The images that follow show the near field Z as a measure of mismatch to 377 Ohms of free space. The coloring shows the contours of SWR averaged through the depth of a half wavelength sided cube. The degree of mismatch has been limited to display the values of 1:3:1 SWR. In other words, Z values outside the range of roughly 120 Ohms to 1200 Ohms are clipped so that extreme values did not drive the graphics presentation. The Blue coloring below corresponds to a SWR of 1.25.
The notable side views of the Quarter Wave Monopole reveal two structures. As this is a SWR based valuation, it is not obvious that the SWR of the lower structure is due to less than 377 Ohm fields and that the SWR of the upper structure is due to greater than 377 Ohm fields. However, considering the general observation of I/E Standing Waves on the antenna, these fields closely correlate.
download the mathcad file used to generate the images.
download the eznec file used to generate the data.
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