Why exam signal jammers matter more than ever in 2026
Exam cheating used to require an accomplice outside the building and a receiver that could only manage a voice call. In 2026 the hardware is smaller, cheaper and far more capable: a 5G module the size of a coin, a bone-conduction earpiece that is invisible under an ear canal check, and a phone in a bag outside the room acting as the relay. The economics have shifted, and so has the band plan needed to stop it.
Scale explains the pressure. China's national college entrance examination recorded 13.42 million candidates in 2024 and 13.35 million in 2025, and the 2026 figure published by the Ministry of Education is 12.90 million. India shows the same pattern from a different angle: the 2024 NEET-UG medical entrance exam, taken by roughly 2.4 million candidates, was engulfed by a paper-leak scandal that led to a re-test for 1,563 candidates and a national review of examination security.
What changed technically is the fallback ladder. A modern handset in an exam room will try 5G, then LTE, then 3G, then 2G, then WiFi if the venue offers a guest network, and a cheating earpiece may sit on 2.4 GHz Bluetooth rather than on any cellular band at all. Blocking one rung does not block the ladder. That is the design problem this guide addresses: not “how many watts”, but which bands, how much power where, and how you will prove the result on the day.
Frequency bands you must cover
Jammers work on the uplink as well as the downlink, but for exam venues the uplink is what matters: deny the handset ability to reach the base station and nothing leaves the room. The table below lists the bands that appear in real procurement specifications, in the order they usually appear in a quotation.
| Band | Uplink range | What it carries | Why it matters in an exam room |
|---|---|---|---|
| GSM 900 | 880-915 MHz | 2G voice and SMS | Still the fallback layer in many rural and cross-border sites |
| GSM 1800 | 1710-1785 MHz | 2G voice and SMS | Shares spectrum with LTE 1800, so one band covers two generations |
| WCDMA 2100 | 1920-1980 MHz | 3G voice and data | Legacy but still deployed where 4G coverage is thin |
| LTE 1800 / 2600 | 1710-1785 / 2500-2570 MHz | 4G data and VoLTE | VoLTE matters: a blocked data path does not stop a voice call |
| 5G n78 (3500) | 3300-3800 MHz | 5G data, NSA and SA | The band most often missing from older jammer stock |
| 5G 4900 | 4800-4900 MHz | 5G capacity layer in China | Deployed widely in mainland venues; check locally before specifying |
| WiFi 2.4 / Bluetooth | 2400-2483.5 MHz | Local data, earpieces, cameras | Bone-conduction cheating earpieces often run on 2.4 GHz |
| WiFi 5.8 | 5725-5850 MHz | Video and high-rate data | Also carries drone video, so the same band serves counter-UAS work |
Country differences are not cosmetic. Europe leans on 800, 900, 1800, 2100 and 2600 MHz with 5G at 3400 to 3800 MHz. North America adds 600, 700 and AWS blocks, which is why a band set built for China will leave gaps in a US venue. India uses 1800, 2100, 2500 and 3500 MHz with wide variation between circles. The Gulf states generally mirror European allocations but apply their own type approval.
Partial coverage fails predictably. A device blocked on 5G falls back to LTE, then to 2G voice, and may still reach a cheating earpiece over 2.4 GHz Bluetooth; multi-SIM handsets double the paths. That is why reputable specifications list every band with its uplink range, and why a quotation claiming “full band” without a table is incomplete.
Power calculation by room size
Power selection is a link-budget problem, not a floor-area table. The handset is listening to a base station, so the jammer must arrive at the handset louder than that signal by a margin sufficient to prevent registration. The working formula is:
- P_tx — jammer output per band at the antenna port, dBm
- S_rx — signal level the handset receives from the cell, typically -75 to -95 dBm indoors
- J/S — jammer-to-signal margin, 6 to 10 dB in practice
- L(d) — path loss from antenna to the furthest seat: free-space loss 32.4 + 20log10(f MHz) + 20log10(d km), plus wall attenuation
- G_ant — antenna gain in dBi, typically 3 to 8 dBi for indoor directional panels
Wall attenuation is where most estimates go wrong: drywall costs about 3 dB, brick 10 dB, concrete 15 dB, reinforced concrete 20 to 25 dB. A room that looks like 60 square metres can behave like 150 if the antenna is separated from the back row by two structural walls.
| Room size | Construction | Base station distance | Recommended output | Layout |
|---|---|---|---|---|
| 50-80 m2 | Drywall or plaster partition | Cell site over 500 m away | 10 W, one unit | Centre ceiling, one omnidirectional antenna |
| 50-80 m2 | Brick or concrete | Cell site 200-500 m away | 10-20 W | Centre or front wall, directional antenna facing seats |
| 100-200 m2 | Standard classroom partitions | Outdoor macro cell in sight | 20-30 W | Two units, or one unit with two antennas |
| 100-200 m2 | Reinforced concrete shell | Cell site within 200 m | 30-50 W | Two units at opposite ends, directional, angled away from windows |
| 300 m2 and above | Mixed, exam hall or gymnasium | Any | 50 W or 3-4 units at 10-20 W | Distributed units along the ceiling grid, output reduced per unit |
| Any size, near a base station | Any | Cell site on the roof or across the street | Add 6 dB to the row above | Directional antennas, verify leakage at boundary before acceptance |
Read the table as a starting point to verify on site, not as a specification. The numbers that decide the final setting are the ambient downlink level at the worst seat and the permitted emission at the boundary; a site survey measuring both is worth more than any calculator.
Installation best practices
Height, position and antenna choice decide more of the outcome than another 10 W. Mount the antenna between 2.5 and 3.5 metres above the floor, below the ceiling plane if the ceiling is metal, and roughly over the centre of the seating area. A directional panel aimed along the rows covers more evenly than an omnidirectional antenna mounted in a corner, where output follows the adjacent walls and leaves the far row short.
For halls of 300 square metres and above, distribute rather than concentrate: three or four units at 10 to 20 W along the ceiling grid, each covering a zone, give a flatter level across the room and far less leakage outside. Keep cable runs short and use low-loss coax; a 10-metre run of thin cable can cost 3 dB, which is half the power you paid for.
Leakage control belongs in the design, not in the aftermath. Point directional antennas inward and away from windows, keep units away from exterior walls facing public space, and prefer several low-power units over one high-power transmitter. In multi-room buildings, synchronise or stagger units so coverage is continuous across the corridor without raising output per room. Finally, measure at the boundary before acceptance: the corridor, the adjacent classroom and the nearest public footpath are the three places a complaint will come from.
Compliance and legal considerations
Radio jamming is restricted nearly everywhere, and product certification does not confer a right to transmit. In China, jamming equipment is regulated under radio management rules and may be used only by authorised bodies for designated purposes, typically examinations, prisons and designated security sites, with approval from the competent authority. In the United States, the FCC prohibits jamming by private parties and state and local authorities, with narrow federal exceptions. European countries generally require a national authorisation, and the United Kingdom treats jamming as an offence under wireless telegraphy legislation.
For equipment, the relevant certificates are CE (EMC directive and the Radio Equipment Directive) with a declaration of conformity, RoHS for materials, and local type approval where the destination market requires it, such as WPC approval in India or telecom authority registration in the Gulf. Ask what the declaration covers: a model list, the bands tested, the standards applied and the laboratory that issued the reports. A supplier who cannot produce the model list behind a CE mark is offering a logo, not a certificate.
Legitimate deployment scenarios share one feature: an authority with a legal basis, such as an examination board authorisation, a correctional facility, a military site or a government venue hosting a protected event. Private venues and schools without authorisation are not in that list, which is why the purchasing question is not only which jammer, but which approval the venue already holds.
Acceptance testing checklist
Acceptance is a measurement exercise with a signature at the end. Use a spectrum analyser with a calibrated antenna if the budget allows, or a handset in field test mode if not, but record numbers rather than impressions. A school hall takes an afternoon.
- 01Divide the room into a grid of at least five points: four corners and the centre. Large halls need one point per 50 square metres.
- 02Record the ambient downlink level at each point before switching anything on, using a phone in field test mode or a spectrum analyser with a calibrated antenna.
- 03Switch on the jammer with the full band set and repeat the measurement. The downlink level should fall below the level at which the handset can register.
- 04Attempt a call, an SMS and a data session at each point, on each mobile network present in the room, not just the operator you happen to use.
- 05Walk the boundary: corridor, adjacent rooms, entrances and any window facing a public street. Confirm the emission outside the controlled area stays within the authorised limit.
- 06Repeat the whole sequence with a second handset generation if the venue hosts mixed devices, because a 5G handset can fall back to LTE or 2G and still connect.
Hand over a document set with the installation, not after it. The list below is what auditors, insurers and the venue's own compliance team tend to ask for.
- Band-by-band measurement table with point, time, operator and measured level
- Site plan showing unit positions, antenna orientation and cable routes
- Serial number list of every installed unit and antenna
- CE declaration of conformity and RoHS statement for the supplied models
- Copy of the operating authorisation issued to the venue
- Operator briefing record and a one-page fault response procedure
Common mistakes to avoid
These four failures account for most disappointing installations we are asked to diagnose. None is a hardware fault, and all are avoidable at specification stage.
Buying power by habit instead of by room
A 50 W unit in a 60 square metre room leaks into the corridor and the street, creates complaints, and often performs no better inside than a 10 W unit placed correctly. Underpowering fails the other way: the handset keeps a usable link at the back row, and nobody notices until a device is found.
Specifying only 2G and WiFi
Cheating hardware moved to 4G and 5G years ago, and a handset that loses 5G falls back to LTE, then to 2G, then to WiFi if the venue offers it. A band plan that stops at 2.4 GHz blocks the least capable devices and none of the capable ones.
Mounting above a metal ceiling or behind a column
Suspended metal ceilings and structural columns shadow the signal. The room looks covered on the plan and has dead spots in reality. Antennas belong below the ceiling plane and in the open, even if that means a visible cable run.
Skipping acceptance testing
Without a measured record there is no way to prove the system worked on the day, distinguish a design fault from a failed module later, or defend the installation if a complaint arrives. The test takes an afternoon; the argument without it takes months.
A short pre-purchase checklist
- Room areaMeasure the floor, not the seat count. A 60 square metre room with 40 seats and a 60 square metre room with 20 seats need the same coverage.
- ConstructionCount walls between the antenna and the furthest seat. Reinforced concrete gains 20 to 25 dB, brick about 10 dB, drywall 3 dB.
Frequently asked questions
How much power does a typical exam room need?+
A 50 to 80 square metre room with standard partitions usually needs 10 W from one correctly placed unit. Concrete walls or a nearby base station push that to 20 W. A 100 to 200 square metre room needs 20 to 30 W, and halls above 300 square metres are better served by three or four distributed 10 to 20 W units than by one large transmitter.
Which bands are essential in 2026?+
At minimum 2G 900 and 1800, 3G 2100, LTE 1800 and 2600, 5G n78 at 3500 MHz, and 2.4 GHz WiFi and Bluetooth. Add 5G 4900 where it is deployed and 5.8 GHz WiFi if the venue has that network. Anything less leaves a fallback path open.
Can a jammer block 5G without blocking 4G?+
It can, but that is usually the wrong goal. A 5G handset that loses its 5G carrier will attempt LTE, and most networks are still anchored on LTE. Effective coverage blocks the whole ladder of generations the handset can reach, which is why band sets are specified together rather than one band at a time.
Will the jammer affect neighbouring classrooms or homes?+
It will if the output is oversized or the antenna points at a window. Control comes from three things: the lowest power that passes acceptance, directional antennas aimed inside, and a boundary measurement at the wall, corridor and street. If the boundary test fails, reduce power before adding units.
Is a jammer legal to buy and operate?+
In most countries jamming is prohibited for private parties and permitted only for specific authorities under authorisation. China, for example, restricts use to designated venues with approval. Buyers must confirm their own legal basis; equipment certification such as CE covers product compliance, not the right to transmit.
What certifications should the equipment carry?+
For European-bound projects, a CE declaration covering EMC and the Radio Equipment Directive, plus RoHS. For other markets, local type approval or import permits may apply. Ask for the declaration, the test reports behind it and the model list it covers, since a declaration for one model does not cover a different band set.
How do I verify the system actually works?+
Measure the downlink level at five or more points with the system off and on, then attempt calls, SMS and data on every operator present. A handset that cannot register and cannot complete a data session is the evidence. Record band, point, time and measured level in a table signed by the venue.
Why does the equipment get hot, and is that a problem?+
Amplifiers convert part of the DC input into heat, so a warm heatsink is normal. The test is whether output power holds: if forward power drops by more than about 0.5 dB over thirty minutes, or the case temperature keeps climbing instead of levelling, the thermal path or airflow is inadequate for the enclosure.
Can one unit cover a whole exam building?+
Rarely, and not lawfully in most jurisdictions: power needed to pass several concrete slabs would exceed the permitted boundary emission. Distributed low-power units per room or floor cover better inside with less leakage outside, and one failed unit does not take the site offline.
What should a quotation include?+
Band plan with uplink ranges, output per band, antenna gain, coverage claim with its assumptions, power supply and mounting hardware, spare modules, test documentation, and delivery and warranty terms. A quotation listing only total watts cannot be compared with another.
Conclusion
A working exam signal jammer installation is decided by three documents: a band plan that matches the handsets actually present, a power and placement calculation based on the room rather than the catalogue, and an acceptance record that proves the result. Equipment comes fourth. Buyers who get the first three right usually find that a modest, well-placed system outperforms an oversized one, and that the venue's legal position is easier to defend because the authorisation and the measurement sit in the same folder.
We build jammers in Shenzhen and have supplied band sets for exam venues, prisons and conference facilities since 2013. For a project under specification, send the room dimensions, wall construction, operators present and the bands you believe you need; you will get a band plan, an output recommendation and the assumptions behind it.