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Decerning antenna impedance
Anyone here know of a formula or other manner in which to determine the
impedance of a wire antenna, knowing it's length and height above ground? Brian |
#2
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Sorry, can't spell today. Should've been discerning I believe.
"Brian" wrote in message hlink.net... Anyone here know of a formula or other manner in which to determine the impedance of a wire antenna, knowing it's length and height above ground? Brian |
#3
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In article k.net,
"Brian" wrote: Anyone here know of a formula or other manner in which to determine the impedance of a wire antenna, knowing it's length and height above ground? Z = 138log(4H/D) Z is in ohms H is the height of the wire above ground in feet. D is the diameter of the wire in inches The length of the wire does not matter. This is Z is the result of electric field effects measured relative from earth ground. You can see by formula that the higher the wire is the higher the impedance and the larger the wire size the lower the impedance will be for the wire. A typical wire will represent hundreds of ohms. An 18 guage wire would be ~ 500 to ~ 600 ohms 5 to 15 feet above ground. -- Telamon Ventura, California |
#4
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"Brian" wrote in message hlink.net... Anyone here know of a formula or other manner in which to determine the impedance of a wire antenna, knowing it's length and height above ground? Brian A good source for these formulas is the ARRL antenna book. The ARRL radio amateur's handbook also has some antenna formulas, and is often found in public libraries. Here's a couple of radio amateur sites: http://www.cebik.com/radio.html Look for the "Practical Antenna Notes" Reg Edwards has written some computer programs which greatly simplify using some of the more complicated formulas. There are a few of them for antennas: http://www.btinternet.com/~g4fgq.regp/page3.html#S301" But the effects of the antenna's impedance are far more important when transmitting. As a practical matter, receivers work fine over a broad range of impedances. Frank Dresser |
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