Inverse square law... inverse square law only applies in vacuum. You need to look up Friitz radar equation....basically attenuation is a function of frequency, distance, and medium. It has nothing to do with the antenna type. The type of antenna affects the directivity and efficiency, but it doesn't affect the attenuation. The size of the transmittor and receptor are also very important. The frequency has to be very high if you don't want the size to be enormous. High frequency means a lot of path loss.