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How The FCC Plans To Destroy GPS – A Simple Explanation

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Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#51

Post by derleth »

X-Istence wrote: post #43
derleth wrote: post #39

Earlier quoted context omitted.

Well, they do: Doctors and other medical professionals have come to rely on cell phones to be notified of emergencies quickly enough to save lives. If they are blocked, there's a realistic chance lives will be lost for no good reason. (I've never heard of a good reason to block cell phone transmissions. It always seems to come down to trying to enforce some vision of politeness via technical means, which doesn't take…

This is why it should be possible for theatres and the like to set up alternate base stations that cell phones connect to, this way 911 calls and text messages incoming may still be delivered but no incoming/outgoing calls may be connected.

In the scenario I'm describing, the doctor is going to the theater when they get a call from the hospital saying there's someone there who needs their skill. (It's actually in their contract that, while they're on-call, they have to remain within a certain amount of travel time from the hospital so they can get there in time. This does affect home purchases.) If their cell phone is blocked, the call is missed and someone may very well die.

You could (presumably) attempt to fix this with technology. It might even work for a while, but when it breaks, someone could very easily die. And they'd have died of someone else's dislike for cell phones, which is not a good reason.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#53

Post by philwelch »

mkr-hn wrote: post #15
kpeel wrote: post #12

Earlier quoted context omitted.

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.

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.

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...

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#54

Post by wtallis »

marshray wrote: post #23

It's possible the LightSquared transmitters will be far more directional than the Garmin test gives them credit for. They may not run full power all the time anyway. Regardless, it's generally the responsibility of the receiver to ignore signals in another part of the same band, and this is a different band entirely. Perhaps some receivers are built as cheaply as possible and don't have the best filters. If they all…

Why would the military want an array of tens of thousands of low-power emitters when a few klystrons will do? 10+ megawatts pulsed output in a single L-band device is not hard to achieve, and much higher can be achieved if you're willing to accept the higher cost and shorter lifespans associated with running at higher voltages.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#55

Post by jcr »

(sigh) The article was written by an alarmist moron trying to push his own agenda, and most likely, pushing it for his own profit.

The only real problem is GPS equipment manufacturers intentionally cut corners and costs by FAILING to implement proper bandpass filters.

When the LightSquared towers get turned on, and customers who bought incorrectly designed garbage from the likes of Garmin, the result will be simple: The equipment makers will get sued in massive class action law suits for selling broken equipment. And yes, the manufacturers deserved to be sued for cutting corners on bandpass filters and selling junk since THEY HAVE ALWAYS KNOWN the adjacent spectrum frequencies could be used at any time.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#56

Post by marshray »

X-Istence wrote: post #42
marshray wrote: post #34

Earlier quoted context omitted.

OK I see it now. It looks like everything in that adjacent band had previously been designated space-to-earth. I suppose it would be reasonable for an engineer to assume a receiver is not going to end up within a few KM of a 15 KW transmitter at those frequencies.

At high power you can overpower adjacent frequencies wether you have good band filtering on it or not. For example a 2 Watt FM transmitter at 100 Mhz can easily overpower radio's tuned to 95 Mhz just because of its power, even with the appropriate filtering.

The internationally-agreed upon plan for the adjacent band was to have all the transmitters in orbit and all the receivers on the ground. So I don't think a 2W transmitter in orbit is going to overpower receivers in a different band.

40,000 of 15KW transmitters on the ground may be another matter.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#57

Post by marshray »

wtallis wrote: post #54
marshray wrote: post #23

It's possible the LightSquared transmitters will be far more directional than the Garmin test gives them credit for. They may not run full power all the time anyway. Regardless, it's generally the responsibility of the receiver to ignore signals in another part of the same band, and this is a different band entirely. Perhaps some receivers are built as cheaply as possible and don't have the best filters. If they all…

Why would the military want an array of tens of thousands of low-power emitters when a few klystrons will do? 10+ megawatts pulsed output in a single L-band device is not hard to achieve, and much higher can be achieved if you're willing to accept the higher cost and shorter lifespans associated with running at higher voltages.

Yeah, I dunno. How about

1. They can repurpose existing infrastructure with just a software change 2. Nobody has to pay for much out of their own budget or build it in anyone's back yard 3. Nobody has to declare it under any treaties or such 4. The system can receive as well as transmit 5. It's engineered and tested for continuous operation. There may even be excess capacity available almost for free 6. The system is massively redundant and supplies its own power and backup generators 7. More is better 8. Why not? 9. If it saves one child... 10. ... 11. Profit!

and so on. Just tossing out wild ideas here.

If only Nikola Tesla were alive to see this plan, he would certainly approve.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#58

Post by marshray »

crikli wrote: post #46
marshray wrote: post #35

Earlier quoted context omitted.

Perhaps you can explain why the FCC is granting this license/waiver even in the face of vehement opposition from a broad collection of GPS manufacturers and aviation groups? http://licensing.fcc.gov/cgi-bin/ws.exe/prod/ib/forms/report...

The opposition was vehement, yes, but limited to strongly worded letters from (mostly) small general aviation companies. No Boeings, no American Airlines, no 'big guns' with be-suited lawyers to make the FCC wake up and smell the jet fuel. Wait until a couple airliners go missed on RNAV GPS approaches in low IFR conditions (visibility < 1 mile or cloud ceilings at less than 500 feet). The airlines will raise hell, th…

I think this company is a customer of Boeing's. Boeing builds their satellites.

As for the airlines, they are so heavily regulated that they might think twice about filing official comments on stuff like this without permission. No doubt FAA and FCC are talking about this even if it's not official. Their offices are only a few blocks away.

Re: How The FCC Plans To Destroy GPS – A Simple Explanation

#59

Post by derobert »

X-Istence wrote: post #45
wickedchicken wrote: post #28

I thought GPS was spread spectrum which would make it resistant to these kinds of interference? After all, GPS satellites broadcast at the same frequency as each other, that's the genius of how GPS works.

By the time the GPS signal reaches earth it is at a very low power, think milliwatts. Lets think of it as you trying to eavesdrop on a meeting. You have your ear pressed on a big thick wooden door that lets very little sound through, you are attempting to hear so you have everything around you very quiet and try your best to hear that very faint sound of your boss talking about the companies plan to fire everyone. No…

GPS signal strength at Earth's surface is -130dBmW, so that'd be attowatts... A GPS satellite capable of 0dBmW would be truly scary; it'd have about a petawatt of electrical supply.

See, e.g., http://gpsinformation.net/main/gpspower.htm

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