Answer first: the CG100 is a plug-and-play dual-band repeater for a single room, small flat or home office up to 100 m², repeating Band 20 at 800 MHz for O2, Vodafone and Three 4G data and Band 8 at 900 MHz for O2 and Vodafone 2G voice calls and SMS. The whole job breaks into ten factual steps: (1) read the outdoor 4G signal in dBm at the wall before mounting; (2) fix the 5 dBi omni to the roof, eaves or a high clear wall; (3) lay the included 10 m coax through the loft or a sealed cable route; (4) hold the outdoor omni and the indoor whip at least 10 m apart vertically; (5) connect the outdoor cable to the BS donor port and the whip to the MS server port; (6) plug the 5 V DC adapter in last; (7) let the automatic gain control warm up for 3 to 5 minutes; (8) read the steady green band LEDs; (9) test a 4G session and a normal call from the driver of each zone; (10) confirm the setup holds across 10 users before leaving the magnet or bracket alone on a rural rooftop.

CG100 Snapshot Before You Start Fixing the Outdoor Antenna

A short spec table keeps every number this guide relies on in one place. The CG100 delivers uplink gain of at least 45 dB and downlink gain of at least 50 dB on both bands, a maximum output of at least 10 dBm, a noise figure no higher than 5 dB, and a rated indoor space of up to 100 m² for up to 10 active sessions.

Step 1: Read the Outdoor 4G Signal in dBm at the Wall Before Mounting

A home repeater can only amplify the signal the outdoor antenna actually receives; brick, reinforced concrete, metal fascias and a tiled roof all hide the tower from a handheld phone. The pre-mount check happens on foot beside the house, not on the sofa, and it decides where the omni sits and whether the included aerial is enough or the optional Yagi earns its keep.

The dBm ranges the CG100 expects at the outdoor antenna

-97 dBm on 4G reads as a healthy rooftop donor that the ≥50 dB downlink gain and ≥10 dBm output can turn into a usable indoor signal. -105 dBm sits at the edge of the recommended band and still produces a stable data session once the omni clears the wall, but the margin absorbs aerial loss, tinted glass and the pitch side shelter more comfortably than a phone held to the kitchen window. -112 dBm on 4G is the practical floor: roughly -112 dBm the LTE receiver loses the control channel, the phone falls back to a slower service or shows no service, and no booster manufactures a donor the outdoor antenna never receives. The ≥45 dB uplink gain recovers a weak outdoor donor better than holding a phone to the glass, but it cannot invent a band the survey never picked up.

How to read dBm rather than bars in a home survey

Phone bars are subjective and differ between iPhone and Android; the dBm figure is the measurement the amplifier actually sees. On an iPhone, enter field-test mode from the dialler and watch the RSRP value while standing beside the house. On Android, use the engineering or network diagnostics menu, or a free field-test app that lists RSRP by band. Hold the phone away from your body, because a hand and head absorb 3 to 5 dB, and read the value on the side of the house facing the nearest mast rather than the sheltered courtyard side.

Where to survey: roadside, side wall, campsite pitch, motorway layby

Stand on the roof-facing side of the house, the open field side at the rear, and the far side of the driveway; record the reading for your own SIM and a member of the household on a different network, because the strongest combined spot is where the omni goes. On a rural lane the open gable or roof edge usually beats the side sheltered by a hedge or a barn; on a town house the hard side facing the street typically beats the enclosed courtyard. Survey warning: if your Band 20 reads below -112 dBm at every position beside the house, the CG100 cannot manufacture that band inside. You may still improve voice on the other network's service, but the missing 4G stays missing; in that case re-check facing the proper mast rather than expecting the amplifier to close the gap by itself.

Step 2: Mount the 5 dBi Omni-Directional Antenna for an Open Horizon

The 5 dBi omni outdoor antenna gathers signal equally from all horizontal directions rather than focusing one narrow beam, which suits a home where the usable O2 or Vodafone mast can sit in any compass direction. On a tiled or slated roof it fixes without drilling tiles; on a chimney stack, gable wall or fascia it uses the supplied bracket; on a flat roof the weighted base or adhesive pad settles the omni in clear air.

Roof edge or gable: clear sky line over 3 to 5 metres height

Wipe the roof or stack clean, peel the adhesive pad or bolt the small bracket, and press or fix the omni to the roof edge, chimney breast or gable, away from roof rails, satellite dishes, vent pipes and the TV aerial. Keep the omni at least 3 metres above any roof-mounted clutter, ideally 3 to 5 metres up, because metal near the base absorbs the 5 dBi pickup. The roof-edge position favours an all-round donor on a rural lane; the central ridge position balances all directions for a town house. Keep the omni at least a metre clear of roof-mounted air horns, spotlights and satellite dishes, because metal near the base defeats the omni pickup.

Solid chimney, rendered wall or fascia: bracket rather than suction

A suction cup holds on a smooth tiled roof for short jobs but weathers; a permanent fix uses the small screw bracket on a brick gable, chimney stack or painted fascia. Drill a 6 mm pilot hole through the rendered wall, fit the wall plug, screw the bracket level, then clip the omni onto it. Never rely on an adhesive pad on a windy exposed ridge without the bracket as backup. The omni points straight up by design; do not tilt it toward the mast unless you have switched to the directional Yagi, because tilting an omni cancels part of its circular pattern.

When the omni falls short: the optional high-gain Yagi

Where the donor sits at -105 to -112 dBm on one identifiable mast, the omni's all-round pattern wastes half its pickup in open sky; the optional high-gain Yagi focuses a narrow beam straight at that tower and recovers several decibels more. This is the weak-donor upgrade, not a requirement for a normal suburban home, and this guide returns to the Yagi trigger in the rural optimisation section below.

Step 3: Route the Supplied 10 m Low-Loss Coax and Choose a Cable Upgrade

The included 10 m outdoor low-loss coaxial cable carries the recovered donor from the roof to the booster unit, and its loss changes every metre. Low-loss cable keeps the ≥45 dB uplink and ≥50 dB downlink gain usable; a cheap thin cable bleeds the recovered signal before it reaches the chassis, which is why the CG100 ships a specified low-loss run rather than a generic lead.

What 10 m reaches from a typical UK home

A 10 m run comfortably reaches a first-floor room from the eaves or a single-storey extension from the roof edge, and it crosses a normal loft into a home-office desk corner without splitter loss. For a bungalow it reaches the living room from the chimney stack; for a two-storey terrace it reaches the upstairs landing from the rear gable. Measure the wall-to-desk distance before unboxing, because a cable that ends 3 metres short on the loft floor cannot be stretched without a connector.

Cable upgrades: 20 m, 30 m, 40 m and 50 m

Every extra metre adds cable loss, which is why the 30 to 50 m upgrades assume a donor healthier than -105 dBm; pairing a long thin run with a -110 dBm donor starves the booster. The optional surge protector adds a fuse point at the outdoor end for exposed rural roofs and sits in series before the booster rather than replacing any connector.

Route the cable: loft, sealed window bush or drilled wall entry

Feed the coax through the loft void rather than down a rain gutter, keep bends smooth and larger than the hand-sized radius, avoid sharp kinks around a joist, and enter the building through a blanking bush in a drilled wall or a sealed window gap rather than pinching it under a closing sash. Seal the entry point with the supplied grommet or silicone to keep weather and draughts out, and leave a service loop of 30 cm at both ends so the booster can be moved without cutting the lead.

Step 4: Keep the Outdoor Omni and Indoor Whip at Least 10 m Apart

The minimum antenna separation of 10 m vertical between the outdoor donor antenna and the indoor server whip protects the amplifier from feedback. When the indoor whip radiates into the outdoor omni, the chassis hears its own output as an extra donor, raises gain, hears it again, and oscillates into a howling or unstable state; the 10 m gap plus building mass breaks that loop.

Why 10 m, and why vertical beats horizontal on a house

On a two-storey home the omni sits on the ridge and the whip stands on the ground-floor desk, giving a vertical drop of roughly 10 m through at least one ceiling and a wall; on a bungalow the omni fixes high on the gable while the whip stays in the far room. A horizontal separation across a single open floor fails because line-of-sight feedback leaks across the same ceiling height, so climb rather than slide the two antennas apart when the plan allows.

What too-close installation looks like on the LEDs

If the two antennas sit closer than 10 m, the AGC backs off hard, the band LEDs flicker or stay dim, the indoor signal jumps between strong and dead across the room, and calls break up the moment you move near the whip. Moving the whip a floor down or the omni higher on the stack clears the oscillation faster than turning gain up manually, because this unit sets gain itself.

Step 5: Connect the BS and MS Ports, and Match the Labels

The booster chassis carries two labelled sockets: BS (base station, the outdoor donor port) and MS (mobile station, the indoor server port). The outdoor omni cable lands on BS, the indoor whip lands on MS. Each connector finger-tightens; do not force a threaded SMA, and do not swap the two because the labels describe the direction of amplification.

BS: where the outdoor antenna cable plugs in

The BS port accepts the 10 m coax from the roof omni and carries the faint recovered donor into the amplifier. Route the cable to BS first, finger-tighten the adapter, and give the plug a light clockwise turn until firm; overtightening strips the SMA thread on a plastic-faced chassis.

MS: where the indoor whip plugs in

The MS port accepts the short whip lead and radiates the ≥10 dBm recovered field into the seated zone. The whip stands upright on its small base, away from a metal filing cabinet, a steel desk frame and a wall-mounted TV, which all absorb the 3 dBi spread.

Swapping the two and what it looks like

If the roof cable lands on MS and the whip on BS, the weak donor is sent to the whip as if it were output, and the amplified field feeds back toward the omni; the LEDs stay dim or flicker and the room shows no improvement. Match the labelled ports, check once more before powering on, and record the pairing on the small service sticker.

Step 6: Power-On Sequence and the 5 V DC Adapter

The CG100 runs from an AC 100–240 V 50/60 Hz to DC 5 V adapter with a UK 3-pin plug. The sequence matters: connect both antennas before applying power, because a chassis driven with only the indoor whip connected can oscillate, and the automatic gain control reads the real donor only when both ends are live.

Order: antennas first, adapter last

Step A: plug the outdoor omni cable into BS and the whip into MS. Step B: place the whip in the centre of the 100 m² seating zone on its stand. Step C: plug the 5 V DC barrel into the booster, then plug the UK adapter into the wall. Step D: switch on at the wall; never connect the adapter while the whip is close to the omni.

Automatic gain control warm-up of 3 to 5 minutes

On switch-on the AGC scans the donor, measures path loss and sets the uplink and downlink level by itself for 3 to 5 minutes; do not adjust anything during this window. It backs off when a tower looms close and recovers when the donor fades between hills, and it settles to a steady green once locked to the nearest Band 20 cell and the Band 8 voice layer.

Step 7: Read the Band LEDs After the AGC Settles

After warm-up the front-panel LEDs report the locked bands rather than the phone's subjective bars. A steady green on the Band 20 LED means the 800 MHz 4G layer is locked; a steady green on the Band 8 LED means the 900 MHz voice layer is carrying O2 or Vodafone calls; a flashing light means weak donor, searching, or the whip sitting too near the omni.

Step 8: Test Every Zone of 100 m² for 10 Simultaneous Users

The rated space of 100 m² covers a single open-plan flat, a cottage living room and kitchen, or a small home office; the 10-user count means 10 active calls and data sessions, not every registered device on the household bill. Test with real phones rather than trust the LEDs alone.

Zone map: living room, kitchen, bedroom corner, desk

Walk the room at a time: stand by the whip for the baseline, then move to the far corner of the living room, the kitchen through an internal wall, the bedroom doorway and the home-office desk. At each point run a 4G speed check, open a browser session, place a normal O2 or Vodafone voice call, and read the RSRP; the goal is a steady 4 to 5 bars and a call that does not drop after 2 minutes.

Running 10 users without a paid test lab

Gather family members or colleagues on O2, Vodafone and an MVNO such as giffgaff, Tesco or Lebara, place five simultaneous calls and open five background data sessions, then walk the far corner together. The ≥10 dBm output spreads enough field for 10 sessions in 100 m²; more than that count pushes the AGC to its limit and the far edge thins out, which is a coverage ceiling rather than a fault.

Before-and-after bar comparison

Record the bare-handset reading at the far corner before the booster runs, then repeat with the unit locked; James H. in Devon moved from 1 bar to full 5 bars in 15 minutes, Sarah M. in Yorkshire stopped O2 calls dropping entirely, and Rachel S. in a rural village got reliable 4G for the first time in three years. Those field reports describe the typical result, not a guarantee for a donor the survey never found.

10–15 Minute Installation Timeline and Tools

The basic plug-and-play setup takes 10 to 15 minutes; a wall-bracket or cable-upgrade route adds 20 to 30 minutes for drilling and sealing. The table below budgets each step for a first-time installer.

Basic tools for a basic install

No electrician is needed: a tape measure, a step ladder, a pencil, a blanking bush or silicone sealant, and a phone with field-test mode. A permanent wall bracket adds a 6 mm masonry drill, wall plug and screwdriver; the surge protector adds an in-line fuse at the outdoor end. No soldering, no crimping and no network configuration is involved, because the unit sets its own gain and locks the donor automatically.

Rural Weak-Signal Optimisation and the Second Indoor Antenna

A rural cottage often reads a weaker donor than a suburban flat, and two adjustments recover what the omni misses without changing the booster itself.

Yagi trigger: -105 to -112 dBm on one clear mast

When the survey reads -105 to -112 dBm on a single identifiable Band 20 mast and the omni cannot hold a steady green, swap to the optional high-gain directional Yagi, aim it at that tower over the hill line, and re-check the AGC. The Yagi concentrates the pickup the omni spreads around; it suits a lone mast, not a town served by several towers in different directions, where the omni's all-round pattern is the better fit.

Expandable coverage: add a second indoor antenna where the donor is strong

The product page states that coverage is expandable by adding an indoor antenna if the outside signal is strong. Where the donor reads -70 to -90 dBm, a splitter feeds a second 3 dBi whip into an adjoining room up to a total of two indoor antennas, extending the field to a second zone rather than enlarging the 100 m² ceiling. This expansion needs a healthy donor; with a faint donor the split thins both whips and helps no one.

What the CG100 Cannot Fix at Install Time

An honest guide names the ceiling before the purchase. The CG100 repeats Band 20 4G data and Band 8 voice only; it does not manufacture 3G Band 1 at 2100 MHz, does not carry any 5G band, and is rated for 100 m² rather than a whole house or a farmyard. A donor below -112 dBm on every side stays missing, a metal-clad outbuilding with no line to the mast cannot be reached by a longer cable alone, and more than 10 simultaneous sessions thin the far edge. Where those limits bite, a larger rated model rather than a louder setting is the answer; this unit sets gain itself and cannot be opened up beyond its licence-exempt class.

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