Figure 1-12. Response pattern for a bar antenna.
If we had some sort of compass or direction indicator on the radio we would have a complete
direction finder. There is one other factor to be considered. We have two possible directions
to choose from. This is the bidirectional ambiguity (the hard way to say it)(See Figure 1-13)
which must be resolved (you must make a choice) for accurate direction finding. To do this
we must add the signal input of another antenna (sense antenna) to the directional antenna
giving us a cardioid (heart-shaped) pattern. This takes away one of the nulls, allowing us to
decide which direction to choose. (See Figure 1-14).
Figure 1-13. Example of bidirectional ambiguity.