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What is CEL-FI?

The award-winning line of CEL-FI mobile signal boosters is manufactured by Nextivity. CEL-FI products improve signal between a mobile phone and a mobile network tower, allowing you to have clear voice conversations and a stable data connection inside buildings. At its most basic, each CEL-FI system consists of a donor antenna, a mobile signal booster and a server antenna.

The donor antenna is placed in the area where the strongest native signal can be received from the carrier network, usually outside or close to a window; signal levels as low as -120 dBm are acceptable. The donor antenna transmits the native mobile signal to the CEL-FI mobile signal booster unit which amplifies the signal. The enhanced signal is passed to the server antenna where it is broadcasted within the interior of the building, enabling better quality calls and greater data throughout.

Is CEL-FI Legal?

Yes, every product in the CEL-FI range is compliant with Ofcom’s new licence-exempt requirements (IR2102) and legal to use in the UK. CEL-FI solutions are also licence-exempt under ComReg S.I.No.283 of 2018 requirements for Ireland.

Mobile operators have historically adopted an extremely strict policy against the use of user-installed mobile phone signal repeaters and boosters on their networks, as they caused interference and damage to the performance of the networks. It is for this reason that Ofcom consider many mobile signal repeaters illegal. Due to its unique intelligent features, CEL-FI is classed as a smart repeater and is one of the few user-installable legal mobile phone repeater permitted in the UK.

For more infomration please see our Ofcom compliance page.

What is a mobile signal repeater and is it legal to use one?

A mobile signal repeater is a radio device that works to boost mobile network coverage for users. They amplify frequencies from mobile network providers via reception antennas. All radio devices must meet regulations set out by Ofcom (IR2102) (UK) and ComReg S.I.No.283 of 2018 (Ireland).

Most mobile phone signal repeaters are known for interfering with mobile network providers and as a result Ofcom does not licence any signal repeater in the UK, making them an illegal technology.

CEL-FI’s technology is more advanced, allowing mobile network providers the ability to monitor and regulate the use of CEL-FI units themselves. For this reason they are classified as Smart Repeaters and are some of the few mobile phone repeaters which can legally be used in the UK and Ireland.

Does CEL-FI require an internet or GPS connection?

No. The CEL-FI system only needs 1 bar of native mobile signal, in one spot of in your building to be able to cover your entire home, office, commercial or industrial space, or public building.

What is the difference between a mobile signal repeater and a Wi-Fi signal repeater?

Wi-Fi (wireless fidelity) is a wireless networking technology used to connect your laptop, mobile phone, tablet or other internet-enabled device to your broadband/internet provider. Wi-Fi signal repeaters (or boosters) are devices that increase the reach of your Wi-Fi network to improve connectivity in areas where the signal is weak. A booster amplifies a weak signal to eliminate Wi-Fi blackspots and give fast connectivity all over the home.

Mobile signal connects your phone or device to a mobile network carrier. Mobile signal repeaters (or boosters) improve the mobile signal received from mobile networks in indoor areas. They focus specifically on improving voice clarity and reduce dropped calls for mobiles in areas with poor network coverage, as well as increasing download speeds and improving streaming and internet browsing on mobile broadband enabled devices.

CEL-FI can turn one bar of mobile signal into up to 5 bars and can retransmit the amplified 3G / 4G / 5G signal to other areas that have little or no coverage. Unlike Wi-Fi boosters, CEL-FI does not require a broadband connection.

What technologies does CEL-FI support?

All signal boosters are carrier approved to support 3G / 4G / 5G for voice and data.

Will certain materials in my building affect the unit from working correctly?

Certain building materials can affect the coverage area of CEL-FI units. Older buildings tend to use more materials and have thicker walls, therefore reducing the radius coverage. Modern construction materials such as foil-backed insulation and thermally-reflective glass can have a similar effect. If you would like to discuss a particular material in further detail with one of our advisors, please contact us.

How do I know if my CEL-FI system is compatible with an external antenna?

Every product in the current CEL-FI range can be connected to an external antenna. An external antenna is required when there is inadequate signal strength available within the property.

If you have an older system which is failing to detect a signal in a new property or on a new network etc. you can check the model number on the label, which will have an '_EXA' suffix (e.g. D32-1/3_EXA) if an external antenna can be used. Another way to determine external antenna compatibility is by looking at the Network (window) Unit; if there is a gold threaded fitting on the back then an external antenna can be attached.

What's the radiation level of CEL-FI units?

CEL-FI signal boosters are safe. We test the CEL-FI units like a phone for a Specific Absorption Rate (SAR) rating. Anything with a SAR rating of less than 2.0 is defined as 'touch safe'. Both the CEL-FI window unit and coverage unit have a SAR rating below 2.0.

Technically measuring SAR is usually only done for hand-held or body worn devices so Wi-Fi routers generally do not have SAR ratings. The power emitted from CEL-FI devices is no greater in general than any other consumer wireless networking devices and smart phones.


What networks are compatible with CEL-FI?

CEL-FI signal boosters are compatible with all four of the UK mobile operators: EE, O2, Three or Vodafone. However, within these networks there are also Mobile Virtual Network Operators (MVNOs). Please check our Networks page for list of the most common MVNOs and the operator they use.

Please note that MVNOs may occasionally change their host network. If this happens, please contact us about reconfiguring your CEL-FI unit. Please also note that network operators have the right to shut down your system at any time, without notice.

Does it work with other networks that are not listed above?

Signalboosters only sell CEL-FI signal boosters configured to UK based networks which comply with the Ofcom (IR2102) (UK) and ComReg S.I.No.283 of 2018 (Ireland) regulatory requirements.

However, CEL-FI is authorised by almost 200 mobile operators worldwide and can be reconfigured to other networks using the Wave app. Signalboosters claim no responsibility for product performance in other countries which may have different regulatory requirements.

Does CEL-FI work for multiple networks?

Yes. Following an update to regulations brought in by Ofcom in June 2022, multi-operator repeaters are now permitted in the UK.

We have a selection of products able to boost multiple networks simultaneously.

Whilst the rest of the CEL-FI range can only boost a single network at one time, it is possible to change the operator using the CEL-FI Wave™ mobile app, should your provider change in the future.

Does a CEL-FI system have to be activated or provisioned on in the mobile operator's network?

Yes. In the UK all CEL-FI units must be registered using the Wave mobile app available for Apple/iOS and Android mobile devices. Other networks may or may not require registration.

Is CEL-FI operator or service provider specific?

Yes. Each CEL-FI system is configured to work on an individual operator network or selection of operaor networks.

Can you reconfigure the unit’s network if you change mobile networks?

Yes. If they were supplied by CEL-FI units can be re-configured to other networks using the Wave mobile app if you change your mobile network. Units sullied directly through the UK mobile networks cannot be reconfigured to other networks.

Does CEL-FI require maintenance or adjustments if changes occur to the serving mobile network?

No, CEL-FI does not require maintenance, and it will automatically adjust to changing mobile network situations.

Will CEL-FI work with my Apple device?

Yes. All iPad and iPhone versions are supported by CEL-FI systems sold on this web site.

Does Cel-Fi work internationally?

CEL-FI units are set to particular frequencies and locked to the network identity (referred to as the 'PLMN-ID'). Therefore CEL-FI devices typically only work for the particular country and network they are sold to. Only the manufacturer, Nextivity, can create the configuration for any given network.

I am living outside the UK and want to purchase from this site. Will the CEL-FI unit work in a different country?

CEL-FI offer various configurations for a range of EU networks. Please contact us to find out if we can support you.


How do I install my CEL-FI signal booster?

Please view our Resources page for installation videos, quick start guides and data sheets for CEL-FI products.


What is IntelliBoost®?

CEL-FI's IntelliBoost® is the first processor designed specifically to optimise the indoor transmission and reception of 3G / 4G / 5G wireless signals in silicon. With advanced filtering, equalisation, and echo cancellation techniques, Nextivity has developed an embedded architecture which delivers unprecedented in-building data rates and pervasive 3G / 4G / 5G connectivity. The IntelliBoost® processor ensures that CEL-FI products never negatively impact the mobile network while providing maximum coverage.

Is CEL-FI a mobile phone signal repeater?

Mobile phone signal repeaters are classified as radio devices. They work to boost mobile phone signal; however, some boosters / repeaters can interfere with mobile operator networks and therefore are considered illegal as laid out by Ofcom.

CEL-FI is different in that it is considered a smart repeater under the criteria set by Ofcom. A Smart Repeater is a mobile phone signal booster that is connected to a single mobile network and allows the host mobile network to control the device. Unlike mobile phone signal repeaters, smart repeaters do not interfere with the mobile network’s coverage and are therefore considered a legal mobile signal booster.

Why is 100dB of gain so important?

System gain is critical to a booster’s performance because it tells us how much a signal may be improved and how beneficial the boosted signal can be. Example: If you have a low-level signal such as -90 dBm per carrier, adding 100 dB of System Gain gives +10 dBm per carrier which can cover a large area. In contrast adding only 70 dB of gain would only give -20 dBm of signal per carrier which would only cover a very small space. Therefore, a booster with a gain of 70 dB would need a very strong donor signal to be of much use, regardless of the stated transmit power that likely is going unused. In other words, the higher the gain of the booster, the better it will work, even when far away from a base station.

Most traditional analogue boosters only provide up to 60dB to 70dB of gain. CEL-FI can provide up to 100dB of gain; 1,000x more than powerful than traditional boosters.

Does CEL-FI cause significant degradation to mobile network quality as traditional repeater products often do?

No, CEL-FI products are unconditionally network safe.

CEL-FI utilises an intelligent processor to actively adjust to the network environment. It uses multiple techniques including automatic gain control, real-time path loss analysis, and uplink signal gating to ensure that it never degrades the quality of the macro network signal or artificially raises the noise floor of the node B.

What makes CEL-FI different from other smart signal boosters?

CEL-FI relies on intelligent, self-organising algorithms to maximise the area of coverage for users while ensuring that it does not compromise or interfere with mobile operator networks or impede other subscribers' signals. CEL-FI does not require any new equipment or changes to existing network infrastructure, or mobile devices. Recognised for its superior design and effectiveness, CEL-FI is one of the few consumer mobile signal boosters authorised by the communications commissions (Ofcom IR2102) in the United Kingdom and ComReg S.I.No.283 of 2018 in Ireland.


I need some technical help with an error I am getting on my CEL-FI unit.

Try running the “CEL-FI Wave” mobile app on your Apple or Android mobile device and connect to the CEL-FI Coverage Unit using Bluetooth. The mobile app will prompt you, if required, to enter registration information and offer trouble-shooting tips.

If the issue is still not resolved after carrying out the instructions on the troubleshooting guide, please contact a member of our customer service team.


How do I stop an order I've made?

We process orders very quickly via an automated process, so please contact us as soon as possible! We will do our best to stop the order or make the needed changes but please be aware that any orders already processed cannot be stopped. In this case, you would be required to follow the returns policy.

My order shipped and I want to cancel.

In the event we are unable to stop the order, we can of course offer you a return service. To request this, please fill out a returns form and email it to our support team, who will issue a Return Merchandise Authorization number (RMA#). After receiving the RMA#, please add this to the returns form and send it back with the unwanted order. Please note: Signalboosters will not cover return postage costs for unwanted products. For further information visit our Returns section.

I ordered by mistake.

In the case of an incorrect order, we will gladly help you place the correct order and provide you with all the details you need to return the item that was ordered incorrectly. Please contact our customer service team as soon as you are aware of the mistake to avoid unnecessary shipping costs.