Silmukkaantenniä

Silmukkaantenniä, often translated as loop antenna, is a type of radio antenna that consists of a closed loop of conductive material, typically wire or tubing. The shape of the loop can vary, with common forms including circular, square, and triangular. The size of the loop is a significant factor in its performance, often being resonant when its circumference is approximately one wavelength of the radio frequency it is designed to receive or transmit.

Loop antennas are broadly categorized into two main types: small or resonant loops and large or full-wave loops. Small loops, where the circumference is much smaller than a wavelength, are typically less efficient but can be useful for their compact size and directional properties. Resonant loops, with a circumference close to a wavelength, are generally more efficient and offer gain over a simple dipole in certain directions.

The radiation pattern of a loop antenna depends on its size and how it is fed. A small loop typically radiates a pattern with maximum radiation perpendicular to the plane of the loop, functioning as a magnetic dipole. A full-wave loop, on the other hand, can exhibit a more complex radiation pattern, often with broadside radiation if fed appropriately. Loop antennas are known for their relatively narrow bandwidth, meaning they operate most effectively over a limited range of frequencies. They can also be useful for their rejection of vertically polarized signals when oriented horizontally, making them suitable for reducing certain types of radio interference. Applications include amateur radio, shortwave listening, and some commercial broadcasting.