The CD100 covers the same Band 20+3 dual bands but at up to 100 m² for 10 users with lower gain, so it suits a single room or small bedsit; the C200 is a single Band 20 (800 MHz) unit that boosts O2/Vodafone 4G but misses EE Band 3 4G and voice. The CD200 keeps both bands, steps up to 200 m² for 20 users and raises gain to ≥60 dB uplink / ≥65 dB downlink. Choose the CD200 for a small flat, 2-bed house or home office with mixed operators; step down to the CD100 only for a single room, and choose the C200 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 CD200 amplifies both simultaneously, so an O2 phone and an EE phone in the same home both get boosted 4G without switching boxes.

Up to 200 m² (2,153 ft²) means a small flat, a 2-bed terraced or semi home, a cottage living room plus kitchen and bedroom, or a home office / compact shop. It is not a whole-house solution for a large detached, three-storey or sprawling property; 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 CD200 supports up to 20 phones or data devices connected at the same time, sharing the boosted Band 20 and Band 3 capacity. This suits a small family, a compact home office with a handful of staff phones, or a small reception/shop counter. Beyond 20 active users the shared RF capacity thins out; a busy shop floor or a whole team needs a higher-capacity unit. It is connected capacity, not a guaranteed 20 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 — about 15 dB more amplification than the smaller CD100, which is what reaches across 200 m². Output power in dBm measures the final re-broadcast strength; the CD200 caps at ≥10 dBm (about 10 mW) under Ofcom's licence-exempt limit. That is plenty for 200 m² indoors but deliberately lower than a high-power repeater.

UK licence-exempt mobile repeaters are restricted to a low maximum output (≥10 dBm per this unit's class) to protect the mobile network from interference; the Wireless Telegraphy (Mobile Repeater) Exemption framework sets these bounds so no operator licence or paid spectrum authorisation is needed. A higher-output amplifier would require licensing and is not what the CD200 is designed for. The trade-off is that it is legal, plug-and-play and low-cost, but confined to a small-to-mid indoor area.

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 CD200 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 CD200 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.