Big News -- WAAS GPS is Operational for IFR

Ray Andraka wrote:

The difference is that a VOR outage affects only that VOR, so a workaround
exists using other VORs and the same equipment in the aircraft. A GPS outage
affects the system, at least within an area, so there are no alternative
stations to tune to for a work-around.

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.

--
For most men, true happiness can only be achieved with a woman.
Also for most men, true happiness can only be achieved without a woman.
Sharp minds have noted that these two rules tend to conflict.....

"Scott Moore" wrote in message ...

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.
Umm, no. GPS, as far as aviation is currently concerned, operates on a single
frequency called L1 (1.57542 GHz). Even if you were to use L2 as well, they aren't redundant.
The reason for the second frequency (civil use) is to allow correction to the ionospheric
propagation delay.

In theory, the spread spectrum nature makes it difficult to jam effetively. Of course, that's
with an ideal reciever. You can knock out a lot of receivers by just throwing enough RF
at them.

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.

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

Please do not mis-attribute others' remarks to me. I did not post the quoted
material.

"Ray Andraka" wrote in message
...
| 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.
|
| --
| --Ray Andraka, P.E.
| President, the Andraka Consulting Group, Inc.
| 401/884-7930 Fax 401/884-7950
| email
| http://www.andraka.com
|
| "They that give up essential liberty to obtain a little
| temporary safety deserve neither liberty nor safety."
| -Benjamin Franklin, 1759
|
|