"Roy Lewallen" wrote in message
...

Declaring a vehicle to be "ground" doesn't give it magic properties. It's
a conductor, just like the antenna. Exactly the same current that flows
upward on your antenna flows downward along your vehicle. The vehicle and
"antenna" comprise an asymmetrical dipole, and neither half is inherently
more or less important than the other.

Roy Lewallen, W7EL


That is rather simplistic and not reality reflecting explanation.
Like saying that ground plane, vertical antenna is a dipole.
Vehicle body represents "ground plane" similar to two or more radials. The
current flows along the surface of the vehicle, just as along the more
elaborate ground plane consisting of more than say 8 radials. Cancellation
of current along the body happens, just like in opposite radials in GP.
Radiation pattern is formed between the RADIATOR (whip) and GROUND PLANE
(vehicle body).
Additional effect is that vehicle "ground plane" is capacitively coupled to
the ground and this is reflected in changes in efficiency depending on the
surroundings ground conditions (salty, wet ground, reinforced concrete
bridges, etc.)

As far as I understand, dipole refers to dual pole antenna with symmetrical
current distribution. Vertical antenna mounted on conducting body of vehicle
has current distribution in the "other pole" far from symmetrical. This can
be seen in modeling in EZNEC. Try to compare vertical whip mounted on
vehicle, with dipole that has one leg horizontal and you will see the
difference, far from "nice dipole" antenna.

So as soon as we have more than one radial, and some (horizontal)
cancellation is happening it ain't no dipole. It is monopole forming
vertical pattern against the ground plane (radials, vehicle body).

That's the way I understand it, without involving photons, Gaussss and other
farticles :-)

73 Yuri, K3BU