CW250 Band 20 + 1 Explained: How the 250m² Dual-Band Booster Delivers 4G LTE Data and 3G All-Networks in UK Homes and Small Offices
The Boost4U CW250 repeater repeats two UK layers across a three-bedroom house, large flat, cottage, home office, cafe 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 ≥60 dB uplink and ≥65 dB downlink gain with a ≥17 dBm output about five times the radiated power of a 10 dBm unit, a ≤5 dB noise figure, a 5 dBi omni and a 3 dBi whip to cover up to 250 m² for 25 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 the same 60/65 dB gain plus the higher 17 dBm output amplify both across 250 m², which UK networks and MVNOs ride which band, how the CW250 compares with the CW200, the Band 20+8 CG250 and the Band 20+3 CD250, 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 250 m² only.
Answer first: the CW250 is the 250 m² Band 20+1 repeater: 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 ≥60/65 dB gain, a ≥17 dBm output, a ≤5 dB noise figure, 25 handsets and the omni outside. It suits the household, small office or cafe that spreads over three rooms, 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 250 m² 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 CW250 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 home, with the omni catching the donor above the roof and the 65 dB downlink gain plus the 17 dBm output spreading it over 250 m².
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 CW250 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 gain and the stronger output spread it across the rooms.
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 CW250 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 home even where the Band 20 4G layer is weak. This is the feature that separates CW250 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, and the 17 dBm output reaches the third bedroom or the cafe back room.
The Unique Band 20 + 1 Combo: 4G Data and All-Network 3G From One Box
Across the Boost4U 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 CW250 keeps both 4G and the four-network 3G fallback in 250 m², 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 CW250 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 | CW250 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 a Lebara user on the Vodafone fallback list keeps calls on Band 1; 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.
≥60/65dB Gain, ≥17dBm Output and the Headroom Over the CW200
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 home. The CW250 carries both: the 60/65 dB gain recovers the faint rural donor, while the ≥17 dBm output spreads the recovered field across 250 m² with three antennas.
What +7dBm over the CW200 means in radiated power
The CW200 runs the same 60/65 dB gain at a 10 dBm output; the CW250 keeps the gain but raises output to 17 dBm. Each +3 dB roughly doubles the radiated power, so +7 dBm lands near five times the field of a 10 dBm box. That extra power is what feeds a third whip through the 3-way splitter and reaches the third bedroom or cafe back room rather than fizzling after two antennas. Raising output does not raise gain or tune new bands; automatic gain control balances recovered donor against the stronger output as weather and traffic change.
Noise figure ≤5dB across 25 shared sessions
A perfect amplifier adds no noise; every real amplifier adds some, measured as the noise figure. The CW250'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 25 family members, staff or cafe customers 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.
CW250 vs CW200, and the Band 20+8 CG250 and Band 20+3 CD250
The range splits by tuned band, gain, output, area and users, and choosing the wrong model leaves either a service gap or unused budget.
| Unit | Tuned bands | Gain / output / users / area / antennas | Service difference |
|---|---|---|---|
| CW250 | Band 20 + Band 1 | ≥60/65dB, ≥17dBm, 25 users, 250m², 3 antennas | EE/O2/Vodafone/Three 4G plus all-network 3G |
| CW200 | Band 20 + Band 1 | ≥60/65dB, ≥10dBm, 20 users, 200m², 2 antennas | Same bands and gain, lower output and one fewer antenna |
| CG250 | Band 20 + Band 8 | ≥60/65dB, ≥17dBm, 25 users | O2/Vodafone 4G plus 2G calls; no all-network 3G |
| CD250 | Band 20 + Band 3 | ≥60/65dB, ≥17dBm, 25 users | EE+O2/Vodafone 4G; no 3G fallback or call band |
CW200 to CW250: same bands and gain, +7dBm output, +50m², +5 users, 3 antennas
The CW200 repeats the identical Band 20+1 services at the same 60/65 dB gain but on a 10 dBm output for 200 m² and 20 users with two indoor antennas; the CW250 keeps the bands and gain but adds 7 dBm of output, about five times the field, spreads over 250 m² for 25 handsets, and supports three antennas through the 3-way splitter. Pick CW200 for a two-bedroom flat, CW250 for a three-bedroom house or cafe; neither changes which services are carried.
CG250: Band 8 2G voice, not all-network 3G; CD250: Band 3 4G family
The CG250 keeps O2/Vodafone 4G plus a 2G circuit call on Band 8 at 900 MHz, but leaves EE, Three and the all-network 3G fallback absent; the CD250 repeats Band 20 4G plus Band 3 to widen 4G family reach but carries neither 3G fallback nor a dedicated voice band. The CW250 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 CW250 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 CD250 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 CW250 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 CW250 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 the 17 dBm output nor the 60/65 dB gain can invent a band the chassis does not tune.
Ofcom Licence-Exempt Status, UKCA, CE and RoHS
Four marks sit on the CW250: 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 60/65 dB gain or the 17 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 CW250 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 ≥17 dBm figure sits inside this class rather than above it, and automatic gain control keeps the field balanced as conditions change; the higher output is a permitted step within the class, not a modification.
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, 250m² Only
A guide that lists only benefits misleads a buyer. The CW250 has three clear limits that should match your home before you order, and neither the 60/65 dB gain nor the 17 dBm output removes any of them.
No 2G voice on Band 8 or Band 3
The CW250 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 CG250 for O2/Vodafone 2G or a Band 3 model for EE 2G.
No 5G on any band
The CW250 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 250 m², not boosted 5G speeds, no matter how high the output.
250m² ceiling for a three-bedroom house
The rated space is 250 m² for a three-bedroom house, large connected flat, small office or cafe supporting 25 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 250 m² needs a dedicated higher-rated indoor system rather than more single-box power.
The carrier read: the CW250 buys the EE, O2, Vodafone or Three household both layers in one 250 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 ≥60/65 dB gain, a ≥17 dBm output about five times the CW200's field, a ≤5 dB noise figure, 25 handsets, three whips through the splitter and the omni under Ofcom licence-exempt status and UKCA, CE, RoHS; it adds 7 dBm, 50 m², five users and a third antenna over the CW200, leaves 2G Band 8 voice to the CG250, and does not do 5G, 2G or a whole large house.
Frequently Asked Questions
Which band carries fast 4G data and which carries the all-network 3G fallback on the CW250?
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 across the 250 m² space.
List the send and receive MHz windows the chassis amplifies, separately for the 4G carrier and the 3G carrier.
The 4G block transmits on 832–862 MHz and tunes to 791–821 MHz; the 3G block transmits on 1930–1990 MHz and tunes to 2110–2180 MHz. Each paired FDD window carries both directions together without crossing the two paths inside the home.
How do the 60/65dB gain and the 17dBm output divide the job across a three-bedroom house?
The gain listens for the faint roof donor above the slab and brick, while the stronger 17 dBm field spreads the recovered signal over three rooms and feeds a third whip; the ≤5 dB noise figure keeps both layers legible and AGC balances them as weather and traffic change.
What does the extra 7dBm over the CW200 actually do to the field and the antenna count?
Each +3 dB doubles radiated power, so +7 dBm lands near five times the CW200's 10 dBm field; that extra headroom is what lets the 3-way splitter drive three whips across 250 m² instead of two on 200 m², with the same 60/65 dB gain and bands.
Which O2-hosted and Vodafone-hosted shop brands get both bands, and which two only get the fallback leg?
giffgaff, Tesco, Sky and Lycamobile ride O2, while Talkmobile rides Vodafone, and the EE-family roster rides its own host; Lebara and TalkTalk sit on the Vodafone fallback-only leg and receive the Band 1 layer without a Band 20 4G claim across the house.
How does the CW250 differ from the CG250 Band 20+8 at the same price and area?
The CG250 repeats O2/Vodafone 4G plus a 2G Band 8 circuit call but leaves EE, Three and the all-network 3G fallback absent; the CW250 repeats 4G plus Band 1 3G across all four networks but carries no 2G call band. Pick CW250 for 3G redundancy, CG250 for O2/Vodafone 2G voice.
How does the CW250 differ from the CD250 Band 20+3 4G-only model?
The CD250 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 CW250 steps the handset down to Band 1 3G across EE, O2, Vodafone and Three when 4G cannot decode indoors.
When the 4G bar dies behind a stone wall, how does the handset fall back across the 250 m² house?
The device steps down 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 CW250 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.
Which circuits stay unboosted because the chassis skips Band 8 and Band 3, and which stamps authorise the 17dBm level?
Because the box tunes only Band 20 and Band 1, a handset that steps down to 2G on Band 8 or Band 3 sees that path unboosted; Ofcom's licence-exempt class admits the 17 dBm level without a fee, UKCA confirms UK conformity, CE the EU directive, and RoHS restricts hazardous substances.
Learn More: CW250 Guides & Comparisons
Best 3G+4G Signal Booster UK (250m²) — 2026 Guide
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CW250 vs CW200 vs CG250
Honest UK comparison of Band 20+1 (250m² 25-user ≥17dBm 3-antenna) against CW200 (200m²) and Band 20+8 O2/Vodafone 2G voice at £295.00.
Mobile Booster Installation Guide (250m²)
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Band 20+1: 4G & 3G All-Networks Explained
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