OpenEnergyMonitor Community

emonTH transmit power?

Does anyone knows the transmit power for the emonTH?

As I’m unable to find it from the technical documents.

Also what is the maximum number of emonth Sensors that can be connected to a single emonPi?

Thank you to the lovely people of OEM community.

The transmit power is the JeeLib default of +7 dBm, though by modifying the code it can be turned up - but clearly at the expense of battery life, as the radio is by far the biggest consumer of power, even though it only transmits for a very short time (less than 10 ms) every minute.

Each device on the radio network must have a unique NodeID, those are limited to 30. So that’s the absolute maximum. But you must also consider that each emonTH won’t send its messages at exactly the same rate (due to timing variations) so you will get “collisions” when two messages interfere with and destroy each other. That’s unpredictable, so the real answer is, how many lost readings can you tolerate?

The currents taken from the data sheet of the RFM69CW:
+13 dBm, 45 mA
+10 dBm, 33 mA
0 dBm, 22 mA
-1 dBm, 16 mA

Sleep mode: 1 µA max.

1 Like

Hi Robert,

Thank you so much for the elaborate yet comprehensive answers. Really helps us with our work!