I guess "Gordo" never read any of the Antenna Engineering textbooks!
The Handbook of Antenna Design Vol 2, Alan Rudge:
"The radial ground system and the ground surrounding it, within a radial
distance of a wavelength or so, are effective in determining the
terminal loss resistance. This is not the situation for launching of
skywaves. the reduction in the skywave field strength because of the
imperfectly conducting curved earth is influenced by the ground well
beyond the ground screen; in fact, for radiation angles less than 5
degrees above the horizon, the ground conductivity fifty or more
wavelengths in front of the antenna is effective in determining the
vertical radiation pattern.
Thus, while the terminal-loss (ground-loss) resistance limits the total
power radiated, and hence the field strength at a particular radiation
angle, the shape of the vertical pattern is determined by the ground in
front of the antenna far beyond the limits of the antenna and its radial
ground system."
Read it for yourself; page 574 here:
http://books.google.co.uk/books?id=QjYtNJZmWLEC&pg=PA574&lpg=PA574&dq=vertical+antenna+ground+radials+reflections&source=bl&ots=XpdSwsNx12&sig=3x5HxNPe8lKjJ8RIWi0HJ5p06Q0&hl=en&ei=6qAlTe_GII-1hAezm9TtAQ&sa=X&oi=book_result&ct=result&resnum=15&ved=0CIUBEOgBMA4#v=onepage&q&f=false
73,
Steve G3TXQ
|