2 adjectives to describe antenna

There was a long pause; Pendleton, during this, grew sensible of a long, wavering mental antenna which he projected into the shadows; and its delicate sensitiveness told him of the silent approach of a fearful thing.

Soon I'm in the depths of a dark, sweet sleep; my ears alone keep watch and turn like sensitive antennas towards vague sounds of doors and bells ...

2 adjectives to describe  antenna