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When so loaded the antenna presents a pure resistance to the transmission line, preventing energy from being reflected. The loading coil is often placed at the base of the antenna, between it and the transmission line (base loading), but for more efficient radiation, it is sometimes inserted near the midpoint of the antenna element (center ...
This allows the antenna to be made much shorter than the normal length of a quarter-wavelength, and still be resonant, by cancelling out the capacitive reactance of the short antenna. This is called an electrically short whip. The coil is added at the base of the whip (called a base-loaded whip) or occasionally in the middle (center-loaded whip).
The HB9XBG antenna is a vertical dipole antenna for short wave radio amateurs. It was developed by the Swiss radio amateur Walter Kägi, whose call sign HB9XBG is also the designation of the antenna. [1] During the test phase in 2020, HB9XBG built two vertical dipoles – one for the 20-metre amateur radio band and another for the 40-metre band.
In this circumstance, a ‘T’-antenna is a capacitively top-loaded, electrically short, vertical monopole. [4]: 578–579 Despite its improvements over a short vertical, the typical ‘T’-antenna is still not as efficient as a full-height 1 / 4 λ [c] vertical monopole, [5] and has a higher Q and thus a narrower bandwidth.
For non directional portable use, a short vertical antenna or small loop antenna works well, with the main design challenge being that of impedance matching. With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance ; small loop antennas are tuned with parallel capacitors for ...
For monopole antennas operating at lower frequencies, below 20 MHz, the ground plane is usually the Earth; in this case the antenna is a vertical mast mounted on the ground on an insulator to isolate it electrically from the ground. One side of the feedline is connected to the mast and the other to an Earth ground at the base of the antenna. In ...