When I have traveled by air in the past with electronics, usually handheld scanners and ham radios, I have not experienced any major problems with my carry-on bag containing them along with accessories such as programming cables, small battery chargers, AA batteries packed in very small designed cases, and other related items. I did take several steps in case I was asked to turn on any of the radios which never happened.
I programmed each radio to immediately receive NOAA weather radio when turned on, rather than receive police or other public safety radio transmissions which might lead to other questioning as to why I listened. When a ham radio was in the case I kept a copy of my FCC license in plain view which anyone opening the case would immediately see. If I had to explain ham radio I kept a recent copy of QST magazine sitting in the outside pocket of the carry-on bag. The only time the case was opened by personnel at the security checkpoint was after it passed thru the x-ray machine as many cables and other odd appearing objects appeared on the x-ray monitor. It was understandable that they needed to examine the bag's contents.
The funniest experiences I had while traveling happened back between 1979 and 1980 with a mobile/base scanner in the briefcase along with a built-in battery pack consisting of "D" cell batteries in plain view once the case was opened. It went thru the x-ray machine and the private security agent at the checkpoint said she needed to open it. She did and did not have a clue as to what she was looking at. I explained it to her, but she wanted airport police to look at it. An officer arrived with in minute or two and told her, "these are just batteries". Neither of them were concerned about the radio. This was in the Tampa, Florida airport.
The next experience happened in Dallas in 1980 I think. It was the same radio I mentioned above, a Bearcat 250 base/mobile scanner with the battery pack that I had built for it. Back then the carry-on bags were examined at a checkpoint next to each gate, rather than at a concourse entry point. The briefcase went thru the x-ray machine and the female security agent said, "I need to open it" and she did. When she opened it she looked at the radio for about one second and then looked at my law enforcement ID that I had clipped on to the inside of the case making it easily visible to her. She then looked at me and said, "That's all I need to see". She closed the bag and I walked aboard the aircraft.
On a few occasions when I was sitting in the boarding gate area waiting to board my flight with a lot of time before departure, I would sometimes listen to my handheld scanner using a set of ear buds with the radio sitting inside the bag so it could not be easily seen by others.
I never had had a problem with this.
As to the briefcase with the base/mobile radio in it, I also had installed an earphone jack on the outside of the case, near the handle in 1977 so that I could walk around with the case and listen to it via an earphone. The case also had a built-in wire antenna for receiving the transmissions. This was before programmable handheld scanners were readily available.
How radios and monitoring habits have changed.
