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GPS jamming

Greg Arehart

Greg Arehart

Well Known Member
So, yesterday I flew from RTS (Reno) to ELY (Ely, NV) right across Fallon Naval Air Station, and through the VFR corridor between the multiple Restricted areas. On most days, one can get clearance through the Restricted areas, but not yesterday as they were all hot. So there I am flying carefully in the 1-mile corridor at an appropriate altitude and carefully watching my Garmin 495 so as not to stray into inappropriate airspace. In fact, I was warned by Fallon Desert to be sure to stay N of R4804A twice. Suddenly, the GPS gives me an error that it cannot see the satellites (big question mark on top of my airplane icon on the 495). I had charts, and the corridor is right along an obvious highway, so no big deal there. A couple minutes later, it blinks back on. 5 more minutes and it goes off again, this time for several minutes. I rebooted the GPS and it comes up with "poor satellite reception" but at least I got something. Then it loses satellites for the third time. A few minutes later (distinctly east of any Restricted areas and still in the VFR corridor) it comes back to life.

Initially I was thinking that maybe I had a loose antenna connection or something, but the rest of the way to Ely I had no problems. And no problems on the way home (different route).

This all leaves me wondering if the Navy was using some sort of jamming in/over those restricted areas that screwed up the GPS signals. Anybody else ever have a similar experience elsewhere? I wouldn't doubt that the military has the capability of jamming GPS.

Anyway, it was an interesting experience that also made me realize how easy it is to become dependent on that little TO-FROM line on one's GPS.

greg
 
This happened to me three times in the last two weeks... it does come back up in about 3-4 minutes. I thought my unit was having issues till I tried another one. :confused:
 
You're crusing around some of the "hottest" military airspace in the country. From OT&E, special projects, full blown wargames and live ordinance delivery. One would suspect that during some of these operations, considering that GPS is used on the aircraft and the munitions they are dropping, one could expect some form of ECM "might" be in use to test the skills of the warriors honing their skills or testing their newly issued equipment. ;)

Oh...try the TO/FR flag on your CDI if the GPS give you fits...good practice the old fashioned way :)
 
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Did you check the NOTAMS to see if an outage was posted? It is not uncommon to see GPS inaccuracy predicted around White Sands Missile Range and Holloman AFB in New Mexico - maybe they wee playing games at Fallon as well. It would be highly unusual for them to spoof the signals without posting a NOTAM - there are simply too many airplanes depending on GPS today for unannounced tinkering, and the folks that run the systems are well aware of that.

Paul
 
According to spaceweather.com, there's been an unusually strong solar wind blowing around Earth the past few days and in their words from yesterday's archive, "sparking some of the strongest geomagnetic storms and brightest auroras in years".

I wonder if that might have something to do with spotty GPS reception?
 
I don't know how to search for NOTAM's in the past, but here's one for tomorrow, centered right about where you were:

Oakland Center (Fremont CA) [ZOA]: April NOTAM #31 issued by Gps Notam OA [GPS]
Navigation GPS is unreliable and May BE unavailable WITHIN A 375 nautical miles RADIUS of 393101N/1175659W LOVELOCK / LLC / VORTAC 141.25 DEGREE radial at 46.65 nautical miles, at FL400; decreasing in area with DECREASE in altitude to 290 nautical miles RADIUS at FL250; 220 nautical miles RADIUS at 10000 ft. mean sea level, and 220 nautical miles RADIUS at 4000 ft. above ground level. effective from April 09th, 2010 at 06:00 AM PST (1004091400) - April 09th, 2010 at 11:30 AM PST (1004091930)

--Paul
 
A familiar occurrence for New Mexico pilots

This sort of thing has been going on around Hollowman/White Sands for at least four years. It is easy to become complacent , but there really is wisdom in checking NoTAMs along the route.
 
Rick S. said:
Oh...try the TO/FR flag on your CDI if the GPS give you fits...good practice the old fashioned way :)
Click to expand...

Yesterday, I read that the FAA has began the decommisioning of a few VORs. It was in a magazine, and therefor, the article could already be a few months old by print time. If that's the case, the VOR might already be gone.... :D

L.Adamson --- RV6A
 
Travis AFB

I lose GPS reception over Travis AFB in N. California about 1 out of every three trips at 8500' to 9500'. It is an active base but I would not call it a "hot" area and there is a lot of GA traffic. I lose it on my 296 for a couple of minutes and then it returns. I have fired up my backup 96 with the same results. I asked Travis Approach once (I was on VFR flight following) and they said there was no problem to their knowledge. I have gotten used to it but it does sound similar to some of the other postings here.
 
It's called "selective availability". It's the primary reason the EU is building Galileo. It's also the reason why I think decommissioning the VOR system in the US would be a big mistake. Yeah, maybe we don't need quite as many VORs, but having a backup to GPS is great. As has already been mentioned, solar storms can wreak havoc on satellite based systems.
 
It's called "selective availability".
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SA is something different, which just reduces accuracy and which hasn't been used for years. This is GPS jamming. See http://www.navcen.uscg.gov/gps/gpsnotices/default.htm

Here is a PDF listing GPS interference test sites for 2010: http://www.navcen.uscg.gov/gps/gpsnotices/GPS_Interference.pdf. It includes the White Sands site that Paul and Louise mentioned, the China Lake site that shows up in SoCal NOTAMs all the time, and one at Church Hill NV which corresponds to the Fallon NAS location that Greg saw.

--Paul
 
Rick S. said:
... One would suspect that during some of these operations, considering that GPS is used on the aircraft and the munitions they are dropping, one could expect some form of ECM "might" be in use to test the skills of the warriors honing their skills or testing their newly issued equipment. ;)
...)
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This makes me wonder what it would do to my electronic ignition. Are they strong enough to turn me into a glider?

BTW, this will not be just an E/P-mag problem but a problem all EI's would/could run into.
 
N941WR said:
This makes me wonder what it would do to my electronic ignition. QUOTE]

I know they do some static EMP testing on equipment/vehicles/aircraft at Kirkland AFB in NM, I would assume that any tactical tests of EMP would be very limited in the area of civilian operations. The collateral damage would be dangerous and expensive. But who knows:eek:
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Pretty common in the corporate jet I fly too, since most of my flying is in the Western U.S. around the military areas. Notams usually cover them. If my FMS loses gps signal over these and stays off for a bit, I notify ATC and ask them to check my heading and they usually just give me one.
 
The fact (from the NOTAM) that the area of unreliability increases with altitude
suggests this is a ground based signal derogating the GPS function. Do others with more knowledge agree? I suppose satellites could be programmed to make signal bad in certain areas, but uninformed common sense would seem to indicate a constant or increasing area of disruption at lower altitudes if this were the case. Changing WAAS wouldn't seem to cause the problems you described. Hope somebody on the forums knows how to explain this precisely.
 
For a determined entity...

...it is not difficult to "jam" a localized area of GPS reception.

Remember, each GPS satellite transmits signals (timing/ranging /sat nav data) on two different carrier frequencies. This information is received by the GPS receiver in our aircraft (car, boat, etc). This timing info is decoded by the GPS receiver's processor and applied to a "map" that may be a part of the particular GPS display screen software and current data base.

GPS position accuracy is adversely affected by a number of variables (satellite celestial position, atmospheric, sun spots, noise, etc). A good GPS receiver will constantly monitor the signal quality of the received signal based on the expected signal characteristics, as each variable will introduce a specific type of signal error.

A sophisticated GPS jam activity would broadcast a signal that would affect a group of targeted receivers and cause them to believe the received signal was degraded to the point of not being reliable. This mimic signal would fall into the group of expected variables as described above.

A bruit force approach would be to use a high power transmitter, tuned to one or both of the satellite down link carrier frequencies, and just clobber the local GPS receivers with a jamming signal. The local GPS receivers would not be able to recover the real GPS sat signal, so "GPS Unavailable" would result.

It is easier to confuse the local receiver with the brute force approach than to target a constantly changing number of locally visible GPS satellites, moving across the sky.
 
You need to buy a few more letters...

Jamie said:
It's called "selective availability". It's the primary reason the EU is building Galileo. It's also the reason why I think decommissioning the VOR system in the US would be a big mistake. Yeah, maybe we don't need quite as many VORs, but having a backup to GPS is great. As has already been mentioned, solar storms can wreak havoc on satellite based systems.
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It's probably not Selective Ability (SA)

More likely testing of SAASM --

http://en.wikipedia.org/wiki/SAASM

...which is built-in to almost all military GPS equipment.

When I worked at Raytheon, engineers would go to Sierra Vista/Fort Huachuca to test missile GPS jam-resistance...:)
 
Huh...

july77 said:
Yeah, I fly in England and I get a lot of jamming on my gps. Thumbs up for the Galileo and a gps europe!
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Your link goes to GPS products made in Europe (but probably China...:)...) that use the US GPS system, at least on the lower cost products.

The Navman M300 - highlighted on the home page - uses this GPS reciever module...

http://en.wikipedia.org/wiki/SiRFstar_III

Nothing to do with Galileo as far as I can tell...:rolleyes:
 
While it may be related to military activity, it may not. I had the same thing happen to me as I flew around Chicago last fall. GPS (396) lost satellite reception THREE times. I tried rebooting, etc., and after a few minutes it got signals again. I also thought it was a bad antenna connection or something, but it happened AGAIN on the reverse course. Same area SW of Chicago's Mode C veil. There are no military operations close to that area, and it's a pretty congested area considering the proximity of ORD and MDW, let alone a bunch of small GA airports.
 
Just a couple of points to clarify others made here...

Firstly, our common GPS receivers are only using the single L1 carrier frequency of 1575.42MHz. This carrier is encoded with what is known as C/A code or SPS (standard positioning service) data. L2 is pretty much restricted to military use, so our Garmin's, AvMaps etc don't have access to it. The data rate on L2 is 10x that of the data on L1, contributing to better potential position accuracy, hence it's known as PPS or precise positioning service. The differences in propagation delay between L1 and L2 carriers allows military GPS receivers to calibrate many ionospheric effects, again leading to more precise positioning capability.

Secondly, the GPS signal is very small indeed. It doesn't take very much transmitted power from an interference source to take GPS off line. In the early days of GPS development (my employer made the first standalone C/A code GPS receiver with full ARINC autopilot interface) I could use a signal generator and an omnidirectional antenna, without an amplifier, to take GPS offline from a range of about 1/4 mile. A ground-based GPS jammer can be just a very simple CW transmitter - that's all that's needed to wipe out the GPS signal by brute force. Of course it also doesn't take very long to use basic homing techniques to find that jammer and, ah, "eliminate" it... ;-)
 
Just stumbled across this thread.

Greg, if you want to know what was going on, we'll meet up. I can tell you in UNCLAS terms why you PROOOOBABLY don't want to be cruising that corridor when things are "hot." And yes, your outage was directly related things going on around you.
 
Magenta Line Inop Procedures

lucky said:
http://www.computerworld.com/s/article/77702/Homemade_GPS_jammers_raise_concerns

http://www.avweb.com/news/avionics/182754-1.html
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Lucky,

A quote taken from your Av Web link above:

"Plan Ahead
What can you do to protect yourself? IFR pilots should have a fallback plan in case of a GPS malfunction: Have an alternate airport with something other than a GPS approach, and an alternate flight plan using other navigation means (such as VOR-DME navigation along published airways) in case GPS becomes unavailable for direct-to navigation. VFR pilots should always cross-check their position using visual references on a sectional chart or ground-based navaids.":)

Thanks for the link.

Regards,
 
Originally Posted by lucky
http://www.computerworld.com/s/artic...raise_concerns

http://www.avweb.com/news/avionics/182754-1.html

Lucky,

A quote taken from your Av Web link above:

"Plan Ahead
What can you do to protect yourself? IFR pilots should have a fallback plan in case of a GPS malfunction: Have an alternate airport with something other than a GPS approach, and an alternate flight plan using other navigation means (such as VOR-DME navigation along published airways) in case GPS becomes unavailable for direct-to navigation. VFR pilots should always cross-check their position using visual references on a sectional chart or ground-based navaids."

Thanks for the link.
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Since we're looking at these links again, I want to remind everyone, that they are from 2003. How many serious cases of jamming have we had since then? How about the two solar storms last summer. Doesn't look like GPS was effected. Overall, it appears that GPS has been quite dependable......at least in the US with WAAS. Going back to the year,2004, I recently read a thread in a student pilot forum, in which a CFII was so into the VOR/NAV system, that he continually called GPS a "toy". I hope he's changed his mind in the last six years...

Regardless, for IFR we'll have VOR as a backup (at least for a period of time), though possibly not DME. And yes, position awareness is very important for VFR. Don't just lazily follow the magenta line.......especially when there are "red" splotches ahead!

L.Adamson ---- RV6A, Garmin 696
 
L.Adamson said:
Regardless, for IFR we'll have VOR as a backup (at least for a period of time), though possibly not DME.
Click to expand...

You would have to look at the Federal Radionavigation Plan to know the current plan for ground-based navaids.

However, I would expect that DME stays since that is more useful to commercial aircraft.
 
jferraro17 said:
Old thread, new article. Just throwing it out there...

http://www.gpsworld.com/gnss-system/news/data-shows-disastrous-gps-jamming-fcc-approved-broadcaster-11029?utm_source=GPS&utm_medium=email&utm_campaign=Navigate_01_31_2011&utm_content=data-shows-disastrous-gps-jamming-fcc-approved-broadcaster-11029
Joe
Click to expand...


That's a very alarming article, especially the parts about the performance degradation of aviation GPS units in the presence of the ground-based transmitters. (For those who haven't read the article, it says that the FCC has approved a company called LightSquared to install up to 40,000 high-power, ground-based broadband transmitters in the US, each of which will begin to jam an aviation receiver at 13.8 miles, and will effectively shut down GPS reception within 5.6 miles of each transmitter. These numbers were for a Garmin GNS 430W. In testing, the automotive Nuvi design did a little better.)

The FCC's Chief of the International Bureau, Mindel De La Torre, was not swayed by the protests of the GPS manufacturers; perhaps she would be influenced by a whole bunch of respectful, concerned pilots who wrote to her at [email protected], or called her at 202-418-0437.

In addition, you might also contact some of the lawmakers who are responsible for this issue. All the contact information is in this article.

.
 
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Buck,

Not sure how you guys do things at work, but we have put a lot of emphasis on GPS approaches the last few years of recurrent. Preparing for the future and all that. This article sure raises a lot of questions (and Captain's eyebrows :eek:)

J
 
By my math, with a 5nm radius of black out that's 3.13 million square miles of complete loss of service.

The US (according to Wiki) is only 3.79 million square miles.....
 
Sig600 said:
Just stumbled across this thread.

Greg, if you want to know what was going on, we'll meet up. I can tell you in UNCLAS terms why you PROOOOBABLY don't want to be cruising that corridor when things are "hot." And yes, your outage was directly related things going on around you.
Click to expand...

If its UNCLASSIFIED, why not tell us all?
 
Sig600 said:
Do you really care about the deails of the land marks and specific operating areas that are local to just us?
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I'm wondering how all of this will play out. Here is an article, and a quote from it, regarding Lightsquared, and their 40,000 potential towers. As I'm a real fan of GPS & synthetic vision..............I don't want to see any problem stand in the way.

http://blog.connectedplanetonline.c...quared-faces-roadblock-over-gps-interference/


While dealing with regulators, LightSquared may also be facing challenges from its investors. LightSquared?s primary investor, the Hedge Fund Harbinger Capital, has recently seen a spate of staff departures and a shrinking of capital as nervous investors withdraw their funds, according to Reuters. Harbinger has so much of its capital tied up in LightSquared?an estimated 40%?that Harbinger is being forced to liquidate its other holdings to cover the withdrawing stakeholders. LightSquared?s initial launch of 20 markets in 2012 is already funded, and it has already launched its first satellite, but it will need to go back to Harbinger or other investors to get funds for the rest of its build out.

L.Adamson --- RV6A
 
From AOPA article...

FCC: Bandwidth expansion must not interfere with GPS
Network operator must work with users on assurances
By Dan Namowitz

A communications network operator whose plan to expand its use of the radio spectrum triggered concerns about interference with GPS signals must not proceed until it assures GPS users and regulators that no conflict exists.

The Federal Communications Commission (FCC) issued an order Jan. 26 imposing compliance requirements on mobile-satellite services network operator LightSquared as a condition of authorizing its use of bandwidth close to the frequencies used for GPS.
AOPA requested assurances from the FCC in a Jan. 14 letter from Senior Vice President of Government Affairs Melissa Rudinger that potential threats to general aviation?s extensive use of GPS be thoroughly investigated before authorization is granted. GPS forms the backbone of the FAA?s Next Generation Air Transportation System (NextGen). The FAA has also expressed concerns about potential signal interference.

...there's more on AOPA site.
 
Air Force Update on Testing

I saw this in my morning AF Association update: "Empirical Backs Up the Analytical: Data from testing actual hardware appear to confirm initial concerns that a new 4G wireless broadband network in the United States would interfere with the Global Positioning Satellite signal, said Gen. William Shelton, head of Air Force Space Command. "Although the data [are] still being analyzed, I would tell you that the empirical data [appear] to be consistent with the analytical data," Shelton told the Senate Armed Services Committee's strategic forces panel last week. Accordingly, he continued, "we have concerns" for civil, commercial, and military applications involving GPS. LightSquared, a telecommunications company headquartered in Reston, Va., seeks Federal Communication Commission approval to establish the broadband network, which would feature thousands of cell phone towers and space-based augmentation. Those towers could disrupt the GPS signal, and testing of LightSquared equipment at Kirtland AFB, N.M., with various GPS receivers seems to confirm that, said Shelton during the May 11 hearing."
 
notam for gps testing near Las Vegas

There is a notam for intermit GPS outages 500 nm rad around LV through July 23. Yes 500 nm! the map included has the rings which depict area which increases with alt. I dont know what the testing is about, but I suspect it has to do with the Lightsquared issue. There has been a succession of similar notams recently.
 
Watched an interview of Lightsquareds Sanjay Ahuja on CSPAN last night.

Obviously a smart guy with good intentions to provide communications to every hovel in the US, ....and make a lot of money for his investors.

Basic defense of GPS interferance is that the affected receivers are cr@p and should be fixed by the OEMs......right. I expect my new 430W (one of the test failures) to be replaced with a new one by Garmin free of charge. Not.

He has offered X dollars to address the government units (defense etc) so I assume us civilians are hung out to dry.

This system has been in the works for quite some time, with regulatory action from 2003 and 2005 approving the frequency use at very low power levels for satelite uplink/downlink. This was probably A-OK from a technical sense and got all positive nods. (This is the basis for Ahujas defense "that the freq use was known and approved by everybody for a long time"). The change (as I understand it) is a recent need/desire to vastly increase the transmitting power and quantity of ground stations which will overwhelm the "non-descriminating" aviation receivers. I get the destinct impression that there is $$ and politics in the recent change. I think that's the basis of the fight on the hill.

I hope and pray that the RIGHT decisions will be made in DC. I can't imagine somebody ignoring the safety aspects of navigation loss in the coming primary GPS IFR environment.

Sorry if this is too close to the rules edge. I'm upset about it and feel powerless. Delete if its deemed over the top.
 
Interesting article...looks like LS may have some bigger issues now. It's hard not to sound political talking about the 2012 Defense Authorization Act, but I'm really only trying to point out the LightSquared part of this:

A clause buried deep in the 565 pages of the 2012 Defense Authorization act passed in December bars the Federal Communications Commission from approving systems that interfere in any way with military GPS. The bill also tells the FCC to supply Congress with a final copy of the report from its working group, which late last year issued a preliminary report warning that a system proposed by telecoms firm LightSquared of Reston, Virginia would cause serious interference.
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http://www.newscientist.com/blogs/onepercent/2012/01/new-act-scuppers-lightsquareds.html

...granted it also says "military GPS".. I haven't dug to find the actual text in the bill.
 
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Maybe it's this (p. 237):

Subtitle B?Space Activities
SEC. 911. HARMFUL INTERFERENCE TO DEPARTMENT OF DEFENSE
GLOBAL POSITIONING SYSTEM.
(a) FEDERAL COMMUNICATIONS COMMISSION CONDITIONS ON
COMMERCIAL TERRESTRIAL OPERATIONS.?
(1) CONTINUATION OF CONDITIONS UNTIL INTERFERENCE
ADDRESSED.?The Federal Communications Commission shall
not lift the conditions imposed on commercial terrestrial operations
in the Order and Authorization adopted on January
26, 2011 (DA 11?133), or otherwise permit such operations,
until the Commission has resolved concerns of widespread
harmful interference by such commercial terrestrial operations
to covered GPS devices.
Click to expand...
There was another similar mention too.

I think Lightsquared is dead.
 
my understanding

It is my understanding that the "save our GPS Coalation" has got some suppport on the hill and was able to introduce this language to keep lightsquared at bay. I also understand the FCC rules are that new users must accomadate "old" or heritage users. If I remember right, Lightsquared is trying to use a frequency band originally assigned for satellite communication, in a terrestrial application. Not good.
 
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