A decoupled, ultra wide-band, transmitting-and-receiving, planar dipole antenna is designed and constructed for the use of the continuous electromagnetic wave subsurface interface radar in the frequency range from 10 MHz to 150 MHz. Two planar dipoles separated about 1 meter are located inside a dielectric slab covered by a conducting plane on the top side and separated by an air gap from the bottom ground interface. Its decoupling is due to a cut-off nature of the slab waveguide. Due to a limitted size of the antenna, 15m X 1m X 0.1m, the coupling between the transmitting and the receiving dipoles is measured by less than -70 dB over the frequency from 70 MHz to 150 MHz. A metal pipe of its diameter of 0.276 meter burried in a soil in the depth of 1 meter is detected with the signiture of the double dip of -15 dB at 150 MHz.