Near Vertical Incidence Skywave (NVIS) is a propagation mode which uses high angle radiation to
send signals almost straight up to be reflected back to Earth for very effective short to medium
distance communications. This mode of
operation makes it ideal for in-state
communications during disasters or other
emergency situations. The military has used
NVIS techniques for decades to provide short
haul communication with other units on the
NVIS only works at frequencies from 2 MHz
to 10 MHz. The signal must penetrate the D
layer of the ionosphere, and bounce off the F
layer. Lower-frequency signals will not
penetrate the D layer; higher frequencies will
not bounce off the F layer at these sharp angles and just goes out into space. CLICK ANTENNA TO THE LEFT FOR DOWNLOAD

Click the link to know more about signals, angles and take off.
3 2 1 take off! Where ya go, how far is it?