Topband: Elevated Radials as a sub for the real thing?

[Dan Zimmerman N3OX]

>
> Do they distort the field pattern by acting like
> low dipoles, at least partially send radiation into the clouds above?


They don't act as dipoles because the current phase is such that current is
going out into both halves at one point in the RF cycle and back in toward
the feedpoint 180 degrees later.  Since they're phased like that, there is a
deep null overhead and lots of cancellation in all directions.

Four elevated radials have an 8-lobed radiation pattern 40-50dB down from
the total pattern, maxima pointing in these directions:
http://n3ox.net/files/elrad.jpg.  The radiation from the radials has a null
overhead just like the vertical does.

Efficiency concerns and common-mode concerns (like
http://www.w8ji.com/ground_plane_verticals.htm) need to be addressed, as
does near field coupling of elevated radials to unwanted stuff.  Far field
radiation from elevated radials, though, is probably not an issue provided
the current balance in the radials is good (maybe not a given?)

73,
Dan