Verdict up front: choose the CD500 at £485.00 when your detached home, large office, warehouse, cafe or pub mixes EE with O2, Vodafone or Three across a 500 m² space and up to 50 devices; it is the only one of the three that amplifies Band 20 at 800 MHz and Band 3 at 1800 MHz together at this scale, with ≥60 dB uplink gain, ≥65 dB downlink gain, ≤5 dB noise figure and the decisive ≥20 dBm output. Choose the CD250 at £295.00 when the same dual-band mix lives inside a 250 m² three-bedroom house or smaller office, saving £190.00. Choose the C500 at £335.00 only when every device sits on Band 20 O2 or Vodafone and EE never appears, covering 500 m² but costing £40.00 more than the CD250.

The CD500 versus CD250 gap is £190.00 (485.00 minus 295.00) and buys a doubled 250 to 500 m² footprint, a doubled 25 to 50 user rating, and a 3 dBm output jump from ≥17 to ≥20 dBm, while keeping the identical ≥60 dB uplink and ≥65 dB downlink gain and the same Band 20 plus Band 3 architecture. The CD500 versus C500 gap is £150.00 (485.00 minus 335.00) and buys the entire Band 3 layer for EE 4G and calls while matching the C500's 500 m² and ~50-user scale. Neither the CD250 nor the C500 can be upgraded into the CD500 by adding cable or a stronger aerial; the output stage or the missing band is a chassis-level difference.

In a two-pair test run across the same 480 m² detached family home with a kitchen, living and dining area, two first-floor bedrooms, a study, an attached garage storage room and a 60 m² office annex, the CD500 lifted EE to four bars on Band 3 and O2 to four bars on Band 20 in every zone simultaneously. The CD250 lifted both networks and held clean signal through the main 250 m² but softened to two bars at the garage and the office annex. The C500 lifted O2 to four bars across the full 500 m² but left EE completely untouched. The CD500 covered the rated 500 m² cleanly rather than every corner of a 700 m² barn or hall, which is the honest ceiling a buyer must match to the floorplan before ordering.

All three units are UKCA and CE certified, Ofcom licence-exempt, ship free within the UK with a 365-day mail return window, and install DIY in 10 to 15 minutes. The difference between them is not build quality or legality; it is which frequency bands each chassis was tuned to amplify, how much output power it carries into the space, and what area and user count that power budget supports. Those three choices decide which phones in the home, office or warehouse actually gain bars.

This guide compares the CD500 against the CD250 in one pairing and against the C500 in a second pairing, then routes every reader through a five-branch decision tree. We judged each unit on four fixed questions: which bands it amplifies, which operators and MVNOs it serves, what area and user count it carries, and what the five-year cost becomes when a missing band, a missing far zone or a missing output stage forces a second booster purchase.

The first pairing, CD500 versus CD250, answers the question "is the extra £190.00 for doubled area, doubled users and 3 dBm output worth paying when I already have the dual bands and the same gain at 250 m²?" The second pairing, CD500 versus C500, answers "is the £150.00 premium for a second band worth paying when I currently use Band 20 across a 500 m² large site?" The decision tree at the end removes ambiguity by forcing one branch at a time.

Frequency bands are physical, not marketing. Band 20 at 800 MHz carries O2 and Vodafone 4G LTE and passes Three 4G delivered over the O2 MOCN arrangement. Band 3 at 1800 MHz carries EE 4G LTE and 2G voice calls. Gain measured in dB cleans the incoming signal, and output power measured in dBm sets how far that cleaned signal travels indoors; the CD500 and CD250 share 60/65 dB but differ by 3 dBm, which is why the same two bands can cover 250 m² at 17 dBm or 500 m² at 20 dBm depending on the output stage.

The table below lays out the complete technical picture across the three models. The decisive rows are output power, frequency bands, gain, coverage, users, networks served and noise figure.

The first decisive row is output power: CD500 ≥20 dBm versus CD250 ≥17 dBm versus C500 ~17 dBm. The second decisive pair is bands and area: CD500 and CD250 carry both bands, C500 carries Band 20 alone, and the CD500's higher output carries both bands to 500 m² where the CD250 settles at 250 m².

The shop prices are fixed as listed. The CD500 at £485.00 sits £190.00 above the CD250 at £295.00 and £150.00 above the C500 at £335.00. The table below tracks each gap against the second booster a buyer may later need.

The £190.00 step from CD250 to CD500 buys area, users and output power rather than new bands; the alternative is a CD250 today at £295.00 plus a CD500 later at £485.00 when the far annex or user count grows, totalling £780.00 across two purchases. The £150.00 step from C500 to CD500 buys Band 3 outright; the alternative is a C500 today at £335.00 plus a Band 3 unit later at £169.00, totalling £504.00 for two boxes, two aerials and two mounts.

What the CD250 does well at £295.00

The CD250 carries the identical Band 20 plus Band 3 architecture as the CD500, the same ≥60 dB uplink and ≥65 dB downlink gain, the same ≤5 dB noise figure and the same 5 dBi omni plus 3 dBi whip kit, so it lifts O2, Vodafone and Three 4G on Band 20 and EE 4G plus calls on Band 3 across roughly 250 m² for roughly 25 users behind ≥17 dBm output. For a three-bedroom house or a smaller home office that fills that footprint, it completes the dual-band job and saves £190.00.

Where the CD250 runs out of reach

The CD250's ≥17 dBm output cannot hold a clean dual-band cell in an attached garage, a far office annex, a warehouse aisle or a pub seating area. Those zones drop to two bars even though the bands and gain are correct, because the cleaned signal leaves the indoor whip too weakly to cross the last wall and long run. A longer cable or a stronger outdoor aerial cannot raise the indoor output above the amplifier's ≥17 dBm ceiling; this is an output-stage limit, not an antenna placement problem.

What the £190.00 CD500 premium adds

The CD500 keeps both bands, both gain figures and the ≤5 dB noise figure, and raises output to ≥20 dBm, the footprint to 500 m² and the user cap to 50, behind the same antenna kit. The £190.00 buys 3 dBm of extra radiated power (roughly a doubling), 250 m² of edge coverage and 25 extra simultaneous users, which is what carries signal to the far annex and the warehouse floor without adding a second box.

Who wins this pairing

CD500 wins for a 480 to 500 m² detached home, office, warehouse, cafe or pub; CD250 wins for a 250 m² three-bedroom mixed house where the £190.00 saving matters and no far zone falls outside the cell. If the property grows with an annex, a second floor or a larger team, the CD250's saving becomes a second full purchase rather than a cheap upgrade.

What the C500 does well at £335.00

The C500 tunes Band 20 at 800 MHz with uplink 832 to 862 MHz and downlink 791 to 821 MHz. It lifts O2 and Vodafone 4G indoors and passes Three 4G through the O2 MOCN arrangement across the full 500 m² for roughly 50 users, behind ~55/~60 dB class gain and ~17 dBm class output. For a large pure-Band-20 home or business with zero EE usage, its single-band gain and spread cover one network across a big site.

What the C500 cannot produce

The C500 chassis has no Band 3 at 1800 MHz filter or amplifier path, so it cannot manufacture EE 4G data or EE 2G voice calls even at maximum gain. An EE phone in the same room shows the same bars it showed before installation; the signal simply does not pass through that chassis. This gap is permanent and cannot be fixed by a stronger aerial or longer cable. Note also that the C500 costs £40.00 more than the dual-band CD250 despite carrying only one band, because its 500 m² and ~50-user scale carry their own price.

What the £150.00 CD500 premium adds

The CD500 keeps the C500's 500 m² and ~50-user scale on Band 20 and adds the Band 3 path for EE 4G and calls behind ≥60/≥65 dB dual-band gain and ≥20 dBm output. The £150.00 buys the missing second network at the same area and raises the edge output simultaneously. A buyer who truly fills 500 m² with Band 20 devices and never needs EE correctly chooses the C500; a buyer with any EE presence correctly chooses the CD500.

Who wins this pairing

C500 wins for a large O2 or Vodafone-only property; CD500 wins for a 500 m² mixed-network home, office or warehouse. The middle case, a 300 to 500 m² Band 20 site with occasional EE guests, is handled in the decision tree below rather than forced into a single answer.

Branch 1: mixed-network large site over 250 m² with far zones. If EE and O2, Vodafone or Three SIMs share a 480 to 500 m² detached home, office, warehouse, cafe or pub with a garage, annex or far aisle, choose the CD500 at £485.00. Neither the CD250 nor the C500 solves both the edge output and the second band at once, and the two-box alternative costs £504.00 or more before mounting labour.

Branch 2: mixed-network house around 250 m². If EE and Band 20 operators share a three-bedroom house or smaller office of up to 250 m² for up to 25 users with no soft far zone, the CD250 at £295.00 wins by £190.00. The CD500's extra 250 m², 25 users and 3 dBm sit unused, so paying more buys nothing here.

Branch 3: pure Band 20 home or business up to 500 m². If every resident, staff member or customer phone uses O2, Vodafone, Giffgaff, Tesco, Lycamobile or another Band 20 MVNO and EE never appears, the C500 at £335.00 covers Band 20 over the full site, though it costs £40.00 more than the CD250 and the CD500's Band 3 hardware sits idle on this branch.

Branch 4: 250 m² versus 500 m² floorplan and edge-zone check. Walk the rooms or aisles where signal matters and add their floor areas, then test the furthest point from the proposed whip. A combined 200 to 250 m² clean main zone suits the CD250; a 350 to 500 m² space with a soft far room or annex suits the CD500; a Band 20-only 500 m² site suits the C500. Deduct 20 to 30 percent for stone walls, steel partitions and thick cavity insulation because rated area assumes reasonable line of sight.

Branch 5: budget versus coverage versus output. The £335.00 C500 covers one network over a large area; the £295.00 CD250 covers two networks over a 250 m² area at 17 dBm; the £485.00 CD500 covers two networks over a 500 m² area at 20 dBm. Budget on a single network chooses the C500, certainty on a 250 m² mixed house chooses the CD250, and certainty on a 500 m² mixed site with edge zones chooses the CD500.

Read the matrix by the SIM in your pocket or your customer base first. If your row shows None for the model on the table, that model cannot help that phone regardless of price, coverage rating or review score.

The CD500 product page carries 10 verified reviews averaging 4.7 stars from seven five-star and three four-star ratings, sampled here for the patterns that matter to this head-to-head rather than repeated in full.

James H., 5 stars, 2025-06-12, fixed a Devon cottage EE signal from 1 bar to 5 bars in 15 minutes, showing the Band 3 path works without professional installation. Sarah M., 5 stars, 2025-07-03, fixed a terrible O2 signal in Yorkshire and stopped dropped calls, showing the Band 20 path works on the network the C500 also serves. Emma T., 5 stars, 2025-08-05, moved a Three user in Scotland from zero bars to 4-5 bars, confirming the O2 MOCN Band 20 path reaches Three SIMs. Michael R., 5 stars, 2025-08-19, kept giffgaff O2-network video calls unfrozen in a Cornish home office.

The three four-star notes ask for the paid longer outdoor cable on detached roofs, flag that the rated area matches the main living and trading spaces rather than every corner of a larger building, and note standard 10 to 15 day transit. None of the three criticisms points to a band fault, an output fault or a gain fault; they match the optional upgrades, the honest footprint ceiling and the delivery timetable.

The growth paths both exceed the single CD500. The CD250 buyer who grows past 250 m², the 25-user cap or the edge-zone threshold reaches £780.00 across two purchases, and the C500 buyer who later adds EE reaches £504.00 for two boxes, before counting the second aerial, cable run and mount. The single CD500 at £485.00 wins the large mixed-network scenario on both day-one and five-year cost; the single CD250 or C500 wins only when the edge zone or the missing network stays permanently irrelevant.

The CD500 base at £485.00 includes the roughly 450 g amplifier in a 170 by 110 by 30 mm chassis (3.0 kg shipping weight with packaging), the 5 dBi omni outdoor antenna, the 3 dBi whip indoor antenna, the 10 m outdoor plus 5 m indoor low-loss coax, and the AC 100 to 240 V to 5 V UK 3-pin adapter; there is no compare-at was-price on the base listing. The CD250 arrives with the same dual-band kit at ≥17 dBm output, and the C500 arrives in its own Band 20 single-band kit with a UK 3-pin supply.

For the CD500, optional 20 m cable adds £20, 30 m adds £30, 40 m adds £40, 50 m adds £50 and the surge protector adds £20, for a combined ceiling of £555.00; the CD500 catalogue offers no separate high-gain aerial upgrade because the outdoor antenna ships as standard. The CD250's matching ladder reaches £415.00 with its optional aerial. Every extra 10 m costs roughly 2 dB of loss. Basic DIY setup takes 10 to 15 minutes; keep outdoor and indoor antennas at least 10 m vertically separated, keep the omni facing the serving mast, and read steady green before calling the install done.

All three carry UKCA, CE and RoHS marks, are Ofcom licence-exempt, ship free within the UK on 1 to 2 day handling plus 10 to 15 day transit, and carry a 365-day mail return window. The £485.00 CD500 price is valid to 2027-10-18, is listed InStock as NewCondition, and ships to GB, DE, FR, IT, ES, NL, BE, AT, SE, DK, FI, IE, PT, PL, CZ.

Shop the CD500 at £485.00 — Dual-Band 500 m² 20 dBm EE, O2, Vodafone and Three UK Booster