CW100 Band 20 + 1 Explained: How the Dual-Band Booster Delivers 4G LTE Data and 3G All-Networks in 100m² UK Homes and Offices
The Boost4U CW100 repeater repeats two UK layers in a single room, small flat, cottage, home office or shop: Band 20 at 800 MHz carries EE, O2, Vodafone and Three 4G LTE data on 832–862 MHz uplink and 791–821 MHz downlink, while Band 1 at 2100 MHz carries EE, O2, Vodafone and Three 3G UMTS data plus voice on 1930–1990 MHz uplink and 2110–2180 MHz downlink, using ≥45 dB uplink and ≥50 dB downlink gain with a ≥10 dBm output, a ≤5 dB noise figure, a 5 dBi omni and a 3 dBi whip to cover up to 100 m² for 10 simultaneous users. This deep-dive explains why 800 MHz fits rural 4G coverage, why 2100 MHz keeps an all-network 3G fallback and call alive, how 45/50 dB gain and the 10 dBm output amplify both, which UK networks and MVNOs ride which band, how the CW100 compares with the Band 20+8 CG100 and the Band 20+3 CD100, how 3G fallback and VoLTE travel, what Ofcom licence-exempt status and the UKCA, CE and RoHS marks mean, and the honest limits: no 2G voice on Band 8 or Band 3, no 5G, and 100 m² only.
Answer first: the CW100 is the Band 20+1 repeater for 100 m²: it lifts EE, O2, Vodafone and Three 4G data through the 800 MHz layer and keeps the same four networks' 3G data and voice alive through the 2100 MHz layer, with ≥45/50 dB gain, a ≥10 dBm output, a ≤5 dB noise figure, 10 handsets and the omni outside. It suits the household or small office that loses 4G indoors and still wants a working 3G fallback on every network; it does not carry 2G voice on Band 8 or Band 3, does not do 5G, and stays rated for one room or a small flat rather than a whole large house.
Band 20 (800 MHz): The Rural 4G LTE Coverage Layer
Band 20 occupies the 800 MHz spectrum Ofcom freed after the analogue TV switch-off. Its longer wavelength travels farther from the rural mast, bends around hills and hedgerows, and penetrates brick better than higher bands, which is why EE, O2, Vodafone and Three use it as the country-road and deep-building 4G layer. On a Devon cottage, Norfolk farm edge or Cornish lane, Band 20 is the layer that keeps a data session alive between masts.
Paired transmit and receive frequency blocks for Band 20
| Band 20 link | Direction | Frequency range | Users on this layer |
|---|---|---|---|
| Uplink | Phone to tower | 832 to 862 MHz | EE, O2, Vodafone, Three and MVNOs 4G |
| Downlink | Tower to phone | 791 to 821 MHz | EE, O2, Vodafone, Three and MVNOs 4G |
The CW100 works on a paired FDD block: the handset transmits on one block and receives on another, and the amplifier repeats both directions without crossing them. The unit 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 across the room, with the omni catching the donor above the roof.
Why 800MHz reaches the far mast but carries less capacity
Lower frequency propagates farther and passes a stone wall, hillside or hedgerow with less loss, but each block carries fewer simultaneous sessions than the higher-capacity bands. Band 20 is therefore the coverage band in the countryside and on the industrial fringe: it keeps a connection at the edge of a mast's range, while denser town capacity lives on other layers the CW100 does not tune. An EE cottage in Devon, an O2 giffgaff home in Yorkshire, or a Three user in Scotland relies on Band 20 being repeated inside; the chassis does that on the donor side before the 50 dB downlink gain and 10 dBm output spread it across the room.
Band 1 (2100 MHz): The All-Network 3G UMTS Data and Voice Layer
Band 1 sits at 2100 MHz, the 3G UMTS band EE, O2, Vodafone and Three still maintain for data fallback and circuit voice where 4G is thin or absent. Its shorter wavelength carries more local capacity but does not bend around hills as far as 800 MHz, which is why it serves the near-mast 3G layer rather than the far-rural coverage band.
Paired transmit and receive frequency blocks for Band 1
| Band 1 link | Direction | Frequency range | Users on this layer |
|---|---|---|---|
| Uplink | Phone to tower | 1930 to 1990 MHz | EE, O2, Vodafone, Three and MVNOs 3G |
| Downlink | Tower to phone | 2110 to 2180 MHz | EE, O2, Vodafone, Three and MVNOs 3G data and voice |
The CW100 repeats the 1930 to 1990 MHz uplink and the 2110 to 2180 MHz downlink so a handset places a 3G call and falls back to a 3G data session inside the room even where the Band 20 4G layer is weak. This is the feature that separates CW100 from the 4G-only models: when 4G fades, the Band 1 layer keeps the call and a slow data link alive rather than dropping to no service.
Why 2100MHz matters as a fallback rather than a long-range band
Band 1 does not replace Band 20 for distance; it covers the nearer mast with 3G voice and fallback capacity when 800 MHz 4G cannot decode inside. In a home office where a video call would freeze on a thin 4G bar, the repeated 3G layer keeps the call legible; in a valley where 4G never arrives, the near-mast 3G still rings. The chassis runs both blocks so the modern handset uses 4G when it can and the 3G layer holds when it cannot.
The Unique Band 20 + 1 Combo: 4G Data and All-Network 3G From One Box
Across the Boost4U 100 m² range, each pair of bands covers a different service gap, and combining Band 20 with Band 1 in one chassis is the unique placement. A Band 20-only unit keeps 4G data but has no 3G fallback; a Band 8 or Band 3 unit carries a 2G call but leaves the all-network 3G layer absent. The CW100 keeps both 4G and the four-network 3G fallback in one room, which matches the household that complains of both slow 4G and a dropped call when the data bar dies.
| Layer | Band 20 800 MHz | Band 1 2100 MHz |
|---|---|---|
| Service carried | 4G LTE data | 3G UMTS data and voice |
| Uplink | 832–862 MHz | 1930–1990 MHz |
| Downlink | 791–821 MHz | 2110–2180 MHz |
| Networks | EE, O2, Vodafone, Three and MVNOs | EE, O2, Vodafone, Three and MVNOs |
| Role indoors | Fast data over distance | Call and fallback when 4G fades |
UK Network and MVNO Mapping: Which SIM Rides Which Band
The table below maps the SIM brands named on the CW100 page to their host and the layer the booster repeats. Check the SIM's host carrier rather than the shop brand, because the MVNO name itself does not appear on the tower.
| SIM brand | Host network | CW100 layer | Services in the home |
|---|---|---|---|
| EE, O2, Vodafone, Three | Own networks | Band 20 4G + Band 1 3G | 4G data, 3G fallback and voice |
| giffgaff | O2 | Band 20 4G + Band 1 3G | 4G data, 3G call and fallback |
| Tesco Mobile | O2 | Band 20 4G + Band 1 3G | 4G data, 3G call and fallback |
| Sky Mobile | O2 | Band 20 4G + Band 1 3G | 4G data, 3G call and fallback |
| Lycamobile | O2 | Band 20 4G + Band 1 3G | 4G data, 3G call and fallback |
| Talkmobile | Vodafone | Band 20 4G + Band 1 3G | 4G data, 3G call and fallback |
| Smarty, iD Mobile, Asda, BT, Plusnet, Virgin, T-Mobile, Orange, FreedomPop, The People's Operator | EE-family or listed 3G&4G roster | Band 20 4G + Band 1 3G where host reaches | 4G data, 3G fallback per host |
| Lebara, TalkTalk | Vodafone | Band 1 3G (3G-only list) | 3G call and fallback; no Band 20 4G claim |
An O2 giffgaff home sees both bands light up, a Tesco or Sky member keeps a 3G call when 4G thins, and the listed EE-family roster rides 4G plus 3G where its host reaches. In a mixed household on two or three networks, every member benefits from the same two layers, which is the practical reason the all-network Band 1 pair beats a carrier-specific voice band.
45/50dB Gain, ≥10dBm Output and the ≤5dB Noise Figure
Gain, measured in decibels, lifts the weak donor before re-radiating it; output power, in decibel-milliwatts, is the transmit level the whip radiates into the room. The CW100 carries both: ≥45 dB uplink and ≥50 dB downlink gain recover a faint rural donor, while a ≥10 dBm output spreads the recovered field across 100 m².
How gain and output divide the job
The high gain listens for the faint mast above the roof, and the modest output radiates the recovered field across the room without overwhelming the antenna isolation. Automatic gain control balances the recovered donor against the output as weather and daytime traffic change, so the LED settles rather than flaring. The ≥10 dBm level matches the 100 m², 10-user class; raising it past the class risks feeding back into the omni and does not add handsets or rooms.
Noise figure ≤5dB across 10 shared sessions
A perfect amplifier adds no noise; every real amplifier adds some, measured as the noise figure. The CW100's ≤5 dB figure keeps added noise low enough that the amplified 4G and 3G decode cleanly rather than arriving louder but garbled, which matters when up to 10 family members or staff share the space. 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.
Dual-Band CW100 vs the Band 20+8 CG100 and Band 20+3 CD100
The 100 m² range splits by tuned band at the same price, and choosing the wrong pair leaves a whole service absent indoors.
| Unit | Tuned bands | Output / users / coverage / gain | Service difference |
|---|---|---|---|
| CW100 | Band 20 + Band 1 | ≥10dBm, 10 users, 100m², 45/50dB | EE/O2/Vodafone/Three 4G plus all-network 3G |
| CG100 | Band 20 + Band 8 | ≥10dBm, 10 users, 100m², 45/50dB | O2/Vodafone 4G plus 2G calls; no all-network 3G |
| CD100 | Band 20 + Band 3 | ≥10dBm, 10 users, 100m², 45/50dB | EE+O2/Vodafone 4G; no 3G fallback or call band |
CG100: Band 8 2G voice, not all-network 3G
The CG100 keeps O2/Vodafone 4G plus a 2G circuit call on Band 8 at 900 MHz, but leaves the EE and Three layers and the all-network 3G fallback absent; an EE member or a handset that still dials 3G gets no boost on that path, even though O2/Vodafone calls work.
CD100: Band 3 4G family, no fallback band
The CD100 repeats Band 20 4G plus Band 3 to widen 4G family reach but carries neither 3G fallback nor a dedicated voice band, so when 4G fades the session drops rather than stepping down to 3G. The CW100 instead keeps the Band 1 3G leg across all four networks, which is the redundancy a thin-signal home office or cottage needs.
3G Fallback When 4G Is Unavailable, and VoLTE Where It Exists
Modern handsets prefer 4G LTE, but where the 800 MHz block cannot decode indoors or on a fringe mast, the device steps down to the 3G UMTS layer to hold a call and a slow data session. The CW100 repeats that step-down path for all four networks.
How the fallback travels on Band 1
When 4G bars vanish behind a stone wall or valley, the handset falls back to Band 1 on 1930–1990 MHz uplink and 2110–2180 MHz downlink, which the chassis repeats for EE, O2, Vodafone and Three; the call completes and a basic data link holds rather than showing no service. This matters for an older handset or a rural room where VoLTE and 4G are thin, and it is the redundancy the 4G-only CD100 cannot offer.
VoLTE where available
Where the network has enabled Voice over LTE, a modern handset places the call inside the boosted 4G Band 20 session, and the CW100 repeats that session like any other data call; the booster does not negotiate VoLTE itself, the phone and network do. Where VoLTE is off or the phone is older, the Band 1 3G fallback carries the call instead, so the household keeps talking under either route.
What the CW100 does not carry for calls
The unit does not tune 2G Band 8 at 900 MHz or Band 3 at 1800 MHz for circuit voice, so a network that still routes an older call through 2G rather than 3G receives no boost on that layer; checking whether your handset falls back to 3G or 2G before ordering avoids that gap, and neither gain nor output can invent a band the chassis does not tune.
Ofcom Licence-Exempt Status, UKCA, CE and RoHS
Four marks sit on the CW100: 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.
Ofcom licence-exempt and the permitted class
Ofcom's permitted-class rules allow a low-power fixed repeater on licensed mobile bands without the owner holding a spectrum licence. The CW100 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 10 m antenna separation is respected, and it is not modified to raise output. The ≥10 dBm figure sits inside this class rather than above it, and automatic gain control keeps the field balanced as conditions change.
UKCA, CE and RoHS
UKCA confirms the product meets applicable UK safety, electromagnetic compatibility and radio-equipment requirements for sale in Great Britain. 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, cables and adapter comply with waste-electrical rules. None of these marks alters how the bands repeat; they confirm the unit may be used without a separate permit.
Honest Limitations: No 2G Voice, No 5G, 100m² Only
A guide that lists only benefits misleads a buyer. The CW100 has three clear limits that should match your room before you order, and neither the 45/50 dB gain nor the 10 dBm output removes any of them.
No 2G voice on Band 8 or Band 3
The CW100 tunes only Band 20 and Band 1. It does not repeat 2G Band 8 at 900 MHz or Band 3 at 1800 MHz circuit voice, so an older call that drops to 2G rather than 3G receives no boost; that gap belongs to the CG100 for O2/Vodafone 2G or a Band 3 model for EE 2G.
No 5G on any band
The CW100 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 unit only lifts the 4G Band 20 layer plus the Band 1 3G layer. Expect reliable 4G data and 3G calls across the room, not boosted 5G speeds, no matter how high the gain.
100m² ceiling for one room or small flat
The rated space is 100 m² for a single room, studio, connected living room and kitchen, or a small office supporting 10 sessions; it is not a whole-house multi-floor system, and it will not blanket a separate wing, annex or large detached property. A permanently sited space clearly beyond 100 m² needs a dedicated higher-rated indoor system rather than more single-box output.
The band read: the CW100 buys the EE, O2, Vodafone or Three household both layers in one 100 m² box: Band 20 at 800 MHz for 4G via 832–862 MHz uplink and 791–821 MHz downlink, and Band 1 at 2100 MHz for all-network 3G data and voice via 1930–1990 MHz uplink and 2110–2180 MHz downlink, with ≥45/50 dB gain, a ≥10 dBm output, a ≤5 dB noise figure, 10 handsets and the omni under Ofcom licence-exempt status and UKCA, CE, RoHS; it gives the 3G fallback the data-only CD100 lacks, leaves 2G Band 8 voice to the CG100, and does not do 5G, 2G or a whole large house.
Frequently Asked Questions
Which band carries fast 4G data and which carries the 3G fallback and voice on the CW100?
Band 20 at 800 MHz carries EE, O2, Vodafone and Three LTE data over distance, while Band 1 at 2100 MHz carries the same four networks' UMTS data and circuit voice when 4G thins. Running both means the call and session do not depend on one block getting through.
In MHz, which blocks does the data carrier transmit on and listen to, and which blocks does the 3G carrier use?
The data carrier transmits on 832–862 MHz and listens on 791–821 MHz; the 3G carrier transmits on 1930–1990 MHz and listens on 2110–2180 MHz. Each paired FDD block repeats both directions together without crossing the two paths.
How do the 45/50dB gain and the 10dBm output divide the job across a 100m² room?
The ≥45 dB uplink and ≥50 dB downlink gain listen for the faint roof donor, while the ≥10 dBm output spreads the recovered field across the room without feeding back into the omni; the ≤5 dB noise figure keeps both layers legible and AGC balances the two on the move from weather to traffic.
Which hosted brands ride which host, and who appears on the 3G-only list?
giffgaff, Tesco, Sky and Lycamobile ride O2; Talkmobile rides Vodafone; the EE-family roster and the listed 3G&4G brands ride their own hosts; Lebara and TalkTalk sit on the Vodafone 3G-only list and get the fallback layer without a Band 20 4G claim.
How does the CW100 differ from the CG100 Band 20+8 in the same price range?
The CG100 repeats O2/Vodafone 4G plus a 2G Band 8 circuit call but leaves EE, Three and the all-network 3G fallback absent; the CW100 repeats 4G plus Band 1 3G across all four networks but carries no 2G call band. Pick CW100 for 3G redundancy, CG100 for O2/Vodafone 2G voice.
How does the CW100 differ from the CD100 Band 20+3 4G-only model?
The CD100 widens 4G family reach on Band 3 but carries neither 3G fallback nor a call band, so a thin 4G bar drops the session; the CW100 steps the handset down to Band 1 3G across EE, O2, Vodafone and Three when 4G cannot decode indoors.
When 4G vanishes behind a stone wall, what keeps the call alive on Band 1?
The handset falls back to the 2100 MHz UMTS block on 1930–1990/2110–2180 MHz, which the chassis repeats for all four networks; the call completes and a slow data link holds instead of showing no service. Where VoLTE exists, the modern phone talks on the boosted 4G session instead.
Does the CW100 place a VoLTE call over 4G by itself?
No; the phone and network negotiate VoLTE, and the unit only repeats the already established 4G session on Band 20. Where VoLTE is off or the handset is older, the Band 1 3G fallback carries the call, so the household keeps talking under either route.
Why can an older 2G call still fail even after fitting the CW100?
The chassis tunes Band 20 and Band 1 only; it does not repeat 2G Band 8 at 900 MHz or Band 3 at 1800 MHz. A handset that steps down to 2G rather than 3G sees that path unboosted, which is the gap the CG100 or a Band 3 model covers instead.
What do Ofcom, UKCA, CE and RoHS certify on the unit, and why does 10dBm stay legal?
Ofcom's licence-exempt class keeps the ≥10 dBm transmit level inside fixed-repeater rules with no permit fee; UKCA confirms UK radio and safety conformity, CE confirms the EU Radio Equipment Directive, and RoHS limits hazardous substances. None pushes transmit above the class, and 100 m² for 10 sessions is the line before a whole-house system.
Learn More: CW100 Guides & Comparisons
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