The CD200 shares the same Band 20+3 dual bands and ≥60/≥65 dB gain but outputs ≥10 dBm and covers up to 200 m² for 20 users; the CD250 keeps the same gain but raises output to ≥17 dBm and reaches 250 m² for 25 users. The C250 is a single Band 20 (800 MHz) unit that boosts O2/Vodafone 4G but misses EE Band 3 4G and voice. Choose the CD250 for a medium home, small office or café where 250 m² and 25 users matter; step down to the CD200 for 200 m², and choose the C250 only if you are O2/Vodafone-only and do not need EE.

Band 20 (800 MHz) is the rural propagation band used by O2 and Vodafone for 4G, reaching further over distance and through obstacles; Three 4G rides Band 20 over the shared O2 MOCN. Band 3 (1800 MHz) carries EE 4G alongside the EE 2G GSM layer for calls and SMS. The CD250 amplifies both simultaneously, so an O2 phone and an EE phone in the same premises both get boosted 4G without switching boxes.

Up to 250 m² (2,691 ft²) means a medium three-bedroom terraced or semi home, a compact detached, a small office, or a café/small pub dining room. It is not a whole-house solution for a large detached, three-storey or sprawling commercial premises; the 4-star review from Lisa P. notes it covers the living room and kitchen but a bigger model would be needed for the whole house. Solid walls, metal shelving and distance from the whip shrink the usable area.

The CD250 supports up to 25 phones or data devices connected at the same time, sharing the boosted Band 20 and Band 3 capacity. This suits a small office team, a busy family home, or a café/small shop floor. Beyond 25 active users the shared RF capacity thins out; a large open-plan office or full pub needs a higher-capacity distributed system. It is connected capacity, not a guaranteed 25 fast-speed lines at once.

Gain in dB measures how much the amplifier strengthens the signal: ≥60 dB uplink lifts your phone's signal back up to the mast, and ≥65 dB downlink lifts the mast's signal down to your phone. Output in dBm measures the final radiated strength: ≥17 dBm is about 50 mW, roughly five times the CD200's ≥10 dBm (≈10 mW), and that higher radiated power is what reaches across 250 m². Gain and output work together — high gain without enough output still leaves corners weak.

The CD250's higher ≥17 dBm output is the hardware difference that covers a larger 250 m² space; both models share the same ≥60/≥65 dB gain, so the extra coverage comes from radiated power, not more amplification. The unit remains in the Ofcom licence-exempt mobile repeater class; it is not a licensed high-power outdoor transmitter. Choose CD250 for the bigger footprint, CD200 for 200 m² where the higher output is unnecessary.

The supplied 5 dBi omni works well when you have a clear, unobstructed mounting spot with 1–2 bars outside and do not need to aim at a specific mast. Where donor signal is very weak, or the mast lies in one direction behind a ridge or trees, the paid high-gain directional aerial (+£50) focuses the pickup on that mast and often makes the difference between marginal and solid. Start with the omni, read the bar count, and upgrade only if signal stays weak.

At least 1–2 bars of usable outdoor signal on Band 20 and/or Band 3 at the omni mounting point, checked with a phone outside on the wall, roof or eave. A booster amplifies the donor signal it receives; it cannot create signal where none exists outside. If your phone shows zero bars and emergency calls only even at the mounting point, this unit will not work, and neither will any Ofcom-legal booster at this price.

The CD250 carries a 365-day money-back guarantee: if it does not work for your location, return it by mail within 365 days for a refund; return shipping is deducted from the refund (ReturnShippingFees), so it is not a free-return label. Standard delivery is free: handling takes 1–2 working days and UK transit 10–15 working days, so it is not next-day, and the same policy covers 15 European countries (GB, DE, FR, IT, ES, NL, BE, AT, SE, DK, FI, IE, PT, PL, CZ).

The CD250 boosts 4G LTE data and 2G calls/SMS; calls over 4G work when your handset and network offer VoLTE (Voice over LTE), which O2, Vodafone, EE and Three support on compatible plans. It does not boost 5G NR on any band and it does not boost 3G UMTS Band 1 (2100 MHz), so a device stuck on 3G fallback will not be helped. If 5G speed or 3G fallback is the main requirement, a different unit on those bands is needed.