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Generally it consists of a quarter wave vertical radiator connected to the center of the coax feeder, and 4 radials, often sloping downwards, that are also about a quarter wave long. They are easy to build, often using a chassis-mount coax connector.
11 lut 2020 · A quarter wave monopole antenna doesn't have to have a ground plane... unless you want it to radiate EM energy with a certain efficiency and pattern. EM radiation requires accelerating electrical charges, which usually implies a voltage differential between two separated areas in space.
Example Calculations. A quarter wave (λ/4) antenna designed for 20 meter applications (15 MHz) has a length of 3.3 meters. The length of radials, assuming a 10% increase, is 3.6 meters. This assumes a velocity factor of 0.66.
My question is, 'What is so significant about 1/4 wavelength with respect to antennas.' From the information I have gathered from various sources, it is my impression that a 1/4 wavelength antenna is the most used on account of its performance.
A radiation pattern defines the variation of the power radiated by an antenna as a function of the direction away from the antenna. This power variation as a function of the arrival angle is observed in the antenna's far field.
The radiation pattern (RP) (or antenna pattern) is the representation of a radiation property of the antenna as a function of the angular coordinates. The trace of the angular variation of the received/radiated power at a constant radius from the antenna is called the power pattern.
The classic sloper antenna is a top-fed 1/4 wave vertical antenna sloping down and away from a tower. The sloper's feed point is anchored high above ground near the top of the tower on which sits a grounded HF yagi beam antenna. The yagi plays the role of a ground plane, while the tower plays the double role of reflector and grounding "rod".
