Daysleeper,
Yes a Personal radio can have that effect, and I presume so could some of the wiggly amp thingies on a flight deck. However that breath test is only a screening test, certainly in the UK, and gives reasonable grounds to suspect that someone has a blood alchol limit above the prescribed limit.
In the UK you would be arrested (which is not saying you are guilty) and taken to a Police Station. There you would take a further breath test on a calibrated machine which gives a print out admissable in court. That is then the evidence of having the blood alcohol concerntration above the prescribed limit. In other words even if something does interfere with the initial screening test it would not lead to an appearence before the magistrates for nothing.