Definition
The upper frequency limit of the civil aviation VHF communications band. Aircraft VHF communications radios are designed to operate from 118.000 MHz through 136.975 MHz, with channel spacing of 25 kHz or, on 8.33 kHz-capable radios, narrower increments within the same band.
Plain English
It is the highest radio frequency in the band that pilots use to talk to controllers and other aircraft. Any standard aircraft VHF radio can tune up to this number but no higher.
Context Anchor
Seen when discussing aircraft navigation and communication radios, especially the range of frequencies a VHF communication radio can tune.
Derivation
MHz stands for megahertz, meaning one million cycles per second. It describes how many times per second the radio wave oscillates. A higher number means a higher-frequency wave.
Why Pilots Care
Knowing the band's upper limit confirms whether a frequency assigned by ATC or shown on a chart will tune on the radio. Anything above 136.975 MHz is outside the civil aviation comm band and will not be a normal ATC or air-to-air frequency.
Intuition Check
Do not read 136.975 MHz as an altitude, code, or navigation setting. In this context, it is a voice radio frequency.
Example Sentence 1
The aircraft's communications radio tunes from 118.000 to 136.975 MHz, covering the full civil aviation VHF band.
Example Sentence 2
During preflight, the crew verified that 136.975 MHz was within the operational band of both VHF transceivers.