With the sense antenna OFF (button not pushed), there should be a very sharp null off
the ends of the ferrite rod. Signals should drop at least 20dB over a very narrow range
of directions. Turn it slowly. (They are designed for the null to be detected by ear, but
might require adjustment of the gain control.) If you are outside with a vertical wire and
you can hear the signal, then you should have a null unless there is a lot of metal in the
area. That null should be bi-directional, off either end of the ferrite rod.
I'd try it also at various distances, making sure that your wire is vertical.
Or it could be that something isn't wired properly inside...
Once you get that working we can discuss adjusting the sense antenna to resolve the
bidirectional ambiguity of the loop by itself.