Originally Posted by
Jan Olieslagers
As I remember, a "channel" as used in marine VHF consists of two frequencies, so that they can have duplex communication, which we poor aviators cannot. Even not in the days of 8,33 kHz
Some marine VHF channels are composed of a pair of frequencies to allow the use of repeaters located on high ground to extend range. Aircraft don't generally need to use repeaters. since you're supposed to already be above the highest ground most of the time!