Answer first: the CG100 is the only Boost4U home repeater tuned to Band 20 plus Band 8: it lifts O2, Vodafone and Three 4G data through the 800 MHz layer, and keeps O2 and Vodafone ordinary 2G voice calls and SMS alive through the 900 MHz layer, with ≥45 dB uplink and ≥50 dB downlink gain, a ≥10 dBm licence-exempt output, a ≤5 dB noise figure, 100 m² of indoor space and 10 simultaneous sessions. It is built for the O2 and Vodafone household that loses both data and calls inside a stone or brick cottage; it does not repeat EE 2G voice (which sits on Band 3 at 1800 MHz), does not carry 3G Band 1, does not carry 5G, and stays rated for 100 m² rather than a whole house.

Band 20 (800 MHz): The Long-Range 4G Layer for O2, Vodafone and Three

Band 20 occupies the 800 MHz spectrum Ofcom freed up after the analogue TV switch-off. Its lower wavelength travels farther from the macro mast, bends around hills and hedgerows, and penetrates brick better than the higher-capacity bands, which is why O2, Vodafone and Three deployed it as the rural and deep-road 4G layer. On a village lane, Band 20 is the layer that keeps a data session alive between masts where higher bands fade.

Uplink and downlink frequency pairs for Band 20

A home repeater works on a paired FDD block: the phone transmits on one block and receives on another, and the amplifier repeats both directions without mixing them. The CG100 repeats the 832 to 862 MHz uplink and the 791 to 821 MHz downlink together so a phone that sends a request to the Band 20 tower hears the 4G reply amplified inside the living room.

Why 800 MHz reaches the far mast but carries less capacity

Lower frequency propagates farther and passes a stone wall or a hillside with less loss, but each MHz block carries fewer simultaneous data sessions than the higher bands. Band 20 is therefore the coverage band in the countryside: it keeps a phone connected at the edge of the mast range, while denser town capacity lives on other layers the CG100 does not tune. A Three user in Scotland, an O2 giffgaff home office in Cornwall, or a Vodafone Lebara household relies on Band 20 being repeated inside; the CG100 does that on the donor side before the ≥50 dB gain and ≥10 dBm output spread it across the room.

Band 8 (900 MHz): The O2 and Vodafone 2G Voice and SMS Layer

Band 8 sits at 900 MHz, the original GSM cellular band O2 and Vodafone maintain for circuit-switched 2G voice calls and SMS where VoLTE or 3G fallback is unavailable. Its wavelength penetrates internal stone and rendered walls more cheaply than 1800 or 2600 MHz, which is why an ordinary call often rings indoors even when the 4G bar count looks thin.

Uplink and downlink frequency pairs for Band 8

The CG100 repeats the 890 to 915 MHz uplink and the 935 to 960 MHz downlink so an O2 or Vodafone handset places and receives a normal circuit call inside the home even where the 4G data layer is weak. This is the feature that separates CG100 from a Band 20-only box: data alone does not keep a dropped call fixed, and Sarah M. in Yorkshire reported that calls no longer dropped once the CG100 carried the voice layer.

Why 900 MHz penetrates walls better than 800 MHz in practice

Band 8 at 900 MHz and Band 20 at 800 MHz sit close, but the 900 MHz GSM layer has decades of indoor building penetration behind it, travels through solid stone and rendered walls with modest loss, and remains the circuit layer older phones dial on. The 800 MHz Band 20 carries data capacity over distance; the 900 MHz Band 8 keeps the call legible inside the room; the dual-band chassis runs both at once rather than choosing one.

The Unique Band 20 + 8 Combo: 4G Data and Voice From One Box

Across the Boost4U home range, Band 20 repeats 4G data and Band 8 repeats 2G voice, and combining them in one chassis is the CG100's defining placement. A Band 20-only unit keeps data but drops the call when VoLTE is unavailable; a Band 8-only unit keeps the call but never accelerates the data session. The CG100 keeps both, which matches the O2 and Vodafone household that complains of both slow internet and dropped calls.

UK Network and MVNO Mapping: Which SIM Rides Which Band

The table below maps every SIM named on the CG100 product page to its host network and the band the booster repeats for it. Before ordering, check the SIM's host carrier rather than the shop brand, because the MVNO name itself does not appear on the tower.

An O2 giffgaff home-office phone sees both bands light up, a Vodafone Lebara handset keeps its circuit call on Band 8, and a Three data-only session rides Band 20 without a Band 8 call path. The mixed household benefits from different halves of the chassis, which is the practical reason a dual-band box beats a single-band purchase for families on two networks.

Gain and Output: ≥45/≥50dB Gain Plus ≥10dBm Home Output

Gain, measured in decibels, is the factor by which the amplifier lifts the weak donor signal before re-radiating it; output power, in decibel-milliwatts, is the transmit level the indoor whip radiates into the room. The CG100 carries both: ≥45 dB uplink and ≥50 dB downlink gain recover a faint rooftop donor, while ≥10 dBm spreads the recovered field across 100 m² for 10 sessions.

Why gain listens and output fills the room

Brick, stone and tinted glass hide the donor from a handheld phone; the ≥45/50 dB gain lifts that hidden signal back above the decode floor, and the ≥10 dBm output carries it to the sofa, kitchen and desk. This is a low-power licence-exempt home class, not a building repeater for a farmyard; the modest output keeps indoor radiation controlled while the gain does the recovery work.

Noise figure ≤5 dB at 10 sessions

A perfect amplifier adds no noise; every real amplifier adds some, measured as the noise figure. The CG100's ≤5 dB figure keeps added noise low enough that the amplified signal decodes cleanly rather than arriving louder but garbled, which matters when ten family members or colleagues share the home. A high noise figure raises the indoor floor, causes the phone to select a louder but noisier cell, and reduces usable uplink; a ≤5 dB figure is the standard repeater quality level.

Automatic gain control on a fixed donor

The automatic gain control balances recovered donor signal against the ≥10 dBm output as weather and daytime traffic change, backing off when a tower looms close and recovering when the donor fades behind a cloud or a roof. On a fixed wall-mounted home installation the AGC locks once and holds steadily, unlike a moving vehicle, which keeps re-locking between cells.

Dual-Band CG100 vs Single-Band C100 and the CD100 Band 20+3

The home range splits by tuned band, and choosing the wrong one leaves a whole service absent indoors.

C100: Band 20 alone for data, no voice path

The C100 reaches O2, Vodafone and Three 4G on Band 20 alone and suits a data-only household whose calls already ride VoLTE, but it leaves the Band 8 voice layer absent; an older O2 handset without VoLTE sees no boosted call even though data improves.

CD100: Band 20 + Band 3 for EE voice, not O2/Vodafone calls

The CD100 repeats Band 20 4G plus Band 3 at 1800 MHz for EE 2G voice, so it serves the EE family but leaves the O2/Vodafone Band 8 circuit call unboosted. The two units share a price but solve opposite voice problems.

CG100: the only Band 20+8 combo for O2/Vodafone calls

The CG100 keeps Band 20 and Band 8 in one chassis, so it is the only home unit in this comparison that serves O2 and Vodafone 4G data together with their ordinary 2G calls, which matters for a rural O2 or Vodafone household whose complaint is dropped calls rather than slow data alone.

VoLTE and the Band 8 Circuit Fallback

Modern phones place calls over the 4G data layer using Voice over LTE (VoLTE), while older handsets and areas without VoLTE fall back to circuit-switched 2G GSM. The CG100 supports both routes where the network offers them, but its support differs by band.

VoLTE on Band 20 for O2 and Vodafone

Where O2 or Vodafone has enabled VoLTE on Band 20, a modern handset places the call inside the boosted 800 MHz LTE session, and the CG100 repeats that session like any other data call. The booster does not negotiate VoLTE itself; the phone and network do, and the unit carries the already established 4G call across the room where the ≥10 dBm output reaches.

Band 8 2G fallback for non-VoLTE handsets

Where VoLTE is unavailable or the handset is older, the call returns to the Band 8 900 MHz circuit layer on 890–915 MHz uplink and 935–960 MHz downlink, which the CG100 repeats for O2 and Vodafone. A basic feature phone, an elderly relative's handset, or a phone in a VoLTE-not-yet-enabled area still rings and completes a normal call over the boosted 2G layer rather than dropping to no service indoors.

What the CG100 does not carry for calls

The unit does not tune 3G Band 1 at 2100 MHz, so a network that still routes voice fallback through 3G on your street receives no boost on that layer. Where VoLTE is off and the network relies on 3G circuit fallback rather than Band 8, a call may not complete inside the home even though 4G data shows bars; checking VoLTE support on the handset before ordering avoids that surprise, and neither gain nor output can invent a band the chassis does not tune.

Ofcom Licence-Exempt Status, UKCA, CE and RoHS Explained

Four marks sit on the CG100: Ofcom licence-exempt status, UKCA for the UK market, CE for European conformity, and RoHS for restricted hazardous substances. Each answers a different regulatory question, and none changes the tuned bands, the ≥45/50 dB gain or the ≥10 dBm output figure.

Ofcom licence-exempt and the home output class

Ofcom's permitted-class rules allow a low-power fixed repeater on licensed mobile bands without the owner holding a spectrum licence. The CG100 meets the output, isolation and installation conditions of that class, so no application, fee, annual renewal or registration number is required, provided the unit is used as supplied, the antenna separation of 10 m is respected, and it is not modified to raise output. The ≥10 dBm figure is the model's rated low-power output inside this class; the automatic gain control keeps the field balanced rather than running open-loop.

UKCA, CE and RoHS

UKCA confirms the product meets the applicable UK safety, electromagnetic compatibility and radio-equipment requirements for sale in Great Britain after the CE transition. CE confirms conformity with the European Union Radio Equipment Directive and related health and safety standards, which is why the same kit ships across the EU delivery list including Germany, France, Italy, Spain, the Netherlands, Belgium, Austria, Sweden, Denmark, Finland, Ireland, Portugal, Poland and the Czech Republic as well as the UK. RoHS restricts lead, mercury, cadmium and other hazardous substances in electronics, so the chassis, cable and adapter comply with waste-electrical rules rather than containing banned materials. None of these marks alters how the bands repeat; they confirm the unit may be sold and used without a separate permit.

Honest Limitations: No 3G Band 1, No 5G, 100 m² Only

A guide that lists only benefits misleads a buyer. The CG100 has three clear limits that should match your situation before you order, and neither the ≥45/50 dB gain nor the ≥10 dBm output removes any of them.

No 3G Band 1 at 2100 MHz

The CG100 tunes only Band 20 and Band 8. It does not repeat Band 1 at 2100 MHz, the 3G UMTS layer some networks still use for data fallback or circuit-switched voice. A street that relies on 3G where 4G fails sees that fallback unboosted indoors; raising gain cannot manufacture a band the hardware never receives, and this is the single most important technical limit for areas already served only by 3G rather than Band 20 or Band 8.

No 5G on any band

The CG100 does not tune n78 (3.5 GHz), n8 (900 MHz 5G) or any other 5G band, and it does not convert 4G into 5G. A 5G phone still receives its normal unboosted 5G signal from the macro tower, and the CG100 only lifts the 4G Band 20 data layer plus the Band 8 voice layer. Expect reliable 4G calls and data across the room, not boosted 5G speeds, no matter how high the gain.

EE 2G voice is not carried; 100 m² ceiling

EE runs its 2G voice on Band 3 at 1800 MHz, which the CG100 does not tune, so an EE household gets 4G data where reach applies but not a boosted EE circuit call; that gap belongs to the CD100. The rated space is 100 m² for a single room, small flat or home office supporting 10 sessions; it is not a whole-house system, and it will not blanket a farmyard or an extension beyond the far wall. A permanently sited space clearly beyond 100 m² needs a building-rated larger model rather than more vehicle or home output.

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