Definition
The radio frequency band, in the C-band portion of the microwave spectrum, allocated for the angle-guidance signals of the Microwave Landing System (MLS). Within this band, 200 separate channels are available for assignment to MLS approach azimuth and elevation transmitters at airports.
Plain English
This is the slice of radio frequencies set aside for the Microwave Landing System to send its approach guidance signals to aircraft. There is room within it for 200 different channels, so many airports can run an MLS without their signals interfering with each other.
Context Anchor
Seen in instrument approach guidance discussions, especially when comparing MLS guidance with other landing guidance systems.
Derivation
MHz stands for megahertz, meaning millions of cycles per second. The number tells you how many times the radio wave oscillates each second. Frequencies in this range fall within what is called the C-band of the microwave spectrum, which is well above the VHF band used for ILS localizer signals.
Why Pilots Care
Knowing that MLS operates in this band helps pilots understand why MLS uses different airborne equipment than ILS, and why each MLS approach has its own channel number that must be selected on the receiver before the signal can be used.
Analogy
Think of it like a reserved lane on the radio dial. MLS equipment uses this lane so its approach guidance signals can be sent and received without being mixed up with unrelated radio signals.
Intuition Check
Do not read 5031 to 5091 MHz as an altitude, heading, or distance. Here it is a frequency range: a specified part of the radio spectrum used to carry guidance signals.
Example Sentence 1
The MLS approach azimuth station transmits in the 5031 to 5091 MHz band, with one of 200 channels selected for that airport.
Example Sentence 2
Ground equipment transmits azimuth signals across 5031 to 5091 MHz to keep the aircraft aligned with the runway centerline.