When an aircraft is in the air, it's usually up above any nearby trees and buildings within a matter of seconds from leaving the runway. The transmitters are strong enough that they can typically overcome whatever few obstacles may exist on the field and ATC's antennas are generally placed so as to minimize obstructions between those antennas and where airplanes will normally be on the field. Stations that are both at the same airport usually don't have much blocking their signals to each other. Conveniently for ATC and pilots, controllers and pilots (or pilots and other pilots) who are talking to each other are usually either on the ground at the same airport or one or both are in the air. The VHF signals used primarily for aviation radios generally have poor penetration of, well, pretty much everything except for the atmosphere. The audio as heard by pilots and controllers is indeed generally much better, but it's not usually due to some complex network of transmitters for the same frequency or even entirely just due to better equipment (though the latter certainly helps.) The main reason for the difference is line-of-sight. More than one transmitter on the same frequency causes problems, in that the signals will interfere with each other and that interference will vary depending on the location of the receiver, so multiple transmitters on the same frequency aren't (intentionally) used much. Indeed, most ATC frequencies have just one antenna, as a controller has noted in the comments. Controllers and pilots usually don't have much trouble hearing each other unless there are multiple stations transmitting on the same frequency at once or there's something like a mountain in the way (or possibly a building in the case of airplanes on the ground.)Ī couple of other answers have hit on the problem here a bit, but the reason isn't that ATC has multiple transmitters and receivers. Short version: Poor quality audio on LiveATC is mostly due to obstructions attenuating the signal. But in general what you hear on LiveATC is much worse than what the controllers are hearing. Of course, sometimes the radio from an aircraft is just terrible thanks to poor equipment or excessive cockpit noise. When I'm flying in these areas, I can hear ATC clear as day but can't make out the aircraft they're talking to because they are hundreds of miles from me, and my aircraft receiver can't see them. Sometimes one ATC frequency covers a massive part of the world. This means that no matter where the aircraft is, it will be within line-of-sight to one of them (except for in remote and oceanic areas, where HF radio or data-link is used).
Therefore, if the person's house cannot see the aircraft (which given the sheer distances involved is common), the audio received will be of poor quality, with lots of static, and sometimes even unreadable.īut real ATC doesn't use just one receiver - there is a whole network of receivers and transmitters, in strategically placed locations. VHF radio waves can only travel in line-of-sight. Aircraft use VHF radio (except in remote and oceanic areas). LiveATC works by an individual volunteering to host a receiver on their house.
The real quality is almost always better, and I'll give a simplified explanation for why.
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