In this paper we analyzed the Radio Frequency (RF) propagation characteristics of monopole antenna in MICAz mote. During the experimental analysis, two scenarios are considered. In Scenario-I, a pair of MICAz nodes (one transmitting and one receiving node) are placed on the ground and the RSSI is measured in presence of the ground effect. In Scenario-II, only the transmitting node is placed above the ground; however, the receiving node is placed on the ground. The RSSI is measured by changing the antenna orientation at different angles and distances between them. The results show that the ground effect, antenna orientation and distance between the sensor nodes drastically affect the RSSI.