Nah - you're specifically using technology that allows you to set any frequency you want, but instead, you're picking the frequency that is illegal for you to listen to and then you're recording it.

Moreover - when you finally get caught, on which scale do you have to be doing it to get caught in the first place? Remember - laws don't exist outside reality.

And let's be honest - the recording of the presence of a car is also quite illegal in certain jurisdictions. e.g. Germany.