I am a current BC346XT user monitoring Air Traffic Control (ATC) in the Washington DC area. In our area we have Reagan International (DCA), Dulles (IAD), and Marshall Baltimore Washington International (BWI) major airports and several smaller airports.
Some basics may help. Levels of control are provided by Towers (controlling to 5-10 miles from the airport), terminal radar area control facilities (controlling to ~20 miles from the airport) and area control facilities (covering hundreds of square miles).
I have programmed my BC346XT to scan tower, terminal, and area control frequencies. I scan for an local uncontrolled airport (Gaithersburg, MD or GAI) universal communications frequency (UNICOM) and the DCA and IAD tower frequencies. I have also found and programmed some terminal area control frequencies and many area control frequencies. Depending on conditions, I can get some or all of the radio traffic.
For location-based data, we need to understand that towers, terminal control, and area control facilities control different airspace, and their transmitters have different ranges. Also, on the ground you can sometimes receive transmissions from the aircraft but not be able to receive the control facility.
I can receive GAI UNICOM very well. I usually can monitor one sector of terminal radar area control (ground-to-air and air-to-ground). I get many air-to-ground transmissions to terminal and area control sectors but no ground-to-air transmissions. Which a previous thread mentions - air traffic control ground-to-air transmissions are designed to be received in the air. I get few ground-to-air transmissions and usually only from one terminal control sector.
The Radio Reference Guide database does not, I think, have the terminal and area control sector frequencies referenced to a point on the ground. That would help us.
I hope my thread helps. Thanks for reading.