In an aspect, the disclosed technology relates to embodiments of a lossy ferrite-core and dielectric-shell (LFC-DS) structure in an axial-mode helical antenna (AM-HA) or a meandered dipole antennas. The instant topology can be used to facilitates the broader use of ferrite materials, including lossy ferrite material, for a miniature AM-HA or meandered dipole antennas, e.g., by overcoming the lossy characteristics of the lossy ferrite. The resulting miniature AM-HA can be used for high frequency operation, including at over 1 GHz, making the instant topology suitable for very high frequency (VHF) and ultra-high Frequency (UHF) applications.

In an aspect, the disclosed technology relates to embodiments of a lossy ferrite-core and dielectric-shell (LFC-DS) structure in an axial-mode helical antenna (AM-HA) or a meandered dipole antennas. The instant topology can be used to facilitates the broader use of ferrite materials, including lossy ferrite material, for a miniature AM-HA or meandered dipole antennas, e.g., by overcoming the lossy characteristics of the lossy ferrite. The resulting miniature AM-HA can be used for high frequency operation, including at over 1 GHz, making the instant topology suitable for very high frequency (VHF) and ultra-high Frequency (UHF) applications.

An underground transmitter can be configured for use with a drill head and configured for wireless communication. The underground transmitter can include a control circuitry and a multi-coil antenna assembly. The control circuitry is configured for transmitting data associated with an operation of the drill head. The multi-core antenna can include an antenna core and a plurality of distinct wire coils. The plurality of distinct wire coils can be positioned proximate (e.g., around) the antenna core, with the distinct wire coils each having a different inductance associated therewith and thereby capable of transmitting in a separate frequency range. The control circuitry can be selectably coupled with the distinct wire coils to control which of the distinct wire coils are activated and thereby generating data signals at a given time.

An eLORAN receiver may include an antenna and eLORAN receiver circuitry coupled to the antenna. The antenna may include a ferromagnetic core and an H-field signal winding coupled to the ferromagnetic core. The eLORAN receiver may have an antenna tuning device including a tuning winding surrounding the ferromagnetic core, and a tuning circuit coupled to the tuning winding.

An eLORAN receiver may include an antenna and eLORAN receiver circuitry coupled to the antenna. The antenna may include a ferromagnetic core and an H-field signal winding coupled to the ferromagnetic core. The eLORAN receiver may have an antenna tuning device including a tuning winding surrounding the ferromagnetic core, and a tuning circuit coupled to the tuning winding.

A coil device has a plate-like element body having a main surface, a back surface, and an end surface, a helical coil provided in the element body and having a coil axis extending between the main surface and the back surface, and a connection terminal provided on the back surface or the end surface of the element body and connected to the helical coil. As for a conductor constituting the helical coil, a plurality of conductor portions extending along the main surface are comprised of a plurality of metal pins, respectively.

A coil device has a plate-like element body having a main surface, a back surface, and an end surface, a helical coil provided in the element body and having a coil axis extending between the main surface and the back surface, and a connection terminal provided on the back surface or the end surface of the element body and connected to the helical coil. As for a conductor constituting the helical coil, a plurality of conductor portions extending along the main surface are comprised of a plurality of metal pins, respectively.

A coil device includes a core member, a bobbin, a coil portion, an outer case, and a potting resin. The core member extends in a longitudinal direction. The bobbin is provided with a longitudinal concave portion communicating with a side surface opening portion open to outside and housing the core member. The coil portion is provided with a wire wound around the bobbin. The outer case is provided with a housing concave portion configured to house the bobbin housing the core member and have the coil portion. The potting resin is filled in the housing concave portion and surrounds the bobbin with the coil portion. An opening port of the housing concave portion and the side surface opening portion are open in the same direction.

A rod-shaped magnetic core element, having a first end with a spherical or cylindrical recess or a spherical or cylindrical connecting protrusion, and a second end with a spherical or cylindrical recess or a spherical or cylindrical connecting protrusion so that a bent connection of at least two magnetic core elements is variably adjustable. Magnetic core elements comprising spherical or cylindrical magnetic core ends of this type allow a nearly gap-free construction with little magnetic leakage due to slightly larger end surfaces in comparison with ferrite rods having beveled plane end section surfaces. The enlarged end surface of the spherical surface advantageously allows a more stable connection of individual magnetic core elements without adhesive bonding. This allows the construction of flexible, multiple-member and inexpensive rod core coils and antennae.

A rod-shaped magnetic core element, having a first end with a spherical or cylindrical recess or a spherical or cylindrical connecting protrusion, and a second end with a spherical or cylindrical recess or a spherical or cylindrical connecting protrusion so that a bent connection of at least two magnetic core elements is variably adjustable. Magnetic core elements comprising spherical or cylindrical magnetic core ends of this type allow a nearly gap-free construction with little magnetic leakage due to slightly larger end surfaces in comparison with ferrite rods having beveled plane end section surfaces. The enlarged end surface of the spherical surface advantageously allows a more stable connection of individual magnetic core elements without adhesive bonding. This allows the construction of flexible, multiple-member and inexpensive rod core coils and antennae.