My guess is as follows. If the testing is on FDNY CW2 486.38125, these are both within TV RF CH 16 & 17 bandwidth . The input is likely 489.38125 TV17.
While I have not logged TV16 yet, I have logged RF TV 17 television stations. Philadelphia and Vineland New Jersey.
Band openings known as tropo can raise the noise floor when the openings occur.
I get TV 17 every day, even without band openings.
I suspect they are looking at this.