Loading coil
（重定向自Pupinization）
![A loading coil in a small cell phone antenna on a car roof.](/Images/godic/202502/05/Small_antenna_loading_coil1258.jpg")
![Schematic of a balanced loaded telephone line. The capacitors are not discrete components but represent the distributed capacitance between the closely spaced wire conductors of the line, this is indicated by the dotted lines. The loading coils prevent the audio (voice) signal from being distorted by the line capacitance. The windings of the loading coil are wound such that the magnetic flux induced in the core is in the same direction for both windings.](/Images/godic/202502/05/Loaded_line_schematic.svg1258.png")
![(left) Toroidal 0.175 H loading coil for an AT&T long distance telephone trunkline from New York to Chicago 1922. Each of the 108 twisted pairs in the cable required a coil. The coils were enclosed in an oil-filled steel tank (right) on the telephone pole. The cable required loading coils every 6000 ft (1.83 km).](/Images/godic/202502/05/Toroidal_telephone_loading_coil1258.jpg")
![](/Images/godic/202502/05/Telephone_loading_coils_19221258.jpg")
A loading coil or load coil is an inductor that is inserted into an electronic circuit to increase its inductance. A loading coil is not a transformer as it does not provide coupling to another circuit. The term originated in the 19th century for inductors used to prevent signal distortion in long-distance telegraph transmission cables. The term is also used for inductors in radio antennas, or between the antenna and its feedline, to make an electrically short antenna resonant at its operating frequency.