ferrite antenna
Ferrite antennas belong to the group of magnetic or magnetic loop antennas, which convert the magnetic component of the electromagnetic field. They consist of a ferrite core of iron, zinc or manganese oxide on which a coil of copper wire is wound. The coil forms a tunable oscillating circuit with a parallel-connected capacitor and a variable capacitor, which is tuned to the transmission frequency with the variable capacitor. The principle of the ferrite antenna works in the long wave, medium wave and short wave range.
The ferrite antenna is tuned by the manufacturer by moving the coil on the ferrite rod and then sealing it. Reception is achieved by tuning the resonant circuit to the transmit frequency and depends on the orientation of the ferrite rod. Most electromagnetic waves are received when the ferrite rod is aligned parallel to the transmitter, i.e. at right angles to the transmitter, so that the electromagnetic waves can penetrate it optimally.
Ferrite antennas are used in radio receivers, but also in radio clocks and RFID transponders. They are suitable for frequencies up to a few megahertz. Since the received field strength depends very much on the penetration of the ferrite antenna, and this in turn on its orientation to the transmitter, receivers with built-in ferrite antennas must be rotated for optimum reception.