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For radials 9 electrical degrees or less ( 1 / 40 wavelength, each, or shorter) the effect on feedpoint impedance and the current in the mast is the same as extending the height of the antenna by a length of wire equal to 99% of the total length of all the radials, up to about a dozen radials.
The antenna's feed point is at the center of the disc. It is usually fed with 50-ohm coaxial cable, with the center conductor connected to the disc, and the outer conductor to the cone. The cone: The length of the cone should be a quarter wavelength of the antenna's lowest operating frequency. [2] The cone angle is generally from 25 to 40 degrees.
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.
Vertical polarized VHF-UHF biconical antenna 170–1100 MHz with omnidirectional H-plane pattern. Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis.
When alternating current flows in a conductor it radiates an electromagnetic wave (radio wave). In multi-element antennas, the fields due to currents in one element induce currents in the other elements. Antennas are self-interacting in this respect; the waves reradiated by the elements superimpose on the original radio signal being studied.
Note that for a given antenna feedpoint impedance, an antenna's gain or increases according to the square of , so that the effective length for an antenna relative to different wave directions follows the square root of the gain in those directions. But since changing the physical size of an antenna inevitably changes the impedance (often by a ...
The vertical plane is used to plot an antenna's relative field strength perpendicular to the ground (which directly affects a station's coverage area) on a polar graph. Normally, the maximum of 1.000 or 0 dB is at the side (unless there is beam tilt ), which is labeled 0°, to 90° at the top and −90° at the bottom.
The FCC procedure to calculate HAAT is: from the proposed or actual antenna site, either 12 or 16 radials were drawn, and points at 2, 4, 6, 8, and 10 miles (16 km) radius along each radial were used. The entire radial graph could be rotated to achieve the best effect for the station.