Depends on what you are listening to. Because aviation band is VHF, you receive in line-of-sight. YOu can listen to the aircraft calling the ATC centers but you can't hear the controllers reply unless you are fairly close to the center. You may be able to pick up the control tower from a few miles away but, again, it depends on line-of-site. I can listen to the Hayward tower even though I live a few miles away from it but because I live on a hill, I have a line of sight to it. David R > how close do I have to be?