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Roy Lewallen wrote:
But as some others have commented, it's much more common to take care of the capacitive reactance of a short whip with a series, rather than shunt, inductor. Quoting the ARRL Antenna Book: "The input impedance of short, high-Q coil-loaded antennas is quite low. For example, an 8-foot antenna optimized for 3.9 MHz with a coil Q of 300 and a ground loss resistance of two ohms has a base input impedance of about 13 ohms." It is common practice to adjust the feedpoint impedance to about 13-j22 and install a base shunt inductive reactance of ~+j30 to twist the feedpoint impedance to a near perfect 50+j0 ohms. -- 73, Cecil http://www.w5dxp.com |
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