"While the new series has just begun to fly, the Air Force has the next generation
already in the works. The GPS 2F satellites are under construction at a Boeing plant
in California. They will feature the original and the new modernized signals, plus
offer a third civilian signal of particular interest to the aviation industry. A
dozen of those satellites will be built, with the first launch anticipated in 2007
from the Cape."

What are they talking about ? Do recievers need to be changed to obtain the
better accuracy of the new satellites ?