To use the applet type in new values in the width and thickness fields, and click the calculate button. You must click the calculate button for the new values to take effect. The self impedance equivalent diameter that you would use in antenna modeling is calculated, and the equivalent diameter for the r.f. resistivity is calculated as well. Be sure to use the same units for width and length that is both in millimeters, or both in inches etc. The equivalent diameters will be in the same units.
The plot on the right displays the calculated current distribution around the conductor in red. Zero on the x axis of the plot is the center of the wider dimension I'll assume that is the width. Larger x is moving along the perimeter of the conductor so the corner is at x=width/2. The current density diverges there (but the total current is of course finite) as is well known. Larger x values correspond to moving along the shorter side. Again only half the thickness is shown. The current on the other parts of the surface are given by symmetry. The blue line is the value of current that would occur if the same total current flowed uniformly around the surface.
The expressions used and their derivation can be found at Approximate R.F. Resistance of Rectangular Cross Section Conductors or Download PDF file and Analytic expressions for the equivalent diameters of rectangular cross section conductors or Download PDF file
Here is the Java source code for this applet, http://fermi.la.asu.edu/w9cf/equiv/equivsrc.zip .
To run applet locally without downloading and compiling the source, you can download the java class files from http://fermi.la.asu.edu/w9cf/equiv/equiv.zip and unzip that file in any convenient directory on your system. Also download the file you are looking at now http://fermi.la.asu.edu/w9cf/equiv/index.html. You can use the save as function of your browser. Call this file index.html, and place it in the same directory that you unzipped equiv.zip in, and point your browser at it.w9cf home