Unfortunately, the "artificial ground" is just as much an antenna as the
"antenna" is. And it's usually in a lousy place for an antenna -- often,
low and parallel to the ground. If it is, the radiation from the
"artificial ground" (representing a sizeable fraction of the RF power
your rig is producing) will be largely absorbed by the ground. If it's
in a more favorable spot, its radiation will end up modifying your
overall radiated pattern.

Just because we connect one wire to one terminal of our rig's output and
call it an "antenna" and connect the other to the other terminal and
call it "ground" doesn't impart any magical properties to them. They
behave just the same.

Roy Lewallen, W7EL

K9SQG wrote:
A more common use of an artificial ground is to "tune" a dc ground lead so that
it is also at RF ground. This helps to keep the solid state rigs contented but
in no way has an effect on radiation properties of the antenna in most cases.