Web Multiband Simulator
Reproduce radio time signals to sync radio-controlled watches.
Please star the project on GitHub if you find it helpful!
Global Signal Coverage
Radio-controlled clocks automatically synchronize to one of these regional longwave transmitters. Select the one that suits your watch's supported frequencies and your location/timezone for the best results.
68.5 kHz
60 kHz
77.5 kHz
60 kHz
40 & 60 kHz
How to Use
Sync your computer's time with an accurate time source (e.g., time.is, or a NTP server such as pool.ntp.org) to ensure the simulator transmits the correct time signals.
Use a headphone or the computer's built-in speaker. Maximize the volume for better reception, and place your radio-controlled clock close to the speaker.
Press Start Transmitting, set your clock to its manual sync/receive mode, and wait. Because these protocols transmit one frame per minute, it usually takes several minutes for a clock to successfully decode the time.
Important Notes
Disclaimer: This simulator is provided "as is" for educational and experimental purposes. The author assumes no responsibility for any damages, missed alarms, or late appointments resulting from the use of this tool.
This project is only tested limitedly. Feedback and contributions are very welcome to improve the simulator's accuracy and usability.
This project is heavily inspired by the open-source web-jjy project.
© 2026 Chuanjin Su. Released under the MIT License.