Because the GD250 boosts Band 3 (1800 MHz), which is the 4G LTE band that EE and Three use — but O2 and Vodafone carry most of their UK 4G traffic on Band 20 (800 MHz), a lower frequency this unit does not cover. So an O2 or Vodafone SIM in a GD250-boosted home will show full bars for calls and SMS on Band 8 (900 MHz), but your 4G mobile data will not be amplified. If you are an O2 or Vodafone customer who needs faster 4G data indoors, you need a Band 20 (800 MHz) booster, not the GD250. The GD250 is the right choice if your pain point is dropped calls and failing texts on O2/Vodafone, or if you have an EE or Three data SIM in the same building.

Three has switched off its 2G GSM network across most of the UK — Three phones never had a 2G voice fallback in the way EE, O2 and Vodafone phones do. The GD250 boosts Band 8 (900 MHz) 2G voice, but Three does not transmit 2G voice on that band, so a Three SIM gets no call amplification. What Three does carry on Band 3 (1800 MHz) is 4G LTE data — and that is exactly what the GD250 boosts. So Three customers see fast 4G data indoors but calls still rely on Three's own 4G VoLTE coverage. If you are a Three customer whose pain is dropped calls rather than slow data, the GD250 will not fix voice; it will fix mobile data.

Buying both single-band units separately costs £279 — £44 more than the GD250 at £235 — and leaves you with two amplifiers, two power supplies, two indoor antennas and two drill kits to route and mount. The GD250 combines Band 8 voice and Band 3 data in one chassis, one LED panel, one 10 m coax and one UK 3-pin adapter. It is the better buy if you need both bands in the same building. If you only need O2/Vodafone calls, the G250 at £110 is enough; if you only need EE 4G, the D250 at £169 is enough. The GD250 exists for the mixed-carrier household or small premises that would otherwise have to buy two boxes.

Yes — EE is the one UK carrier that runs both 2G voice on Band 8 (900 MHz) and 4G LTE data on Band 3 (1800 MHz), so an EE SIM is fully covered by the GD250: calls, SMS and mobile data are all amplified simultaneously. This is why the GD250 is described as "all four operators" — it covers all four carriers in the sense that it amplifies the bands each carrier uses, but only EE receives both voice and data from this one unit. If everyone in your household is on EE, the GD250 is the most complete single-unit solution Boost4U sells for a 250 m² home.

A Yagi antenna is highly directional: it receives best when the long axis of the antenna points directly at the base station you want. The 8 dBi gain comes from that focus — about 3–4 dB more than a basic omni antenna — but if you point it at the wrong mast or at a solid brick chimney, you will see little or no improvement. Use a free field-strength app on your phone, walk outside the mounting point, find the direction where Band 8 and Band 3 signal is strongest, and aim the Yagi's elements along that bearing. The weatherproof bracket lets you fine-tune the angle after mounting. If your donor signal is already strong outside, an omni antenna would work — but in fringe rural signal, the Yagi's directionality is what makes the 50/55 dB gain usable across 250 m².

At least 10 m of vertical separation — ideally the Yagi on the roof or gable and the indoor panel antenna on a lower floor or in a ground-floor room — is the rule of thumb for this gain level. "Self-oscillation" (or feedback) happens when the indoor antenna's re-broadcast signal is picked up directly by the outdoor antenna, creating a loop that overloads the amplifier and can interfere with the carrier's network. AGC helps, but it cannot fully cancel a tight loop. If you only have a two-storey house, place the indoor antenna in the centre of the lower floor and make sure it faces away from the Yagi's direction. The LED indicators on the GD250 will show an overload warning if the separation is too small.

No on all four. The GD250 is a dual-band unit fixed to Band 8 (900 MHz) and Band 3 (1800 MHz). It will not boost 5G NR on any band, it will not boost 3G UMTS, it will not boost O2/Vodafone 4G on Band 20 (800 MHz), and it will not boost EE/Vodafone 4G on Band 7 (2600 MHz). If your phone shows a 5G icon outdoors and you want 5G indoors, this is the wrong product. If your O2/Vodafone 4G is slow indoors because it rides Band 20, you need a Band 20 booster. The GD250 is the correct product only if your pain is Band 8 2G calls and/or Band 3 1800 MHz 4G data.

Yes, and this is the exact use case the GD250 was built for. The EE phone gets amplified 2G calls on Band 8 and amplified 4G data on Band 3. The O2 phone gets amplified 2G calls and SMS on Band 8, with its 4G data left as-is (O2 4G on Band 20 is not touched). Both phones benefit at the same time because the GD250 amplifies both bands continuously — it does not switch between them. Up to 25 devices can be connected at once. This is why the GD250 costs more than a single-band unit: it is solving a multi-SIM, multi-carrier problem in one box.

For a corner shop, a small office or a neighbourhood café, yes — 25 concurrent users covers staff plus a typical number of customers on their own phones at any one time. For a busy pub with 50+ patrons at a weekend, a 50-desk open-plan office, or a warehouse with staff across two floors, 25 will be too few and you should step up to a commercial C-series unit. The cap is a hard limit built into the RF design; it is not a soft licence. If you are unsure, count how many phones, tablets and mobile hotspots are actively using mobile data or making calls during your busiest hour — if that number stays under 25, the GD250 is the right size.

A signal booster amplifies the donor signal it receives at the outdoor antenna — it does not create radio waves from nothing. If your phone shows zero bars and "Emergency calls only" when you stand outside your front door, no Ofcom-legal booster at this price can manufacture a Band 8 or Band 3 signal. The GD250 is tuned for the very common UK scenario where you can get 1–2 bars outside (on the roof, chimney or gable) but the concrete, brick, cavity wall and double glazing drop you to zero or one bar indoors. The 8 dBi Yagi on the roof picks up that weak-but-present 1–2 bars and the 50/55 dB gain re-broadcasts it as a strong indoor signal. Before ordering, stand outside your mounting point and check Band 8 and Band 3 field strength in your phone's field mode or a network-scanner app.