Big News -- WAAS GPS is Operational for IFR

"Bob Noel" wrote in message
...
In article , Scott Moore
wrote:

I never claimed that GPS was immune to jamming. I have stated, and I
stand
by it, that it is pointless to argue about GPS jamming if the other,
existing services can also be jammed.

Then we'll just have to disagree. I'll stand by the fact that
GPS jamming can be achieved with much lower transmitted power
than for any of the other existing radio navaids. This is the relevant
point.

In what way is your point relevent, Bob? It seems to me that spoofing is
far more an issue in creating an intentional navigation hazard.

But since nobody here has ever produced proof of either

what? you've never seen any proof that GPS can jammed and
quite easily?

Why do you think that certain transmitted VHF frequencies
have to be checked during a GPS installation?

Harmonics from your Com radio.

Is there anything on your aircraft that can jam any other existing
radio navaid?

Sure.

John P. Tarver, MS/PE

"Richard Kaplan" wrote in message
news:12314a1ab0a0c5f1420eacc57b51be6d@TeraNews...
|
|
|
| "C J Campbell" wrote in message
| ...
|
| It would be interesting to see some data that show that GPS is
frequently
| compromised by unintentional jamming. If someone says that GPS jamming
is
| a
| problem, the burden of proof is on them to support that assertion.
|
| Intentional or not, there are frequent NOTAMs that GPS is unreliable in
| certain regions. Who knows if this is due to technical issues or military
| testing or whatever. No matter the cause, it is clear GPS can and will
| become inoperative at certain times in certain regions. It therefore
seems
| rational to expect that non-GPS backup nav system will need to remain in
| place indefinitely.


I might point out that VORs are also inoperative at certain time in certain
regions. The Mc Chord VOR has not worked in over a year, despite it being an
important airway intersection. So what are you suggesting we use for backup
navigation systems for the VOR?

"C J Campbell" writes:

I might point out that VORs are also inoperative at certain time in
certain regions. The Mc Chord VOR has not worked in over a year,
despite it being an important airway intersection. So what are you
suggesting we use for backup navigation systems for the VOR?

Redundancy. In the continental U.S., you have an extremely dense VOR
system, so that you will usually be in reception range of quite a
few other VORs and can easily navigate even without radar vectors; in
Canada, we have a parallel system of NDB airways to accomplish
basically the same thing.

If Galileo ever gets running, you can have that kind of redundancy for
satellite-based navigation as well.


All the best,


David

--
David Megginson, , http://www.megginson.com/

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:

I might point out that VORs are also inoperative at certain time in certain
regions. The Mc Chord VOR has not worked in over a year, despite it being an
important airway intersection. So what are you suggesting we use for backup
navigation systems for the VOR?

--
--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

Bob Noel wrote:

In article , Scott Moore
wrote:

I never claimed that GPS was immune to jamming. I have stated, and I stand
by it, that it is pointless to argue about GPS jamming if the other,
existing services can also be jammed.

Then we'll just have to disagree. I'll stand by the fact that
GPS jamming can be achieved with much lower transmitted power
than for any of the other existing radio navaids. This is the relevant
point.

Well I sure feel safer knowing that Everready access stands in the way of the
terrorists !


But since nobody here has ever produced proof of either

what? you've never seen any proof that GPS can jammed and
quite easily?

Why do you think that certain transmitted VHF frequencies
have to be checked during a GPS installation?

What we have seen is lots of folks who like to make headlines, and very
little in the way of actual studies, including comparitive studies on
jamming GPS vs. jamming other services.

Again, again, and again as many times as you want to go around this
tree, if VOR can be jammed just as well as GPS, there is no reason
for chicken little to run around yelling about the vulnerability
of GPS. It makes no sense to claim that VOR is "better" based on
one sided distorted comparisions, which ignoring *any* ability to
jam VOR certainly is. I don't care if it costs $1000 to build a VOR
jammer vs. $100 for a GPS jammer. The fact that both can be jammed
is a relivant point, unless you are going to now argue that lack
of $900 can keep all these imagined terrorists ready to attack the
GPS system at bay.


Is there anything on your aircraft that can jam any other existing
radio navaid?

Whatever. We are back to mudslinging and lack of facts. I don't have
the ability to evaluate GPS jamming, nor VOR jamming, and you basically
have the ability to yell a lot. Neither is productive, but at least I am
honest about it.


--
Bob Noel

--
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.....

David Megginson wrote:

If Galileo ever gets running, you can have that kind of redundancy for
satellite-based navigation as well.

All the best,

David

There are multiple GPS satellites making up the GPS system. That is the
exact same redundancy.

--
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.....

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.

Scott Moore writes:

If Galileo ever gets running, you can have that kind of redundancy for
satellite-based navigation as well.

There are multiple GPS satellites making up the GPS system. That is the
exact same redundancy.

Not quite, or we would never get RAIM problems.


All the best,


David

--
David Megginson, , http://www.megginson.com/

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