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 one 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 Discone is driven at 20M for the first set of images. Note how the fields closely conform to the shape of the Discone, even down to the detail of the disk and cone shape being sharply delineated here.
download the mathcad file used to generate the images.
download the eznec file used to generate the data.
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This is the discone driven at 10M. Note how a flare of SWR appears over the Disk. This structure has the appearance of a vertical's fields. Another, more distinct attribute is the wring of SWR presented in the XY view of the fields (StandingZWave).
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