Definition
Operating or responding equally well in two opposite directions. In the context of an ADF loop antenna, a bidirectional pattern means the antenna receives signals with equal strength from two opposite directions, producing two nulls and two peaks 180° apart rather than a single unique direction.
Plain English
Working in two opposite directions at once. For an ADF antenna, it means the antenna can't tell whether the signal is coming from straight ahead or straight behind — both directions look the same to it.
Context Anchor
Seen in ADF component discussions, especially when describing how an ADF antenna receives signals from a ground radio station.
Derivation
From Latin 'bi-' meaning 'two' and 'directio' meaning 'a directing or pointing.' Literally 'two-directional.' Knowing the 'bi-' part comes from 'two' helps lock in that this isn't about all directions or any direction — it's specifically about two opposite ones.
Why Pilots Care
A bidirectional loop antenna alone gives an ambiguous result — the station could be ahead or behind. That's why ADF systems pair the loop with a sense antenna to resolve the ambiguity into a single bearing. Understanding 'bidirectional' explains why ADF needs both antennas to work.
Intuition Check
Bidirectional does not mean two-way communication here. It means the antenna receives or responds in two opposite directions.
Example Sentence 1
The loop antenna in an ADF system has a bidirectional reception pattern, so the receiver cannot tell on its own whether the station lies ahead or behind the aircraft.
Example Sentence 2
Pilots must resolve the bidirectional ambiguity of the loop antenna before the ADF can display the correct bearing.