For calculating free space path loss without accounting for antenna gain enter “0” in both Transmitter and Receiver Gain fields. For calculating path loss including the gain provided by antenna systems enter the gain values for each antenna.  For example; to determine the total path loss between 6dB gain antenna at a public safety radio site and a building with a 10dB gain yagi antenna, enter 6 and 10 in their respective fields.  Since RF path losses are bi-directional it does not matter which value is entered in which field, the path loss results will be the same.