signal can be infuriating and the network operators are rarely much help. But you can banish the problem once and for all by buying your own mobile signal booster.

The hardware isn’t hard to find. You can buy boosters from numerous online stores and installation doesn’t have to be difficult, either. However, it’s important to pick the right sort of booster, as there are several different types. And while certain boosters are licence-exempt, meaning anyone can own and operate them in the UK, there are legal restrictions that you need to be aware of. If you’re not careful, you could be exposing yourself to a telling off, a nasty fine or even worse.

Here’s our expert guide to mobile signal boosters, plus our pick of the best mobile signal boosters on the market.

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How to choose the best mobile signal booster for you

What does a mobile signal booster do?

A booster is designed to improve your mobile coverage in areas where the signal is weak, such as inside a house or office building. If you can barely make a call without the sound breaking up, or if your data connection keeps timing out, a mobile signal booster could help.

There are four basic types of booster available in the UK for individual use:

A static indoor repeater is designed to improve coverage inside a building. It normally consists of three parts: a large “downlink” antenna that's located outdoors, a smaller “uplink” antenna inside the building and an amplifier that relays the signal from one to the other. The idea is that your mobile phones and other cellular devices can connect to the indoor antenna and get coverage that’s at least as good as if they were located outside.

A low-gain mobile repeater works on a similar principle, but is designed to improve the signal inside a moving vehicle. It consists of an external antenna connected to a cradle inside the vehicle, so again you get roughly the same signal strength inside your car as you would outside. Of course, if external coverage is patchy, this may not help: don’t rely on one of these to keep you connected if you’re, say, driving through the Scottish Highlands.

A different type of booster is the femtocell – basically a compact mobile base station that connects to a fixed broadband connection. If your home or office suffers from low-quality voice calls, a femtocell can make a huge difference by routing the traffic over your wired internet line, rather than through the air. Typically, femtocells can connect up to eight smartphones at once.

Finally, a smart repeater is a standalone indoor repeater that directly boosts the main mobile signal, giving nearby devices a better connection. It’s not legal for you to buy and operate a smart repeater of your own, but your mobile network can provide you with an approved and licensed one, giving you the best possible coverage indoors.

Where can you get a mobile signal booster from?

Networks sometimes provide repeaters to business customers as part of a service contract to ensure that the business gets an acceptable level of coverage. Femtocells may also be provided to smaller businesses and individuals in locations where the signal isn’t good enough for reliable voice calls. If you’re struggling to get a usable signal, it’s worth contacting your network and seeing if they can provide a booster before you splash out on your own.

If you decide to buy a mobile signal booster, you’ll probably need to look online. Of the major mobile networks, only O2 now sells a booster – the O2 Boostbox – and even then, only to its business customers. The other networks have now moved away from signal boosters, and instead steer their customers towards Wi-Fi calling features (see below).

Otherwise, the market for mobile signal boosters can be a bit of a Wild West affair, with quite a few disreputable operations selling through eBay or their own online stores. There are some solid and legitimate options, though. If you’re buying, check that any boosters sold are Ofcom-compliant – the reseller will usually advertise this heavily on their store – and check what return policy they offer if the booster fails to work at your home or business.

Are mobile signal boosters legal?

It’s legal to buy and sell any sort of mobile signal booster, but Ofcom maintains strict regulations governing their use. If you’re caught operating a booster that isn’t licence-exempt, your equipment could be confiscated, and for serious or subsequent infringements you could be looking at a fine of up to £5,000 or even a year in prison.

If that sounds harsh, it’s because repeaters (and, to a lesser extent, femtocells) can interfere with the public signal, amplifying noise and reducing capacity for other users. It’s a potential public nuisance, and the nearer the booster is to the base station, the worse this gets.

To qualify as licence-exempt, a repeater must only boost the signal of one network at a time. You can buy wideband repeaters that cover multiple networks, but these are illegal to use in the UK without a licence, as that they can impact every network in the area at once.

With a static indoor repeater, the uplink antenna also has to be located inside a building, rather than outside, to minimise interference. Similarly, a low-gain mobile repeater must only assist coverage inside a road vehicle, not inside a static caravan or boat.

Finally, there are some technical regulations covering amplification levels and transmission power. A licence-exempt repeater must automatically adjust the signal amplification according to how close the base station is, so a repeater near the base won’t amplify as much as one near the edge of the cell. Otherwise, a high-powered amplifier located near the base station could cause major interference affecting a large number of customers.

Do mobile signal boosters really work?

If your signal is poor, a booster can certainly help. I live in a coastal area, in a house that seems purpose-built to keep you on two bars or less; in some rooms I can barely make or take a call. Plugging in Nextivity’s Cel-Fi Go X booster instantly raised my signal strength from just under -120dBm to over -80dBm. According to inPocket’s Phone Signal Strength app, that’s a raise from “low” quality to “good” – and the effect on my 4G data speeds was unmissable, with download rates leaping from 9.45Mb/sec to 30.2Mb/sec while uploads rose from 0.11Mb/sec to 6.19Mb/sec. Not a bad result!

Bear in mind, though, that a booster might not be your only option. If you have ADSL or fibre broadband, your network might support Wi-Fi calling, whereby your phone connects to the network through your broadband connection whenever you’re in range of your router. You could also make use of Skype, FaceTime, Google Hangouts and other VoIP services while you’re in the building.

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The best mobile signal boosters you can buy in 2020

1. Cel-Fi Prime: Best for homes and small businesses

Price: £580 | Buy now from Signal Boosters

It’s not exactly cheap, but the Cel-FI Prime is probably the easiest and most affordable option for homes and small businesses,  giving you 80dB of gain within an area of roughly 110m². It consists of two parts: a Cel-Fi coverage unit and the Prime signal booster, which looks a little like a child’s cricket bat without the handle. The coverage unit plugs in to a power socket in a weak signal area, while the booster mounts vertically on a wall where you get the best signal – something Cel-Fi’s setup app can help you find. Versions for the EE and Three networks are available, and the Prime is compliant with Ofcom’s regulations. It’s easy to use and effective, although those with a larger property to cover might want to look at the Cel-Fi Go X, below.

Key specs – Licence-exempt: Yes; Signal gain: 80dB; Claimed coverage: 110m²; 3G/4G boost: Both; Major networks supported: EE, Three

Buy now from Signal Boosters


2. Cel-Fi Go X: Best for larger homes and offices

Price: £750 or £910 with antennae | Buy now from Signal Boosters

The Cel-Fi Go X repeater is bigger and more expensive than the Prime, and it’s more complicated to install: the large downlink antenna is designed to be mounted on a pole or the exterior of the building, where it connects to the chunky amplifier unit on the inside, which in turn connects to a hat-shaped omnidirectional antenna to support all the phones. The advantage is that the outdoor antenna should ensure you get the strongest possible connection, and the system claims a huge 1,400m² coverage for the amplified signal, so it’s ideal for larger offices and industrial units.

Once in place, the Go X is a very solid bit of kit – even the power supply cable screws firmly into place. Again, you can configure it and monitor performance from the Wave app, and (unlike the Prime) it supports all four major UK networks, plus virtual network operators.

Key specs – Licence-exempt: Yes; Signal gain: 100dB; Claimed coverage: 1,300m²; 3G/4G boost: Both; Major networks supported: O2, EE, Three, Vodafone

Buy now from Signal Boosters

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