ADS-B to FR24
My ADS-B receiver was provided by FR24 and it has both an ADS-B antenna and a separate apparently amplified GPS antenna. My assumption is that the reports that go out are time stamped with time of reception using very accurate time from GPS. I'm located in a very desolate area in Nevada near Death Valley and get quite a few lower level flights that are missed by some FAA resources. And often see aircraft ADS-B signals about 30 miles out over the Pacific near San Francisco and well into Utah.