Low electromagnetic radiation detection for XBee-PRO ZB S2B

Hi all,

I’ve been testing some XBee-PRO ZB S2B devices with a electromagnetic radiation detector. As result, I’ve found some unexpected values I hope you could help me to understand:

The nodes in the network are configured to use maximum RF power (PL register set to 4, and PM register set to 1). In consequence, the power at devices’ amplifier output should be 12 dBm.

Additionally, the tests was performed using a standard pigtail (10mm long, UFL to SMA), and a standard antenna (Quad Band [824-960/1710-1900], 3dBi, and SMA Connector). Both elements were provided by our national DIGI distributor, to be used with XBee devices.

Once all devices are deployed forming a network and interchanging information, an electromagnetic radiation detection equipment was used to measure the power next to each one of DIGI devices’ antennas. The maximum radiation peak detected by the equipment in 2.4 GHz band was -40dBm.

Is there any reason to obtain these low power measurements? Shouldn’t we be detecting at least 10dBm?

José M.

Additionally, the maximum wireless range measured between 2 XBee devices was 40-50m indoor, so it seems to be working OK.

You are comparing two different values at this moment. The number that you can obtain from the datasheet of 12dBm are conducted measurements, while the measurement you are describing is a radiated one. You will never obtain a match. Also, consider that we do not know the internals from the driver for which the maximum output power setting that you refer to could be a max. limit and not a fix setting to transmit at max. output power.

With all this, what I mean is that the test that you are describing, if radiated, cannot be used to compare the datasheet figures unless you know the radiation pattern of the antennas and estimate the losses between your emitter and your receiver, considering that you can control the rest of you environment like reflections and there are not other devices transmitting that could affect your readings.