RT high tone carrier wave on UAL?
During the last couple of years while flying, I noticed that all transmissions of United airlines have a distinct carrier wave. Some sort of high monotonous tone in the background. (About 150 hertz).
Why is that? And why only with that airline?
I must say that in the airspace that i work in, all ual flights are wide bodies. (Europe)
If someone knows, i would be delighted.