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![]() Alhearn If it is "understanding" that you want, I'd suggest you plot the antenna's impedance on a Smith Chart. A plot of an antenna's impedance with varying frequency will describe a continuous curve. Beyond that, any additional comments would probably just make this post more confusing. I'd bet you can answer your own question after looking at a Smith Chart. Note the chart identifies R+/-jX. So the reactance added in series will move an impedance along lines of constant R. The path of the impedance plot resulting from shunt X can also be identified, but maybe thats for another time for discussion Jerry "alhearn" wrote in message om... In my dipole/vertical modeling and analyzer measurements, as frequency is increased past quarter-wave resonance, I've noticed with interest that both reactance and resistance peak at different times, as they increase with frequency toward the half-wave point. Resistance peaks at approximately the half-wave point as expected, but inductive reactance always peaks a little earlier (lower frequency). This is also indicated in the ARRL Antenna Book in Figures 3 through 5 on pages 2-3 and 2-4 (it's the bulging on the right side of each of the curves). For a given antenna of particular length, adding inductive or capacitive reactance changes the magnitude of the reactance peak, but not the frequency at which it occurs. Changing the thickness of the radiating elements changes (lowers) the frequency at which the reactance peak occurs, but it also changes (lowers) the frequency at which resistance peaks, and the difference in these two freqencies stays approximately the same. Why does the reactance peak occur slightly earlier than half-wavelength? Can it be mathmatically predicted/explained? Any help would be appreciated. Al, WA4GKQ |
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