Readme.txt for Smith3D.zip

Smith3D.zip contains files pertaining to "Creating 3-D Antenna Radiation-Pattern Plots," by Doug Smith, KF6DX (QEX, July/August 1999, pp 40-43). 3Dplot.Bas and 3Dplot.exe are the author's files that plot the sample data file, 10m3el.log, on a computer screen. On my computer, 3Dplot.exe gave an error. I made a simple change to plot the example on my computer and named the changed source and executable files 3Dplot1.bas and 3Dplot1.exe. Cover.tif shows the correctly drawn result. The source (.bas) files were made with Microsoft's QuickBasic 4.5 programming environment and compiled with the BC7 compiler. The compiled (.exe) versions should work on DOS versions 4.0 and later, or in DOS windows.

73, Bob, KU7G


Robert J. Schetgen, KU7G/1				American Radio Relay League
Senior Assistant Technical Editor				225 Main St
QST Team 						Newington, CT 06111-1494
Hints & Kinks Editor   	
QEX Managing Editor					e-mail: rschetgen@arrl.org  
ph: 860-594-0277 (direct)					fax: 860-594-0259

Have you seen the new QEX? Wow! Check it out at http://www.arrl.org/qex/


Appendix 
Experience compiling and running my BASIC program under QuickBasic 4.5 and VisualBasic 1.x prompted me to add a few notes about the limitations of the program, as well as some peculiarities of the MININEC-generated data files.
To avoid gaps in memory allocation, QB 4.5 indicates that integer arrays ought to be dimensioned to integral-power-of-two sizes, eg, 16,384. In at least one instance, we were stopped by a "subscript out of range" error as soon as we added buffers for other functions, such as disk navigation for the input file. Various versions of BASIC, especially those running under Windows or other multitasking operating systems, may react differently. I suggest redimensioning the large arrays to the minimum size necessary for your applications.
Some antenna modeling software may not write data files that contain all the information required to produce a 3-D plot. Others may not format the data precisely as shown in my example. You programmers will see that my program is not particularly flexible in handling alternate data file formats, but you will also see that the parsing routines are easily modified.
Most modeling software writes a zenith angle that is 90? minus the actual zenith angle. My program assumes this. Also note that the data file representing an entire above-ground pattern can be generated in two ways: (1) Use a zenith angle range of 0-90? and an azimuth angle range of 0-360?, or (2) use a zenith angle range of 0-180? and an azimuth angle range of 0-180?. The same idea applies to free-space patterns. Unexpected things occur when the data file contains overlapping pattern segments, or when the data are ambiguous because of weird angle-range settings.
So please view my program as a sort of example, and not as a finished product. Thanks to Managing Editor Bob Schetgen, KU7G, an accomplished programmer, for valuable feedback and assistance.-Doug Smith, KF6DX

QEX 7/99 / 3D Appendix / Smith / RS 	p 1 of 2
Filename: C:\My Documents\QEX\7x99\Smith 3D\3D Appendix.doc	printed 8-Jun-99 05:04 PM