In its second printing, the companion software for the 18th edition of The ARRL Antenna Book was updated. Owners of the first printing can download a patch that will update the two affected programs, YT and TLA. (Note: This patch is unusable unless you have the software from the 18th edition, first printing.)
Not sure which printing of the 18th edition you have? Look at the copyright page (this is page ii, which immediately precedes the Foreword). Near the bottom of the box containing the copyright notice you'll see "18th Edition" followed by either "First Printing" or "Second Printing." If you installed the software that came with the second printing, you do not need this patch; you already have the up-to-date version.
To use the patch, download the patch file and run it. It is a self-extracting file that will produce the files: README.1ST, PATCHTLA.EXE and PATCHYT.EXE. Follow the instructions in the README.1ST text file to install the patches.
Read the README.1ST file
Download the patch file, AB18P2.EXE [114,424 bytes]
ARRL has significantly enhanced the elevation-angle statistical files for YT, the "Yagi Terrain analysis" program bundled with the 18th Edition of The ARRL Antenna Book.
The first two printings of the 18th Edition of The ARRL Antenna Book had several errors in Figures 65 and 66 in Chapter 6. The following files are corrected versions. The CD-ROM version and the third printing of the book have the correct schematics. Both corrections can be downloaded (63,401 bytes) in Adobe PDF format.
In Chapter 18, table 6 has some values printed incorrectly. Figure 28 has also been clarified. Both corrections can be downloaded (62,701 bytes) in Adobe PDF format.