Unfortunately there's intruders in the ham bands all the time. Crane operators, glider and tow plane pilots, plumbers, dog hunters ( if they aren't using marine radios...) and so forth and so on. Back in the day, once you tracked them down and could identify where they were and when they operated you could make a phone call to the FCC field office in Tampa and talk to Ralph Barlow and give him a heads up. They'd send a guy out to the location and he'd listen for a while and make some recordings and then they would send in an FCC investigator along with a Federal LEO and shut them down and sometimes even seize their equipment. Early 1980s there was a high rise hotel being built and everybody on the job site was parked on 144.200 FM. Didn't take too long for them to get shut down, I heard there was multiple cases of Icom 2 AT radios that were seized and the GC running the job got fined pretty heavily. It has only gotten worse with the advent of less than $50 Chi-Com radios being available on Amazon and eBay that work in the ham bands that anyone can buy and lack of manpower or general caring from the FCC to enforce anything.
Now that that rant is off, there could be something technical as well depending on the radio receiver you're using. Program up 452.325 and 463.025 and see if you can hear them there. If so they would probably be much stronger. Depending on the type of receiver you have you could be hearing an image based on the IF frequency of the radio receiver usually 10.7 or 21.4 Mhz. Since you say you're located in the Tampa Bay area, there's a much better chance that they're located near you and you're hearing an image as opposed to them being directly on the 441 frequency a long ways away but it really could be either. 5 Watts goes a long way when you're 500 ft in the air.
