Scott Moore wrote:
"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 ?

Existing receivers will not support the new frequencies and I doubt
there'll be an option to retrofit them. No worries though, all birds
will continue to be backwards compatible.

2007 is only a target date for the first bird to be launched. You won't
see enough birds up there (18 is typically the minimum to ensure enough
birds are in view at any time from any location) to support the
availability requirements that aviation has. Don't expect to have to
consider upgrading to an L5-compatible receiver until at least 201x

The new civil signal on the IIFs is L5 while the IIR-M birds will offer
L2C. From http://pnt.gov/FRP2001.pdf:

"The U.S. Government has determined that two additional coded signals
are
essential for certain uses of GPS. A second civil signal will be added
at the
GPS L2 Frequency (1227.60 MHz). A third civil signal that can meet the
needs of
critical safety-of-life applications such as civil aviation will be
added at
1176.45 MHz. The third civil signal frequency is designated as L5."

Regards,
Jon