Method and apparatus for downhole signal communication and measurement through a metal tubular

A method for transmitting and/or receiving a signal through an earth formation, comprising:

• a) drilling a borehole through the earth formation with a drill string, the drill string including a sub having an elongated body with tubular walls and including at least one station having at least one slot formed therein, each at least one slot fully penetrating the tubular wall to provide a continuous channel for the passage of a signal, the sub including barrier means within the central bore to provide a pressure barrier between the interior and exterior of the tubular wall at the at least one slot;
• b) disposing a run-in tool within the sub, the run-in tool being adapted with signal transmitting means and/or signal receiving means;
• c) disposing the run-in tool within the sub such that at least one signal transmitting or receiving means is aligned with at least one slotted station on the sub;
• and
• d) transmitting or receiving a signal through the formation, respectively via the transmitting or receiving means.

A method for measuring a characteristic of an earth formation surrounding a borehole, comprising:

• a) adapting a downhole tool with at least one signal transmitting means or at least one signal receiving means;
• b) adapting the downhole tool with end means capable of accepting a fishing head or a cable connection;
• and
• c) disposing the tool within a sub on a drill string to measure the formation characteristic, utilizing the transmitting or receiving means, as the drill string traverses the borehole, the sub having an elongated body with a central bore and including at least one slot formed therein to provide a channel for the passage of a signal and barrier means within the central bore to provide a pressure barrier between the interior and exterior of the sub at the at least one slot.