How about the USGS 1 and 3 meter DEM's
These digital 'maps' provide improved vertical resolution. There are holes in the DEM data base. I personally think they are difficult to load in RadioMobile. W4xxx indicates a good program to download them with and to convert them to a format that HFTA can use is MicroDEM. It is free and available at http://www.usna.edu/Users/oceano/pguth/website/microdemdown.htm This is a 40 Mb download (25 of which are the Help files).
Where can I get RadioMobile? The link in the article does not appear to work.
Try http://www.cplus.org/rmw/english1.html It appears the address changed since press time, the page you go to is in French and it is possible to get to the RadioMobile page; this is easier. RadioMobile is NOT an easy program to use. It is very counter-intuitive, however, if you stay with it, you will probably be pleased. If you need help, there is a pretty good tutorial at http://pizon.org/rmw/