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A HB9XBG Full Size Vertical Antenna for the 40m-band on Simplon Pass with view to Mount Fletschhorn. The 40-meter or 7-MHz band is an amateur radio frequency band, spanning 7.000-7.300 MHz in ITU Region 2, and 7.000-7.200 MHz in Regions 1 & 3. It is allocated to radio amateurs worldwide on a primary basis; however, only 7.000-7.200 MHz is ...
The gain and input impedance of the antenna is dependent on the length of the whip element, compared to a wavelength, but also on the size and shape of the ground plane used (if any). A quarter wave vertical antenna working against a perfectly conducting, infinite ground will have a gain of 5.19 dBi and a radiation resistance of about 36.8 ohms.
The first full scale beam waveguide antenna was the 64 meter antenna at the Usuda Deep Space Center, Japan, built in 1984 by the Japan Aerospace Exploration Agency. [6] After the Jet Propulsion Lab (JPL) tested this antenna and found it better than their conventional 64-meter antennas, [ 7 ] they too switched to this method of construction for ...
The AT&T receiving Beverage antenna (left) and radio receiver (right) at Houlton, Maine, used for transatlantic telephone calls, from a 1920s magazine. The Beverage antenna or "wave antenna" is a long-wire receiving antenna mainly used in the low frequency and medium frequency radio bands, invented by Harold H. Beverage in 1921. [1]
Traveling wave antennas Traveling wave antennas are notably one of the few types of antennas that are normally not self resonant: Electrical waves induced by received radio waves travel through the antenna wire in the direction that the arriving RF signals are travelling. Only electrical waves traveling toward the feedpoint are collected; waves ...
The J-pole antenna is an end-fed omnidirectional half-wave antenna that is matched to the feedline by a shorted quarter-wave parallel transmission line stub. [5] [1] [6] For a transmitting antenna to operate efficiently, absorbing all the power provided by its feedline, the antenna must be impedance matched to the line; it must have a resistance equal to the feedline's characteristic impedance.
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Small antennas of any kind are inefficient, but when a full-sized antenna is not practical, making a small loop with a perimeter as close to 1 / 2 wave as possible (although usually no more than 0.3 wave) makes the small loop better for transmitting, although it sacrifices or outright loses the precise "null" direction of smaller small ...