The magnetic antenna (H-Field)
original source1)
Either Ferrite Antennas or Loop Antennas
H-field antennas can be sub-divided into loop antennas and ferrite rod antennas.
Magnetic has no need to be placed high since the magnetic field is not easily attenuated. They must be minimum some meter from other electrical installations - In the garden just above the ground is ok, or attic, or balcony.
1)
Documentation System BLUE, chapter 5.2