An antenna is a type of tuned circuit consisting of both capacitance and inductance. At resonance, capacitive and inductive impedance are equally balanced - in a sense canceling each other out. At this point the antenna appears to be entirely resistive. The apparent resistance is a combination of loss resistance (for example in the feedlines and antenna elements) and radiation resistance.
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 resonant 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.
|Physical quantities||Current * Gain * Impedance * Power * Q of a circuit * Radiated Power Measurement * Reactance* Resistivity * Resonance * Voltage|
|Components||Baluns * Bipolar-Junction Transistors * Capacitors * Diodes * Inductors* Lasers * Microphones * Resistors * Transformers * Wire|
|Circuits||Attenuators * Digital Signal Processing (DSP) * Dummy load * Filters * LC filters * Power Supply Design * Rectifier Circuits|
|Design||Amplifier Design * Oscillator Design|
|Electromagnetic Waves||Relative power (Decibels) * Harmonics * Interference and BPL|