After ww II, fermites became popular as a magnetic core usable well into the radio spectrum. The earlier air core loops were replaced by compact ferrite core antennas called loopsticks. These could use less wire for the same inductance and fit better in the more compact radios of the period. Such antennas were also used in marine-radio direction finders, used to determine the bearings to MF beacons that were located throughout bays and harbors. These were used until the advent of more recent LORAN C and then GPS navigation systems. As I will discuss in the next chapter, receiving loops can be used to advantage as directional antennas for reception in the MF and low HF bands, discriminating against noise and interference by taking advantage of their directional properties.