Definition
The range of radio frequencies from 535 to 1705 kilohertz (kHz) used by commercial AM (amplitude modulation) radio stations. Non-Directional Beacons (NDBs) used for aviation navigation transmit on frequencies just below this band, typically between 190 and 535 kHz, and some NDB receivers can also tune into AM broadcast stations.
Plain English
The set of radio frequencies used by regular commercial AM radio stations, the same ones you'd hear in a car radio. NDB navigation equipment in aircraft operates on nearby frequencies and can sometimes pick up these stations too.
Context Anchor
Seen in discussions of non-directional beacon equipment and automatic direction finder receivers, where an aircraft can tune certain low-frequency and medium-frequency radio signals.
Derivation
AM stands for amplitude modulation, a method of encoding sound onto a radio wave by varying the wave's strength (amplitude). Broadcast band refers to the slice of the radio spectrum set aside for public radio stations.
Why Pilots Care
NDB signals share this band with commercial broadcasts, so pilots must account for possible interference when tuning for navigation.
Analogy
It is like using a familiar AM car radio station as a signal source, except the aircraft equipment is interested in the direction the signal comes from, not just the sound.
Intuition Check
Do not read “band” as a group of people or music. Here, “band” means a range of radio frequencies.
Example Sentence 1
The ADF receiver covers the lower frequency range used by NDBs and extends into the AM broadcast band.
Example Sentence 2
ADF equipment is designed to receive signals from the AM broadcast band for non-directional navigation.