Sensor node in WSNs is the major bottle neck that restricts WSNs realization due to limited processing, communication ability and power sources. The communication or wireless transmission unit has noticeable effects on wireless sensor node system, since its power consumption is dependent on the transferred data package size. This research paper presents evaluation and characterization of transmission time, minimum amount of operating voltage and current, and hence the power required to transmit certain size packets of data of an off-shelf RF ASK 315 MHz wireless module. A microcontroller with the VirtualWire library was used to provide data to the transmitter module and transmit it to the receiver, located 2 m apart, with transmitting rate of 2 kbit/s. The experimental outcome showed that the tested module would need 50 ms with 0.3 mW in order to transmit a byte of data. The transmission time increased proportionally with the data package size. Meanwhile, the transmission power increased in logarithmic manner with the data package size
