I did raise eyebrows once of the person in the row behind me. I said I was listening to ATC and that seemed to placate him. I do believe most airlines have a blanket ban on radio equipment, even receive only. Some even ban using GPS!
Many, many, many years ago (before 9/11 and before cell phones were commonplace) I used to carry my ham radio HT and call on simplex (146.52 for those that know) and make contacts. Those were fun times.