Few aircraft have "receive only" radios, most have full Transceivers. For redundancy they have multiple Transceivers, and most military radios cover both VHF a

Few aircraft have "receive only" radios, most have full Transceivers. For redundancy they have multiple Transceivers, and most military radios cover both VHF and UHF. For safety and redundancy the pilots can receive and transmit on any of their multiple radios just by (selecting the appropriate frequency) and pressing the appropriate Receive/Transmit selector buttons. Many military aircraft also have secure (spread-spectrum) transceivers as separate units. Many aircraft that fly over water also have VHF Marine radios fitted.