Introduction: What is KNX RF?
KNX RF (Radio Frequency) is the wireless version of the KNX protocol designed for building automation in scenarios where cabling is difficult or impossible. It runs on the approved license-free frequency band (typically 868 MHz in Europe, 915 MHz in the US), and allows KNX-based switches, actuators, sensors, thermostats, and input devices to communicate over radio rather than twisted-pair bus cable.
Unlike proprietary wireless systems such as Zigbee and Z-Wave, RF maintains full interoperability across manufacturers, is configured using ETS, and works seamlessly with existing KNX TP and IP installations when combined with media couplers. RF is especially beneficial for retrofits, renovations, heritage buildings, and spaces where wiring is expensive or disruptive.
This guide explains how KNX RF works, its architecture, topology, security features, integration methods, programming process, and real-world use cases—all based on ETS methodology and KNX Association standards.
How KNX RF Works (Technical Overview)
KNX RF communication uses short radio frames defined in the KNX standard (EN 50090 / ISO/IEC 14543). The system relies on broadcast or unicast messages between devices, with mechanisms for collision avoidance and repeaters. Each RF frame includes addressing, control, and data fields similar to KNX TP telegrams but adapted for radio transmission and encryption.
Key RF Characteristics:
| Parameter | Typical Specification |
|---|---|
| Frequency | 868.3 MHz (EU), 915 MHz (US), 922 MHz (JP) |
| Modulation | FSK (Frequency Shift Keying) |
| Range | 30–100m indoor depending on walls & materials |
| Data Rate | ~16.4 kbit/s |
| Topology | Star, multi star, repeater-based |
| Commissioning | ETS with USB or RF interface |
| Security | KNX RF Secure encryption (AES-128 CCM) |
| Power | Battery or energy harvesting |
KNX RF Secure Explained
KNX RF Secure enhances the wireless KNX protocol by adding strong encryption and authentication to every telegram transmitted over radio. This prevents unauthorized access, tampering, and manipulation of building automation systems. All communication is protected using the AES-128 CCM encryption standard, ensuring confidentiality, integrity, and authenticity. The system also includes mechanisms to guard against replay attacks, telegram injection, and device impersonation. With improved key handling and secure commissioning via ETS, KNX RF Secure brings enterprise-grade cybersecurity to wireless KNX installations.
Features:
- Encrypted payload
- Sequence number / anti-replay
- Secure key provisioning
- Authentication of device identity
- ETS-based commissioning with password or FDSK
This makes KNX RF suitable for critical applications like door access, alarm signalling, hotel rooms, and residential automation where safety and privacy are mandatory.
Topology & Range
Unlike mesh-based protocols such as Zigbee, KNX RF relies on a star topology where devices communicate directly with each other or via dedicated repeaters. This simplifies system design and reduces latency, making it more predictable for professional building automation. Repeaters can be strategically placed to extend signal coverage in larger or difficult environments. However, each telegram can only be forwarded twice to prevent network congestion and looping errors. This approach ensures stable wireless communication while maintaining KNX reliability and interoperability.
RF Range Factors:
- Wall thickness & material
- Interference (WiFi, BLE, RF noise)
- Device antenna quality
- Placement / orientation
- Metal cabinets & distribution boards
➡ For large buildings you can create multi-zone coverage with multiple repeaters or hybrid RF+TP architecture.
KNX RF vs TP vs IP (Quick Comparison)
| Feature | KNX RF | KNX TP (Wired) | KNX IP |
|---|---|---|---|
| Medium | Wireless | Twisted Pair | Ethernet/WiFi |
| Speed | Low | Low | High |
| Installation | No cable | Requires bus cable | Requires network |
| Security | RF Secure | TP Secure | IP Secure |
| Range | Up to 100m | 1000m per line | LAN/WAN |
| Retrofit Friendly | ⭐⭐⭐⭐⭐ | ⭐ | ⭐⭐ |
| Programming | ETS | ETS | ETS |
➡ If you want wireless + secure + KNX interoperability → KNX RF Secure is the recommended approach.
ETS Programming
KNX RF devices are programmed using ETS just like TP devices. The only difference is the physical medium.
Requirements:
- Programming interface (USB or IP)
- Device in programming mode
- Secure key (if RF Secure)
ETS Process:
- Add RF device to ETS project
- Assign Group Addresses
- Enter RF secure key or scan QR (FDSK)
- Download application
- Test RF communication
- Save project & backup key file
Hybrid Installations (RF + TP + IP)
Most installations are not purely wireless but instead use hybrid architectures that combine RF with TP or IP. This is made possible through media couplers, which allow different communication media to seamlessly interconnect. Using a hybrid approach ensures the reliability of wired backbones while providing the flexibility of wireless where cabling is difficult. As a result, integrators can balance performance, cost, and installation simplicity in real-world projects.
Example:
- KNX TP backbone
- KNX IP backbone for visualisation / server
- KNX RF devices in rooms
- Wireless switch + RF actuator + TP line controller
Hybrid systems offer the best of both:
✔ Wired reliability
✔ Wireless flexibility
✔ KNX Secure across media
Where KNX RF is Most Useful
Renovations & retrofits
Perfect for upgrading existing buildings without damaging walls or installing new wiring. KNX RF enables modern automation in old structures using wireless controls and battery-powered devices.
Apartments & hotels
Ideal for multi-unit residential and hospitality projects where installation speed, flexibility, and minimal disruption are essential. Wireless devices allow individual room automation without running new bus cables.
Heritage buildings
Preserves architectural integrity by eliminating the need to chase walls or run conduits. KNX RF ensures full automation while respecting conservation restrictions.
Offices without false ceilings
Wireless KNX makes automation possible where cable routing is impractical. Lighting, blinds, and occupancy sensors can be added without major renovation work.
Concrete buildings
RF technology allows automation even in thick-wall constructions where wiring is difficult, using repeaters and hybrid RF+TP design to overcome range limitations.
Light partitions or glass walls
Where traditional wiring is impossible or unsafe, KNX RF provides a cable-free solution for switches, sensors, and controls on fragile or movable surfaces.
Rental properties
Perfect for rented spaces where landlords or tenants do not want permanent wiring changes. Wireless devices can be installed, removed, and reused easily.
Modular buildings
Supports prefabricated and modular construction where wireless automation reduces installation time and simplifies panelised assembly.
Temporary installations (exhibitions, shops, events)
KNX RF allows fast setup and dismantling of lighting and control systems for temporary environments, without any need for drilling or bus infrastructure.
KNX RF Device Types Available
| Category | Example Devices |
|---|---|
| Switches / Push Buttons | Gira, MDT, Jung, Zennio |
| Actuators | MDT, Theben |
| Dimmers | Elsner, Zennio |
| Sensors | Siemens, Steinel |
| HVAC Thermostats | ABB, Theben |
| RF Media Couplers | Jung, MDT |
| Remote Controls | Gira, Zennio |
| KNX RF USB / IP Interfaces | Weinzierl |
Popular Brands
- MDT Technologies
- Theben
- Gira
- Jung
- Zennio
- Elsner
- Weinzierl
- ABB
- Siemens
- Eelectron
- Steinel
KNX RF Integration With Other Systems
KNX RF can be integrated seamlessly with third-party control systems through KNX IP gateways, interfaces, and logic modules. This allows wireless KNX devices to work with platforms like Control4, Crestron, Home Assistant, and other automation servers. The RF signals are translated into standard KNX telegrams, making all functions available for visualization, scene control, and advanced automation. Integrators can also combine wireless sensors and switches with IP-based logic or cloud services for smart control. This interoperability preserves the open KNX ecosystem while enabling powerful cross-platform integration.
- Control4
- Home Assistant (via KNX IP)
- Crestron
- Savant
- RTI
- Gira G1 / Jung Smart Panel
- KNX visualisation servers (1Home, Thinka, IPAS, Babtec, etc.)
KNX RF vs Zigbee vs Z-Wave vs Thread
(Zigbee/Zwave comparison article will be separate, but include summary here for SEO)
| Feature | KNX RF | Zigbee | Z-Wave | Thread |
|---|---|---|---|---|
| Standard | ISO/IEC | IEEE | Proprietary | IP-based |
| Interop | Multi-brand | Mixed | Limited | Good |
| ETS Programming | Yes | No | No | No |
| Security | KNX Secure | Optional | Yes | Yes |
| Mesh | No | Yes | Yes | Yes |
| BMS Integration | Excellent | Poor | Poor | Medium |
| Use Case | Pro Installs | DIY/Consumer | DIY/Consumer | Smart home platform |
Cost Considerations
Cost advantages:
✔ No cabling
✔ Faster installation
✔ Lower labor cost
Cost disadvantages:
❌ RF devices usually cost more than TP
❌ Requires careful range planning
Limitations
Not ideal for high-rise or thick concrete walls without repeaters
Limited telegram throughput
Battery replacement required unless self-powered
Not mesh – range must be planned well
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Conclusion
KNX RF has matured into a reliable, secure, and professional-grade solution for wireless building automation. With KNX Secure, the technology now meets the cybersecurity needs of modern installations while maintaining backward compatibility and full ETS commissioning. From small apartments to retrofit projects and hybrid TP/IP systems, RF offers all the flexibility of wireless without giving up the interoperability and long-term stability that KNX is known for.
For installers and system integrators, KNX RF represents one of the strongest ways to deliver KNX in environments where cabling is not feasible—without switching to proprietary wireless systems.
