The short answer first: in a large UK home of 150-250 m², the most reliable way to get better 4G signal on EE, O2, Vodafone and Three is to install a 70 dB Band 20 (800 MHz) mobile signal booster such as the Boost4U C200 at £169.99. It pulls in the weak outdoor signal, amplifies it by up to 70 dB, and rebroadcasts it through a 7 dBi panel antenna across up to 200 m² (2,153 sq ft), supporting up to 20 simultaneous users.

This guide walks through exactly why large homes lose signal, compares six possible fixes, explains the dB math, the Ofcom rules, Band 20 propagation, antenna choice, installation and troubleshooting, and ends with the running costs. By the end you will know whether the C200 is the right 200 m² 4G booster for your property.

Before spending money, it helps to know where the signal is actually going. A 4G radio link from the mast to your phone loses strength in three distinct ways, and large homes suffer all three at once.

1. Free-space path loss with distance

The 4G signal weakens predictably the further it travels. The free-space path loss formula is FSPL(dB) = 20log₁₀(d) + 20log₁₀(f) + 32.44, where d is distance in km and f is frequency in MHz. At 800 MHz, doubling the distance adds roughly 6 dB of loss. A mast 2 km away already costs about 98 dB; at 5 km that rises to about 106 dB before the signal even reaches your roof.

2. Building-material penetration loss

Once the signal reaches the house, each wall, floor and roof layer absorbs more energy. Double glazing, cavity walls, reinforced concrete and slate roofs are the worst offenders. The table below shows typical one-way penetration loss at 800 MHz.

3. Fresnel-zone obstruction

Radio waves do not travel in a straight line between mast and phone; they use an ellipsoidal "Fresnel zone" around the line of sight. Even if you can see the mast, trees, chimneys, neighbouring roofs and upper floors inside that ellipse add diffraction loss. In a two- or three-storey house, the back bedroom on the top floor is often deep inside the obstruction shadow, which is why it shows one bar while the front lounge shows four.

A flat or small 90 m² bungalow only has to beat one or two walls. A large detached house stacks up three problems at once.

Single-room coverage is not whole-home coverage. A basic 50 dB booster might give you four bars in the room where the panel antenna sits, but the signal falls off by roughly 10-15 dB per wall as it spreads. By the time it reaches the far end of a 12 m open-plan extension, it is back to one bar.

Multi-floor attenuation compounds the loss. A concrete floor slab costs another 10-15 dB on top of the walls. Ground-floor signal rarely reaches the first bedroom; first-floor signal rarely reaches the basement or garage conversion.

More internal walls mean more cumulative loss. A typical 200 m² detached house has 8-12 internal partitions between the front-facing room and the kitchen or study. Even at a modest 6 dB per wall, that is 48-72 dB of total indoor loss — more than most small boosters can compensate for.

There is more than one route to better signal, but only one of them actually strengthens the cellular radio link itself. Here is the honest comparison for a 150-250 m² UK house.

Pros of the booster route: it is the only option that improves the actual cellular signal for every phone, tablet and mobile router in the house, works on all four networks simultaneously, and costs a single £169.99 rather than a recurring bill.

Cons of the booster route: it needs 20-25 minutes of DIY work and a suitable outdoor mounting point. If your broadband is your only problem, a booster will not make your internet faster beyond the 4G link itself.

A booster does not create signal from nothing. It repeats the existing outdoor signal in three clean steps.

Step 1 — Capture. The outdoor omni antenna picks up the faint Band 20 signal coming from the nearest EE, O2, Vodafone or Three mast. Even at -100 dBm it is still a usable carrier.

Step 2 — Amplify. The weak signal travels down the 10 m 5D-FB coax to the main unit, which raises it by up to 70 dB. AGC (automatic gain control) then trims that gain in real time so the booster never overloads and never feeds oscillation back into the mast.

Step 3 — Rebroadcast. The cleaned-up signal is sent to the indoor 7 dBi panel antenna, which radiates it across the home. Your phone sees a strong -65 to -75 dBm signal and shows four bars.

The dB gain math, in plain terms

Every 3 dB doubles the power. Moving from 60 dB to 70 dB is 10 dB, which is just over 3x more output. Combined with the 20 dBm maximum output power (EIRP), the C200 has enough headroom to drive a 7 dBi panel antenna across a 200 m² floorplate without distortion. Its ≤4 dB noise figure means weak signals stay clean rather than being amplified along with the hiss.

Why AGC matters

Without automatic gain control, a booster with a strong outdoor signal would self-oscillate — the indoor antenna would feed the outdoor antenna, causing whistling and interference that Ofcom forbids. The C200's AGC continuously lowers gain when the outdoor signal is strong and raises it when weak, which is exactly the technical condition Ofcom requires for a licence-exempt booster.

Gain and coverage area are not the same thing, but they track closely once you account for indoor wall loss. The table below is a realistic rule of thumb for a typical British detached house on Band 20.

The C200 sits exactly on the 70 dB line. That is deliberate: 70 dB is the sweet spot for a large UK family home — enough to push through 8-12 internal walls without paying enterprise-level prices for 80 dB hardware you would never fully use.

Ofcom updated its expectations for licence-exempt repeaters in the UK, and the rules are stricter than many buyers realise.

Legal boosters must: carry Ofcom licence-exempt certification, include automatic gain control (AGC), limit output to the permitted EIRP, and only amplify bands actually used by UK operators. The Boost4U C200 meets all four conditions.

Illegal boosters: cheap unbranded units sold on marketplaces often lack AGC, overshoot EIRP and cause interference to the mobile network. Ofcom has the power to fine operators of illegal transmitting equipment up to £5,000 and can require the equipment to be removed.

The band test: a booster that amplifies Band 12/17 (700 MHz, US) is not doing anything useful on UK networks, because EE, O2, Vodafone and Three carry their wide-area 4G on Band 20 (800 MHz). Buying the right band is part of staying legal and useful.

Band 20 is the 800 MHz FDD LTE band that all four UK operators share for long-range, in-building 4G coverage. Its low frequency travels further and penetrates walls better than the higher bands used for capacity.

Because Band 20 is already the universal "coverage band" in the UK, a single-band booster like the C200 is not a compromise — it is a targeted tool aimed at the exact frequency that reaches the longest distance and goes through the most walls. In a large home, that wall-penetration advantage is worth more than multi-band flexibility you will never use.

The indoor antenna choice changes how the signal spreads inside a large home. A small whip radiator and a flat panel antenna behave very differently.

The C200's 7 dBi panel antenna is the single most important reason it reaches 200 m² while a 3 dBi whip tops out near 100 m². Aim the panel at the busiest living area — typically the hallway, landing or open-plan lounge — and the signal radiates through the doors rather than fighting walls.

The C200 is designed for DIY. No engineer call-out, no drilling beyond a couple of wall brackets. The six steps below assume a typical two-storey detached house.

1. Find the best outdoor spot. Walk outside and check where the phone shows the strongest Band 2G signal, usually on the chimney stack or the gable end facing the mast. Mount the 7 dBi omni outdoor antenna at roofline height.

2. Run the cable indoors. Feed the 10 m 5D-FB coax through a soffit, window gland or drilled hole into the room nearest the roof. The standard 10 m is enough for most homes; 20/30/40/50 m upgrades are available for far-away living rooms.

3. Mount the indoor panel antenna. Fix the 7 dBi panel on an inside wall in the central hallway or landing, facing the rooms you use most. Keep it away from metal appliances.

4. Respect the 10 m separation. The indoor and outdoor antennas must be at least 10 m apart vertically (ideally one above the other with the roof in between). If they are too close, the booster self-oscillates and AGC cuts the gain to near zero.

5. Connect and power on. Plug the outdoor cable into the "BTS" port and the indoor panel into the "MS" port, then plug in the 12 W power adapter. The LEDs show lock and gain status.

6. Verify on your phone. Stand in the kitchen, the upstairs bedroom and the garden office and check the bars. Re-aim the panel by 10-15 degrees if one room is still weak.

Phone bars are a rough guide. The dBm number is the real measurement. The table below translates the readings most large-home users will see.

On iPhone: open the Phone app and dial *3001#12345#*, then tap Serving Cell Info to see the RSRP reading. On Android: Settings > About phone > Network > SIM status, or use the free Network Cell Info Lite app. Before the C200, a typical kitchen reads -95 to -105 dBm; after installation the same room reads around -65 to -75 dBm.

The C200 is engineered for exactly this use case. It is not a scaled-up C100; it is a different device aimed at larger homes.

Key specifications

Band: Band 20 / 800 MHz FDD LTE. Uplink: 832-862 MHz. Downlink: 791-821 MHz. Maximum gain: up to 70 dB. Output power: 20 dBm EIRP. Coverage: up to 200 m² (2,153 sq ft). Noise figure: ≤4 dB. Power: ≤12 W. Users: up to 20 simultaneously. VoLTE: supported. AGC: yes. Size: 180 × 120 × 28 mm, ~550 g. Indoor antenna: 7 dBi panel. Outdoor antenna: 7 dBi omni. Cable: 10 m 5D-FB, upgradeable to 50 m. Price: £169.99.

Pros

Pros:
✓ 70 dB gain and 20 dBm output are matched to a 200 m² floorplate.
✓ 7 dBi panel antenna radiates further than a 3 dBi whip.
✓ ≤4 dB noise figure keeps weak signals clean.
✓ AGC keeps the unit Ofcom-legal and oscillation-free.
✓ Up to 20 simultaneous users covers a large family plus smart-home devices.
✓ VoLTE supported, so HD voice calls stay clear.
✓ 365-day refund guarantee and free UK delivery in 10-15 days.

Cons

Cons:
✗ Single-band (Band 20 only); if your mast only broadcasts on Band 3/7 in your street, it will not help.
✗ 10 m standard cable; far-flung outbuildings need a 20-50 m upgrade.
✗ No app or LCD; tuning is done by phone dBm readings.
✗ Best for homes where the outdoor signal is at least -95 to -100 dBm; weaker sites need the Yagi upgrade.

Most "booster does not work" stories are install mistakes, not hardware faults. Check these six first.

1. Uplink and downlink ports reversed. The outdoor cable must go to "BTS" (toward the mast) and the indoor panel to "MS" (toward phones). Swapped, the unit will not lock.

2. Antennas too close. If the indoor panel is within 10 m of the outdoor antenna, AGC drops gain to zero. Move the indoor unit to the opposite side of the house or put a floor/roof between them.

3. Cable loss on long runs. A 30 m 5D-FB run loses roughly 9 dB at 800 MHz, which can eat half your gain. For long runs upgrade to LMR400 or accept the trade-off.

4. Sharing a power strip with a router or microwave. Switch-mode power supplies inject noise onto the coax. Plug the C200 into a wall socket on its own.

5. Wrong outdoor orientation. An omni antenna is forgiving, but if you upgrade to a Yagi, pointing it 20 degrees off the mast costs 3-6 dB. Use a cell tower map to aim it.

6. No re-test after building work. A new extension, loft insulation with foil backing or a replacement slate roof can add 10-15 dB of loss. Re-measure the dBm after any structural change and re-aim the panel.

One question comes up constantly: "will this raise my electricity bill?" The C200 draws a maximum of 12 W, and in practice it averages around 8-10 W because AGC trims the amplifier once the signal is locked.

At a typical UK electricity price of around 34p/kWh, 12 W running 24/7 costs roughly £12-18 a year — less than a single takeaway. Against a new phone contract at £25/month, the C200 pays for itself within about eight months and then improves signal for every device in the house for years.