10% Duty cycle problem - Is it implemented correctly?


I’m using xbee 868 for a project.

At the moment, I transmit 8 characters every 500msec at 9600Kbps.

Each API frame has 27 bytes plus one stop bit for every byte so the transmission speed is 486Kbps.

It is 486/9600=5.3% duty cycle, so it should transmit data without problem for ever. However the XBEE stops sending data after a few minutes.

How the duty cycle is calculated?

Are you using the 868DM, or 868LP? Since you are using API mode, are you getting a TX Status response showing transmit failure?

I’m not sure duty cycle is the right wor - you seem to be estimating load or bandwidth utilization.

If you are using the older high-power 868LP, that one has problems if your nodes are too close together - I was told they had to be at least 5-6 meters apart or the RX circuits over-saturate.


I am using the long-range modules.

I have set the transmission power at the lowest level and the modules are more than 5 meters away.

Do the module transmit zeroes between packet transmissions? If not, the bandwidth utilization is the duty cycle.

10% duty cycle limit means that every hour it can transmit for 6 minutes.

With 9600Kbps transmission speed, you can transmit 6609600/8/1024=421.875KB/hour.