Resonance

Related wiki pages: Antenna, capacitance, inductance

An antenna is a type of tuned circuit consisting of both capacitance and inductance. At resonance, capacitive and inductive impedace are equally balanced - in a sense cancelling each other out. At this point the antenna appears to be entirely resisitive. The apparent resistance is a combination of loss resistance (for example in the feedlines and antenna elements) and radiation resisitance.

File:Vk4yeh antenna resonance.jpg

The inductance and capacitance of an antenna are determined by a number of factors, including construction materials, height above earth, and its dimensions. Of these, dimensions are usually the major feature affecting reonant frequency. For example, operating on HF requires an antenna with much larger elements that when operating on VHF.

Ideally, antennas are operated close to their resonant frequency. However, this would effectively result in a limited bandwidth being available for use.

Possible solutions to this problem are to use a "thicker" element, or to use a different antenna type.