433.92 MHz ISM Band
433.92 MHz
Core Technical Specifications
Real-World Devices & Applications
Home Security & Automation
- Wireless alarm sensors — door/window contacts, PIR motion detectors, smoke detectors (EU market)
- Garage door openers and gate remotes (EU/UK/AU models)
- Remote-controlled mains socket switches and relay modules
- Weather station outdoor sensor units (temperature, humidity, rain gauge)
Automotive
- Car key fobs (EU-market vehicles, fixed and rolling code)
- Aftermarket central locking kits
- TPMS sensors (some EU vehicles use 433.92 MHz)
DIY & Hobbyist
- Arduino/ESP wireless links using generic TX/RX module pairs
- RC toy controllers (budget segment)
- Wireless doorbells (EU market)
Reference Circuits & Schematics
Transmitter Circuit (TX) — SYN115 / FS1000A Module
Functionally identical to the 315 MHz TX circuit, but with a 433.92 MHz SAW resonator. The SYN115 is a higher-quality alternative to the generic FS1000A, offering better frequency stability and lower spurious emissions.
| Pin | Description |
|---|---|
VCC
|
3V–12V DC supply (5V recommended for stable oscillation) |
GND
|
Ground reference |
DATA
|
OOK modulation input from MCU GPIO |
ANT
|
Antenna output — 17.3 cm wire or helical coil |
Circuit Walk-Through
The data line controls the SAW oscillator identically to the 315 MHz version. The key difference is the SAW resonator is tuned to 433.92 MHz, and the antenna must be cut to 17.3 cm (¼ wavelength at 433.92 MHz). Many EU remotes use higher-quality SAW filters for better spectral purity to meet stricter ETSI emission limits.
Receiver Circuit (RX) — SYN480R / RXB6 Module
The SYN480R superheterodyne receiver provides excellent sensitivity at 433.92 MHz. The RXB6 is the most popular budget superheterodyne module with −110 dBm sensitivity.
| Pin | Description |
|---|---|
VCC
|
5V DC (3.3V–5.5V range) |
GND
|
Ground reference |
DATA OUT
|
Demodulated digital output to MCU |
ANT
|
17.3 cm wire antenna |
Circuit Walk-Through
The superheterodyne receiver mixes the 433.92 MHz signal down to a 10.7 MHz IF using a crystal-controlled local oscillator. The IF stage provides ~60 dB gain and ±150 kHz bandwidth filtering. After IF amplification, an envelope detector and data slicer recover the digital output.
Signal Structure & Waveform Analysis
OOK Frame Structure — EV1527 Protocol (433.92 MHz)
The most common encoding for 433.92 MHz devices is the EV1527 format with 24 data bits (20 address + 4 data), identical in structure to 315 MHz EV1527 but at 433.92 MHz carrier.
Analysis & Capture Tips
- RTL-SDR at 433.920 MHz with URH or rtl_433 for automatic protocol detection
- Flipper Zero: Sub-GHz → Read at 433.92 MHz — decodes most common protocols automatically
- Use rtl_433 software to identify device type from captured signal patterns
- Check for interference from other 433 MHz devices (weather stations, doorbells) in the same area
Bench Troubleshooting & Repair Guide
1. Battery & Power Supply
MultimeterVerify coin cell > 2.8V under load. Many 433 MHz remotes use CR2025 or 27A 12V batteries — check correct type and polarity.
2. Carrier Frequency Check
RTL-SDR / Spectrum AnalyserConfirm the remote is transmitting at 433.92 MHz using an SDR or spectrum analyser. Off-frequency SAW resonators are the #1 cause of reduced range in ageing remotes.
3. Antenna Length
Ruler / NanoVNAThe ¼ wave antenna for 433.92 MHz is ~17.3 cm. Many budget modules ship with incorrectly cut antennas. Trim or extend to exactly 17.3 cm for optimal range.
4. Rolling Code Sync Loss
Manufacturer pairing procedureIf using KeeLoq rolling code (HCS301), pressing the remote >256 times out of range causes the counter to desynchronise. Re-pair the remote following the manufacturer’s procedure (usually a ‘learn’ button on the receiver).
5. PCB & Component Inspection
Magnifying Loupe / Soldering StationCheck for corroded battery contacts, cracked SAW resonator (marked ‘433M’ or ‘R433A’), cold solder joints on the oscillator, and damaged button contacts. Clean with IPA and reflow as needed.