Hello Dushan,
thanks a lot for the answer!
The unit I have is the IC-A24. I live in an appartment complex and I am located 16km from the airport. I can hear very clearly from the inside of my appartment almost all the frequencies (only aeronautics frequencies), from the ramp to the ground, tower, dep, app, center.
I'm surprised that it is useless inside the aircraft? i thought it was going to be crystal clear. I'll try it and give you a feedback (my flight is the 4th of May).