For use in logging a borehole through various formations of the earth, the preferred and illustrated embodiment of an RF transmitter system including antenna placed in the sonde is disclosed. The embodiment sets forth a pair of dipole antennas mounted in a closed chamber on a central support. The chamber is in a cylindrical housing filled with a high dielectric material. The antennas are bowtie dipoles which are fed with separately time delayed pulses (preferably having waveforms of only one cycle) so that the relative time delay between the two antenna inputs and the propagation velocity in the high dielectric medium results in reinforcing addition of the radiated wave in the forward direction and destructive cancellation in the reverse direction to provide a directional azimuthal radiation pattern. The housing is rotated at a slow rate to enable pulses to be transmitted in various directions to map the formations near the borehole.
Bob M. Duff