Nope, GPS for aviation is essentially one frequency with code modulation. The
receiver picks out the different satellites by correlating the code sequence
against the received signal. The code sequences are orthagonal, which means they
are enough different that you only get a strong correlation peak for the one
satellite that matches the code you are correlating against. The long code
sequences provide a very high processing gain, so the signals can be buried in a
good deal of noise, however it is relatively easy to jam the entire system with a
strong transmittter on the carrier frequency. This is what RAIM is all about. It
doesn't even have to be an intentional jammer: intermodulation from TV transmitters
in close proximity has caused local outages, for example.

It would be much harder to jam the entire VOR band because the VOR signals are
transmitted at much higher power (3 orders of magnitude), and the VOR band covers a
wide frequency band relative to the frequency of the center of the band.

Scott Moore wrote:

C J Campbell wrote:

Bull****. GPS also works using multiple satellites and multiple frequencies.
If you are going to propose that the entire frequency band for GPS be jammed
or otherwise corrupted, then the same thing would work across the entire
VOR band as well.

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--Ray Andraka, P.E.
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401/884-7930 Fax 401/884-7950
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