change is even more profound it is apparent that a combination of different depths of investigation allows differentiations of geological formation at different radial distances the modular design makes it easy to configure the tools for different array spacing further the use of one or more tri axial antennas as transmitters and or receivers increases the spacing that may be achieved which provides a corresponding increase in doi some embodiments of the invention relate to resistivity array designs having transceiver antennas in these tools the antennas are not designed as separate transmitters or receivers instead the same antenna can function as either a transmitter or a receiver such enhancement besides being economically advantageous allows more depths of investigation for the same number of subs as illustrated in fig3 fig3 shows a tool assembly 40 having three subs 41 42 43 that form two arrays with spacing of d and dx 2 because the antennas 41 and 43 can function as a transmitter or a receiver a third array having a spacing of dx 3 is also available with this tool configuration moreover with the transceiver antennas directional measurements can also be performed without having to have both transmitter and receiver belonging to a common downhole tool for example a set of symmetrized measurements may be obtained first with antenna 41 as the transmitter and antenna 43 as the receiver then with antenna 43 as the transmitter and antenna 41 as the receiver some embodiments of the invention relate to tools having.