From the work of Heaviside ( 1887 ) it had become clear that the performance of telegraph lines, and most especially telephone lines, could be improved by the addition of inductance to the line . lumped components such as the loading coils.
42.
The equivalent circuit of the antenna ( including loading coil ) is the series combination of the capacitive reactance of the antenna, the inductive reactance of the loading coil, and the radiation resistance and the other resistances of the antenna-ground circuit.
43.
The equivalent circuit of the antenna ( including loading coil ) is the series combination of the capacitive reactance of the antenna, the inductive reactance of the loading coil, and the radiation resistance and the other resistances of the antenna-ground circuit.
44.
To keep a balanced point of view, it is important to note that a vertical or dipole antenna that is short compared to a wavelength, matched using a small loading coil " also " has a high voltage present at the loading coil.
45.
To keep a balanced point of view, it is important to note that a vertical or dipole antenna that is short compared to a wavelength, matched using a small loading coil " also " has a high voltage present at the loading coil.
46.
Campbell was aware of Heaviside's work in discovering the Heaviside condition, in which the specification for distortionless transmission of signals is formulated, but apparently was not aware of Heaviside's suggestion of using loading coils to force a line to meet it.
47.
The loading coil is usually inserted at the base of the antenna, between it and the transmission line ( " base loading " ), but sometimes it is inserted in the center of the antenna element itself ( " center loading " ).
48.
However the paper was blocked by Arthur's superior, William Henry Preece of the Post Office, because part of the proposal was that loading coils ( inductors ) should be added to telephone and telegraph lines to increase their self-induction and correct the distortion which they suffered.
49.
It can be seen that at low frequencies the design of the loading coil can be challenging : it must have high inductance but very low losses at the transmitting frequency ( high Q ), must carry high currents, withstand high voltages at its ungrounded end, and be adjustable.
50.
Loading coils inserted periodically in series with a pair of wires reduce the attenuation at the higher voice frequencies up to the cutoff frequency of the low-pass filter formed by the inductance of the coils ( plus the distributed inductance of the wires ) and the distributed capacitance between the wires.
