In this paper we experimentally investigate performances of received signal strength indicator of real components for 2.4GHz RF environment, with particular attention to IEEE802.15.4 compliant transceivers (it has been adopted an MC13192 from Freescale). Results can be used to detect limits, in terms of performance, of the recently proposed algorithms based on radio signal strength indication, as localization methods or channel selection strategies to decrease power dissipation of a wireless node. Experimental results indicate a good linearity (2dB) in a limited power range [-80,- 50] dBm. Additional experiments have been also performed using a proprietary solution (formally CYWUSB6935 from Cypress), showing poorer results, in particular a non linear response. Key word -RSSI, Wireless communication, RF power measurement.