Definition
A specific radio frequency, 225 megahertz, that marks the lower edge of the Ultra High Frequency (UHF) band used for military aviation voice communications. Frequencies at and above 225 MHz fall within the UHF aviation band; frequencies below it do not.
Plain English
225 MHz is a specific point on the radio dial. It's the bottom of the range used by military aircraft to talk on their radios.
Context Anchor
Seen in radio communication discussions, especially where UHF or military aircraft frequencies are mentioned.
Derivation
MHz stands for megahertz, meaning one million cycles per second. 'Mega' comes from Greek 'megas' meaning 'large,' and 'hertz' is named after Heinrich Hertz, the physicist who first demonstrated radio waves. So 225 MHz means the radio wave cycles 225 million times per second.
Why Pilots Care
Civilian aircraft typically use VHF radios (around 118 to 137 MHz). Military aircraft use UHF radios starting at 225 MHz. Knowing this boundary helps pilots understand why they may not be able to reach a military controller on a civilian radio, or vice versa.
Intuition Check
225 MHz is not a distance, altitude, or channel number by itself. It is an exact radio frequency that the radio must be able to tune.
Example Sentence 1
Military aircraft operate on UHF frequencies from 225 MHz up to 400 MHz.
Example Sentence 2
During the exercise the aircraft monitored 225 MHz to receive real-time traffic advisories from the joint operations center.