According to a first aspect of the present disclosed subject matter, a dynamic calibration method in a system comprising a relay, having a coil, adapted to inductively transfer power for charging a device and a transmitter, having a coil and a controller configured to inductively transmit to the relay the power for charging the device, wherein the transmitter and the relay are separated by a medium, the method comprising: determining operating parameters selected from a group consisting of minimal and maximal operating frequency; direction of power increase relative to operating frequency; minimal and maximal duty cycle; minimal and maximal operating amplitude; and any combination thereof; wherein the operating parameters and a ping frequency are determined based on dynamic measurements of the transmitter operation and calculations executed by the controller during the calibration.