Antennas: Difference between revisions
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[http://www.hamuniverse.com/n4jaantennabook.html UNDERSTANDING ANTENNAS FOR THE NON-TECHNICAL HAM] | [http://www.hamuniverse.com/n4jaantennabook.html UNDERSTANDING ANTENNAS FOR THE NON-TECHNICAL HAM] | ||
Any person who wants to build there own antenna and needs to find parts and alluminum tube can contact Brian on 0402 930 581. There is a large selection of drawn telescopic tube in imperial and metric sizes plus masts and poles in stock. |
Revision as of 22:40, 3 April 2009
Related wiki page: Feedlines, Capacity Hats, Antenna Design, Gain, Bands, SWR, harmonics, Front-to-back ratio Electromagnetic Waves, Radiated Power Measurement
Antennas are electrical circuits designed to facilitate the transmission and/or reception of electromagnetic radiation.
Antennas are specifically designed to transmit/receive as much electromagnetic radiation as possible, whereas most circuits are designed to emit/detect as little as possible. However, even a dummy load will emit a small amount of electromagnetic energy when radio-frequency oscillations are applied to it.
Antenna Size
Optimized antennas will have dimensions of the same order as the wavelength of operation. A balanced antenna will typically be about a half-wavelength long, and an unbalanced antenna such as a vertical will typically be about a quarter-wavelength long. It is possible to shorten antennas drastically at the cost of efficiency. See antenna loading for more discussion.
Theory of Antennas
In terms of their construction, antennas are RLC circuits in which resistance, inductance and capacitance are distributed along a conductor, rather than being concentrated in a particular component such as an inductance in an inductor.
The "ideal" antenna will be resonant for the frequency it is used at. In practical terms, this is impossible unless only a limited number of frequencies are used all the time.
Hence antenna design is a compromise, but good results can be achieved if we understand the notion of harmonics.
Antenna Types
Simple Antennas:
Complex Antennas:
Specialized Antennas:
Baluns
Understanding Antennas
UNDERSTANDING ANTENNAS FOR THE NON-TECHNICAL HAM
Any person who wants to build there own antenna and needs to find parts and alluminum tube can contact Brian on 0402 930 581. There is a large selection of drawn telescopic tube in imperial and metric sizes plus masts and poles in stock.