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Dr. Slick wrote:
"What does it say?" I don`t have Kraus, unfortunately. I do have Arnold B. Bailey`s "TV and Other Receiving Antennas". Bailey covers more antenna territory than most, and does an excellent job of it. Bailey also includes a catalog of antenna types, all sized for 200 MHz for easy comparison. Bailey says the surge impedance of an antenna is inversely proportional to the capacitance per unit length. Reminds one of a transmission line. This is non-uniform, so Bailey has an empirical equation which says the larger the periphery of the rod, ther smaller the average surge impedance. The ratio of the electric field to the magnetic field surrounding an antenna must be related to the ratio of volts to amps in the antenna wire (the surge impedance). The surge impedance of a thin-wire 1/2-wave dipole from page 500 is 610 ohms (average). The surge impedance of a fat-cylinder 1/2-wave dipole from page 502 is 240 ohms (average). Pattern and gain are identical for both antennas. But, Dr. Slick may be on to something after all. The bandwidth of the fat antenna is about 3X that that of the thin. In antennas, bandwidth is often an indicator of match. Best regards, Richard Harrison, KB5WZI |
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Conservation of Energy | Antenna |