A vertical antenna radiates electromagnetic waves primarily due to the oscillating electric current that flows up and down its length. This oscillating current generates an electromagnetic field that propagates outward as electromagnetic waves, carrying radio frequency (RF) energy. There are a few things we need to cover, so Here are some details for how this process works:
- Current Flow: When an RF signal is applied to the vertical antenna’s feed point, an alternating current (AC) flows up and down the length of the antenna. The amplitude of this current varies with the applied signal, causing it to oscillate.
- Electric Field: The oscillating current creates an oscillating electric field around the antenna. As the current changes direction, so does the electric field. This alternating electric field is responsible for generating electromagnetic waves.
- Magnetic Field: According to Maxwell’s equations, a changing electric field induces a magnetic field, and vice versa. As the electric field around the antenna oscillates, it induces a corresponding magnetic field that also oscillates.
- Electromagnetic Waves: The oscillating electric and magnetic fields are mutually reinforcing each other and propagate outward from the antenna in the form of electromagnetic waves. These waves consist of electric and magnetic field components that are perpendicular to each other and also perpendicular to the direction of wave propagation.
- Radiation Pattern: The shape of the vertical antenna and the frequency of the RF signal determine the radiation pattern – the directional pattern in which the electromagnetic waves are emitted. Vertical antennas are typically omnidirectional, meaning they radiate equally in all horizontal directions. This makes them suitable for applications like broadcasting and mobile communication, where coverage in all directions is desired.
- Ground Reflection: In addition to the direct radiation from the antenna, ground reflection can also play a significant role, especially when the antenna is located close to the ground. The ground beneath the antenna reflects some of the radiated energy, reinforcing the signal in certain directions and causing constructive and destructive interference patterns that affect the overall radiation pattern.
In summary, a vertical antenna will radiate electromagnetic waves because of the oscillating electric current flowing up and down its length. This current will generate an alternating electric and magnetic field, which combine to form electromagnetic waves that propagate outward. The shape of the antenna and its surroundings determine the specific radiation pattern. Higher is better, so if you want to get long distances you need to put the antenna up as high as you can, in order to get as large a Line-of-Sight as possible. So there you go, that’s a short explanation of how a vertical antenna radiates. 73.