EN 300 328 — Harmonised Standard for 2.4 GHz Radio Devices
ETSI EN 300 328 (Wideband transmission systems; Data transmission equipment operating in the 2,4 GHz band) is the foundational harmonised standard governing radio frequency (RF) and electromagnetic requirements for virtually every wireless product that operates in the 2.4 GHz ISM band. If your product includes Wi-Fi 2.4 GHz, Bluetooth Classic, Bluetooth Low Energy (BLE), Zigbee, Thread, or any other 2.4 GHz wireless technology — EN 300 328 is the primary standard that determines whether you can self-declare CE marking compliance under the Radio Equipment Directive.
Key Facts
| Detail | Information |
|---|---|
| Full title | ETSI EN 300 328 V2.2.2 — Wideband transmission systems; Data transmission equipment operating in the 2,4 GHz band; Harmonised Standard for access to radio spectrum |
| Developed by | ETSI (European Telecommunications Standards Institute) |
| Current version | V2.2.2 (2019-07) |
| Standard type | Harmonised European Standard (hEN) |
| Published in OJEU | Yes — provides presumption of conformity with RED Article 3(2) |
| Applicable directive | Radio Equipment Directive (RED, 2014/53/EU) |
| Frequency range | 2,400–2,483.5 MHz (2.4 GHz ISM band) |
| Technologies covered | Wi-Fi 802.11b/g/n/ax (2.4 GHz), Bluetooth Classic and Bluetooth LE (all Core Specification versions), Zigbee, Thread, proprietary FSK/GFSK/DSSS/OFDM systems |
What EN 300 328 Tests
EN 300 328 verifies compliance with RED Article 3(2) — the requirement that radio equipment uses the radio spectrum efficiently and does not cause harmful interference to other spectrum users. The standard defines:
1. Maximum Transmit Power (EIRP)
The maximum allowed equivalent isotropically radiated power in the 2.4 GHz band:
- General limit: 100 mW EIRP (20 dBm)
- No higher power is permitted; equipment transmitting at 10 dBm EIRP or more must either be adaptive or, if non-adaptive, keep its Medium Utilisation factor at or below 10%
The test measures transmitter output power at the antenna port and, where applicable, at a reference antenna to calculate EIRP.
2. Power Spectral Density
For non-frequency-hopping equipment (DSSS, OFDM and other wideband modulations), the standard limits power spectral density to 10 dBm per MHz EIRP, so that no narrow part of the signal carries a disproportionate share of the power. The limit does not apply to frequency-hopping (FHSS) equipment.
3. Occupied Bandwidth
For frequency hopping systems (Bluetooth uses FHSS), the occupied bandwidth of each hopping channel must be within defined limits. For DSSS systems like Wi-Fi, the channel bandwidth must conform to the defined spectral mask.
4. Duty Cycle (for non-adaptive equipment)
Equipment that does not implement an adaptive mechanism and transmits at 10 dBm EIRP or more must keep its Medium Utilisation factor — (output power ÷ 100 mW) × duty cycle — at or below 10%, stay within its declared duty cycle, and respect transmit-sequence and gap limits (for non-hopping equipment: sequences of at most 10 ms, gaps of at least 3.5 ms).
5. Adaptability (Listen-Before-Talk / Detect-and-Avoid)
Since V1.8.1 (2012), EN 300 328 has contained adaptivity requirements: equipment transmitting at 10 dBm EIRP or more must be adaptive or stay within the non-adaptive limits above. Adaptive non-hopping equipment uses Detect and Avoid (DAA) or listen-before-talk as Load-Based Equipment (LBE) or Frame-Based Equipment (FBE):
- LBE (Load-Based Equipment): Implements listen-before-talk (LBT) — senses the channel before transmitting and backs off when the channel is occupied.
- FBE (Frame-Based Equipment): Uses a fixed-period frame structure with defined listen periods between transmit bursts.
Wi-Fi (802.11) with CSMA/CA inherently implements LBE. Bluetooth with its adaptive frequency hopping (AFH) implements a form of detect-and-avoid. Proprietary protocols must implement one of these adaptive mechanisms (DAA or LBT) to transmit at 10 dBm EIRP or more without the 10% Medium Utilisation limit.
6. Frequency Range and Channel Plan
The standard defines which channels are permitted within 2,400–2,483.5 MHz and tests that the transmitter operates only on permitted channels.
7. Spurious Emissions
Out-of-band and spurious emissions — radio energy radiated outside the intended channel — must be within the limits defined in EN 300 328 itself; ETSI EN 301 489 is the separate EMC standard covering RED Article 3(1)(b).
EN 300 328 and Other 2.4 GHz Standards
EN 300 328 addresses radio spectrum (RED Article 3(2)) but not all RED essential requirements. A complete 2.4 GHz radio product typically requires:
| Standard | What It Covers | RED Article |
|---|---|---|
| EN 300 328 | RF spectrum efficiency, transmit power, duty cycle, LBT | Art. 3(2) — Spectrum |
| ETSI EN 301 489-1 + -17 | Electromagnetic compatibility (EMC) — conducted and radiated immunity and emissions | Art. 3(1)(b) — EMC |
| IEC 62368-1 / EN 62368-1 | Electrical safety — protection from electric shock, fire, energy hazards | Art. 3(1)(a) — Safety |
| EN 18031-1 | Cybersecurity baseline (for RED Delegated Act products) | Art. 3(3)(d) |
| EN 62311 | RF exposure / SAR — for devices used close to the body | Art. 3(1)(a) |
A CE Declaration of Conformity for a typical Wi-Fi or Bluetooth product must cite all applicable standards from all these categories.
Version History and Key Changes
| Version | Date | Key Change |
|---|---|---|
| V1.7.1 | 2006 | Earlier version, widely referenced |
| V1.8.1 | 2012 | Major revision — introduced adaptivity (LBT/DAA, LBE/FBE) and the Medium Utilisation factor |
| V1.9.1 | 2015 | Transitional version |
| V2.1.1 | 2016 | First version under RED (2014/53/EU) — added receiver blocking |
| V2.2.2 | 2019 | Current version — revised receiver blocking, clarified terminology |
Important: Only EN 300 328 V2.2.2 is cited in the Official Journal; the reference to V2.1.1 was withdrawn on 6 August 2021. Test reports to earlier versions no longer support a presumption of conformity under RED, so such products need re-testing to V2.2.2 or assessment with a notified body.
Antenna Considerations
EN 300 328 tests are antenna-dependent. For products with:
- Integrated antennas — Testing is performed with the product as shipped; no separate antenna port measurement needed in many cases.
- Detachable antennas (with fixed type) — Testing with the antenna supplied; antenna type must be specified in the technical file.
- Detachable antennas (user-configurable) — All permitted combination of antenna types must be tested or bounded by analysis; maximum EIRP with highest-gain permitted antenna must not exceed limits.
Module manufacturers (selling certified radio modules to product integrators) must define the maximum antenna gain their certification covers. Product integrators using the module must not connect antennas exceeding this gain.
Pre-compliance Testing
For hardware development teams, pre-compliance testing against EN 300 328 can identify issues before formal accredited lab testing:
- Spectrum analyser measurement of transmit power and occupied bandwidth
- Peak power and duty cycle measurement using an RF power meter
- LBT verification using a programmable signal generator to inject an occupied-channel signal and verify the DUT backs off
These pre-compliance checks do not replace accredited laboratory testing for CE marking but can catch obvious non-conformities early in the development cycle.
Related Terms
- EN 301 893 — The companion standard for 5 GHz Wi-Fi (RLAN) devices.
- RED — The directive under which EN 300 328 provides presumption of conformity.
- RED Delegated Act — Cybersecurity requirements layered on top of RED; applies to internet-connected 2.4 GHz devices.
- ETSI — The standards body that develops and maintains EN 300 328.
- CE Marking — The market access mark that EN 300 328 compliance supports.
- EN 18031 — The cybersecurity harmonised standard that applies alongside EN 300 328 for RED Delegated Act products.
Inovasense designs hardware products for the 2.4 GHz ISM band — Wi-Fi, BLE, Zigbee, and multi-radio platforms — with EN 300 328 compliance built into the RF design phase. We coordinate accredited laboratory testing and compile the complete technical file for CE marking under RED. See our embedded wireless hardware and EU compliance services.
Official References
- EN 300 328 — ETSI standard for 2.4 GHz wideband modulation — ETSI (2.4 GHz ISM band standard)