Rik,

You have a novel idea.  There could be problems of transients with the
"synchronous switch" needed to make and break during each RF cycle.  Most
antennas work in "steady state mode" where the energy has time to reflect
and establish a "standing wave pattern", and related wavefronts in space
around the antenna.  Your idea involves a rather interruptive action and
would seem to reduce the scope for stored energy in near fields.

73, Bob

73, Bob