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![]() "Cecil Moore" ha scritto nel messaggio ... A 1/4WL monopole is half of an antenna. The ground plane is the other half. The feedpoint is at a current maximum point which is a magnetic field maximum. The high intensity magnetic field directly encountering the earth is a lossy condition. A 1/2WL monopole is a complete resonant antenna. The feedpoint is at a voltage maximum point which is an electric field maximum. A pure electric field encountering earth ground is less lossy than a pure magnetic field encountering earth ground. Since the feedpoint impedance is very high, some hams simply use a ground rod for a counterpoise. First thanks for replies abt the 5/4 WL monopole, i'm trying right now to use eznec and simulate what you saw me. One more newbie question: 1/4 WL and 1/2 WL monopoles are both end feeded. So my feed point is exactly at the begin of monopole. Assuming there is no feed line, or also a 1/2 WL feed line (if IIRC 1/2 wl is the line lenght that preserve the phase of my RF wave from generator to the end of the line...) what decide if i'm feeding the antenna on a current maximum point or in a voltage maximum point ?? On a dipole, with the imagine of the wave "superimposed" to the dipole in my mind, is quite easy for me figure out if i'm feeding it on a current node or on a voltage peak (e.g center feed vs. off center feed dipole). But since in both 1/4 and 1/2 wl monopoles i'm at the *begin* of the antenna, what decide the feed point modality (I or V) ?? The impedance i have at the specific point ?? Regards, -.-. --.-., Cristiano, Italy. |
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