[TowerTalk] more on NVIS

[Jim Lux]

There's an interesting article at:
http://www.gordon.army.mil/AC/Fall02/BCTSOP2.htm

which discusses various HF comm modes, with a fair amount of detail on 
NVIS.  In particular, go about 2/3 of the way down to where they start 
talking about horizontal dipole antennas.  There's a chart showing 
performance (straight up) for halfwave dipoles over "average" and "perfect" 
ground at various heights and frequencies (all the way down to 0.1 ft). and 
a discussion of preferred heights (30 ft is recommended)
http://www.gordon.army.mil/AC/Fall02/dffig15.jpg