wrote:

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."

Interesting... does this herald a return to some kind of Selective
Availability so that Unky Sam can shut down access by non-critical
receivers? If not, what is the purpose of a third signal, is it just
for redundancy?

-cwk.