This is a one-dimensional take. All antennas receive both the electric and magnetic field. You can think of a magnetic field as being equivalent to current in a

This is a one-dimensional take. All antennas receive both the electric and magnetic field. You can think of a magnetic field as being equivalent to current in a transmission line, and the electric field being equivalent to voltage in a transmission line. Each antenna has a quantity called wave impedance that tells you what the ratio of electric and magnetic current it couples from and to (reciprocity) free air EM propagation (free air has a certain radiation resistance, and the antenna has its own radiation resistance). A dipole antenna has high-ish wave impedance, a loop antenna or magnetic antenna has a low wave impedance. It isn't the only factor to whether it is efficient or not efficient. The actual reason why transmitter antennas have to be pretty good at being efficient--receive performance is much much greater than transmit performance. Receive performance is basically limited by only the noise that comes from its various components. Transmit performance is limited, essentially, by how much power it can pull from the wall and how much power the final transmit stage can take before catching on fire. Every little bit counts for the transmit side, because increasing the power by two costs $$$$$$ whereas decreasing the receive noise floor by half isn't that big of a deal, and half the time isn't even necessary because of atmospheric noise.