[oigftrgtyh]

Has the FCC ever bothered to actually go after people that abuse bits of the spectrum? Wardrobe malfunctions they are right on top of - but anything that requires technical knowledge seems to escape them.

GPS does have a group that protects it's users - I believe it's called the USAF.

[jws]

A few years ago the FCC showed up at a coworker's house with their van. Something in his house was emitting improperly. They eventually tracked it down to a computer monitor.

So there are enforcement people out there. They just don't happen in the middle of a superbowl broadcast.

[Kadin]

Yes, the FCC has an enforcement bureau (http://www.fcc.gov/eb/).

They unfortunately do not have nearly enough officers to really do anything particularly effective, but if you are really egregiously bad about your spectrum abuse, to the point where you generate complaints from other users, they do sometimes pull licenses.

The only interaction with them I have any sort of knowledge of is secondhand; a friend of mine spent months trying to get the local power company to fix a bad transformer on the street that was failing internally and creating a lot of noise, pretty much from DC well up into the HF. (And I suspect it was making some pretty ugly AC waveforms.) They wouldn't do anything, and he eventually got one of the FCC Enforcement Bureau people involved.

You have to be a very "squeaky wheel" to get any sort of attention to a complaint, though; my friend had what amounted to a fairly serious engineering study of the failing transformer, done with parabolic antennas and spectrum analyzers, so that the FCC guy didn't really have to do a whole lot. (Presumably he verified things, but I don't know for sure.)

[trafficlight]

A few years back, a local WISP (in Montana) was shutdown because they were breaking the Part 15 power rule in several markets. Their custom made radios were putting out over 5 watts EIRP, when the maximum legal limit is 1 watt. It took the FCC several years to get out here, but they did do it.

[kpeel]

Funny enough, if GPS does get jammed, the USAF has a whole lot of equipment that would be almost useless... Like every modern airplane they own.

[oomkiller]

Actually most modern munitions are guided by inertial navigation, mainly so targets can't jam them. Aircraft etc also have this capability. They have known about the risk of jamming since the beginning, so surely they've prepared for it.

[kpeel]

Very true. My answer was a bit tounge-in-cheek, I just didn't get it across properly. While losing GPS would be a problem, it certainly wouldn't bring down our military.

This specific problem definitely wouldn't affect our aircraft simply because they would be at such a high altitude. Even if it was a problem, the military also has a some pretty impressive anti-jamming capability.

[smallblacksun]

Conveniently, the USAF also has a lot of anti-radiation missiles that are very good at eliminating jamming sources.

[mkr-hn]

We need someone with air force experience in here. It doesn't seem like they'd let them fly without knowing alternate ways of navigating.

[caf]

US Military GPS has access to a separate P(Y) signal on the L2 frequency that civilian GPS does not.

[winthrowe]

I'm not actually air force, but am a bit of an aviation buff with a private license. There would be backup nav systems in manned aircraft, but several popular modern munitions are GPS guided, and I would tend to think that modern battlespace information systems require it as well. Planes wouldn't fall out of the sky, but it would be a significant departure from the ideal state.

[mkr-hn]

If you have time, I wouldn't mind some examples. I'm curious, not doubtful.

Since this thread sprung up I've wondered what might be impacted by a GPS failure.

[winthrowe]

Of the munitions? I hear JSOWs and especially JDAMs are popular recently.

As far as BIS info, it's not something I've followed closely, but we're talking things like every plane, tank, and infantryman now (soon?) has gps and information on the location of all friendly forces is automatically shared so you cut down friendly fire.

Apparently caf has more info on milspec GPS than I do, I thought that it required the same main band as civilian, and just used additional military bands to increase precision, but apparently it can function fully independently (not really surprising when you think about it). At least that gives you a little info on some of the troubles of failure of military GPS, as unlikely as that is.

http://en.wikipedia.org/wiki/Joint_Stand-Off_Weapon

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

[oigftrgtyh]

Descend until you can see the freeway and follow that is always popular!

[mkr-hn]

It's obvious now that I think about it. Even with GPS, they're going to be told landmarks and indicators (roads and stuff) during a briefing.

[aj700]

Why shouldn't this break military plane GPS as much as anything else. It will also remove the ability of USAF to GPS target missiles onto US population centres, which they have no need to do anyway. They can still bomb the rest of the world no problem.

[Kadin]

Military GPS receivers operate on two carrier frequencies, only one of which is used by most civilian models. (And it's the shared military/civilian frequency which is adjacent to the spectrum in question.)

Using two frequencies makes the military receivers more robust, and also lets them do some clever ionospheric distortion cancellation that you can't do with one channel. (Basically they get the benefits of WAAS without actually needing to receive the WAAS signal.)

That said, neither the FAA or the military are going to tolerate any significant degradation of GPS, domestically or otherwise.

[kpeel]

Yeah, I was joking a little. Most aircraft would still work pretty well off of inertial data. However there are quite a few weapons systems that just plain won't work without GPS.

BTW, I'm not a pilot, but I work for a government aerospace contractor, so I have some experience in this.

[icegreentea]

I thought the most common ones (JDAMs) still had an inertial navigation system cause GPS/INS is used nearly everywhere. It'll probably have horrible accuracy (I guess that depends on how the coordinates sent to the bomb are handled... if it can be calculated as an offset of what the INS thinks it is, then it wouldn't be that bad). But still better then unguided bombs.

[mkr-hn]

I figured GPS-guided bombs would be the only thing impacted. Cruise missiles match terrain to what's stored in memory to know where to drop.

[philwelch]

Depending on the plane, there are cases where a full systems failure knocks out every means of navigation other than "Mark I Eyeball": http://www.defenseindustrydaily.com/f22-squadron-shot-down-b...