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AuntPeggy

AuntPeggy

Final Approach
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Namaste
<snip>The Federal Communications Commission (FCC) granted mobile-satellite services operator LightSquared a waiver allowing it to repurpose the satellite spectrum immediately neighboring that of GPS. Given pilots’ widespread use of GPS and the FAA’s transition from ground-based to satellite-based navigation and surveillance (known as NextGen), AOPA petitioned the FCC to reverse the authorization until LightSquared can prove it will not interfere with GPS.
<snip>
The coalition cites initial technical analyses that indicate that low-powered GPS signals would receive substantial interference from LightSquared’s network of high-powered, close-proximity ground transmissions.
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http://www.aopa.org/advocacy/articles/2011/110310save_our_gps.html
 
We don't need no stinkin' guvmint gee pee sss. Real pilots use VOR.

/kidding
//would be annnoying
 
We need torches and pitchforks, we must march on Washington now! (Like that would change anything)

LightSquared has made their honest Congressional campaign contributions, it's a go. Doesn't matter what we think.

John
 
No worries. I trust the government to do the right thing. :rolleyes2:
 
Well, we always have LORAN as a robust, proven and developed backup.
 
Gary F said:
I thought the primary mission of the FCC was to prevent frequency interference problems.
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No it isn't. The FCC is charged to regulate commerce that uses radio and wires. The FCC does listen to industry experts about interference issues and establishes, with industry input, rules concerning interference. When those rules are broken the FCC can step in and is also able to enforce the regulations.



Gary F said:
That should not be so hard, get a list of the frequencies in use and check for conflicts before assigning a new frequency.
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But what constitute unwanted interference and unacceptable levels of interference is hard. Often there are huge battles between interested parties about what really will and will not interfere. Lots of money in studies, simulations, lobbying, etc. get spent. The war between satellite and terrestrial services has been going on for a while and has really been heating up over the last few decades as more and more services are filling the useful frequency bands.
 
ScottM said:
No it isn't. The FCC is charged to regulate commerce that uses radio and wires. The FCC does listen to industry experts about interference issues and establishes, with industry input, rules concerning interference. When those rules are broken the FCC can step in and is also able to enforce the regulations.
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I don't understand. If it's not the FCC's responsibility to assign frequencies, whose responsibility is it?

The radio spectrum is the radio frequency (RF) portion of the electromagnetic spectrum. In the United States, regulatory responsibility for the radio spectrum is divided between the Federal Communications Commission (FCC) and the National Telecommunications and Information Administration (NTIA). The FCC, which is an independent regulatory agency, administers spectrum for non-Federal use (i.e., state, local government, commercial, private internal business, and personal use) and the NTIA, which is an operating unit of the Department of Commerce, administers spectrum for Federal use (e.g., use by the Army, the FAA, and the FBI). Within the FCC, the Office of Engineering and Technology (OET) provides advice on technical and policy issues pertaining to spectrum allocation and use.
http://www.fcc.gov/oet/spectrum/

ScottM said:
But what constitute unwanted interference and unacceptable levels of interference is hard. Often there are huge battles between interested parties about what really will and will not interfere. Lots of money in studies, simulations, lobbying, etc. get spent. The war between satellite and terrestrial services has been going on for a while and has really been heating up over the last few decades as more and more services are filling the useful frequency bands.
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I agree but GPS is so important that I would expect that any frequencies that might interfere should require careful scrutiny before they are assigned.
 
Gary F said:
I don't understand. If it's not the FCC's responsibility to assign frequencies, whose responsibility is it?
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You are asking two different questions. Assigning a frequency and ensuring that they do not interfere are not the same thing. Notice at best the FCC OET offers "advice." SIGH! :incazzato:Mostly the interference issue is sussed out by industry folks getting together, with an FCC guy in the room and everyone beats the crap out of each other until it is time for open bar. Then they all get to be buddies and work out a solution. This can take months to years.

For instance the FCC has assigned as a primary user of 2.4GHz Amateur radio stations. But they have also issued those same frequencies to unlicensed wireless LAN and telephone systems. All the FCC added was a statement that said "on a non-interfering basis." IOW youse is on your own. If I blast your WiFi with my ham radio tough luck. However you mess with my satellite downlink on 2.4GHz and I can have the FCC shut you down.

The FCC band plans based on industry and military inputs. The NTIA carries a lot of weight in those discussion and is who companies really have to convince that interference is not going to happen. Interference is a fact of life and what the FCC will broker are rules on how to mitigate it.

Here is a typical band plan.
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=2682
 
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So far all I see is a paid-for campaign orchestrated by L2's competitors such as Verizon and AT&T and its bogus FUD about GPS interference. I hoped someone would cut through propaganda at least at pilots' forum, but no luck. You guys are making me to do the research myself :-)
 
zaitcev said:
So far all I see is a paid-for campaign orchestrated by L2's competitors such as Verizon and AT&T and its bogus FUD about GPS interference. I hoped someone would cut through propaganda at least at pilots' forum, but no luck. You guys are making me to do the research myself :-)
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It appears that Garmin and Trimble raised the issue, not LightSquared's competitors.

http://www.gpsworld.com/gnss-system...us-gps-jamming-fcc-approved-broadcaster-11029

http://www.insidegnss.com/node/2471

In the attached pdf file on page one of the executive summary they report that a Garmin GNS430W is completely jammed by LightSquared transmitters over 5.6 miles away.
 

Attachments

Gary F said:
http://www.insidegnss.com/node/2471

In the attached pdf file on page one of the executive summary they report that a Garmin GNS430W is completely jammed by LightSquared transmitters over 5.6 miles away.
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Thanks. This is very interesting:

“Because the GPS interference concerns stem from LightSquared’s transmissions in its authorized spectrum rather than transmissions in the GPS band,” the FCC order reads, “the Commission expects full participation by the GPS industry in the working group and expects the GPS industry to work expeditiously and in good faith with LightSquared to ameliorate the interference concerns.”
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The question now, I guess, is if the garbage Garmin receivers share the front-end that filters poorly with the expensive aviation equipment such as 696. I'm wondering what the characteristics of common filters in the band looks like. If Garmin has a bell shaped one, they will pick up L2's signal. Remember that there is no ideal filter in RF.

-- Pete
 
Gary F said:
I thought the primary mission of the FCC was to prevent frequency interference problems. That should not be so hard, get a list of the frequencies in use and check for conflicts before assigning a new frequency...
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Frequencies are like airplane seats. The airline reservations ensure that no two butts are assigned the same seat. But sometimes the butt sitting next to you doesn't fully confine itself to the space allocated to it.

The issue of "will this application interfere with that application" is a little bit complicated. Transmitters don't necessarily transmit 0 power outside the bounds of their assigned frequency band. It's a "how much is too much?" question.
-harry
 
zaitcev said:
The question now, I guess, is if the garbage Garmin receivers share the front-end that filters poorly with the expensive aviation equipment such as 696. I'm wondering what the characteristics of common filters in the band looks like. If Garmin has a bell shaped one, they will pick up L2's signal. Remember that there is no ideal filter in RF.

-- Pete
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A filter with 40-60db attenuation a couple MHz below the GPS L1 frequency spread and less than a half DB inband (about what's needed) isn't cheap if it can even be made to work over the required temperature range. Much of that filter would need to be inside the antenna which is both space constrained and exposed to a very wide temp range. The filters in the 530W that was used in the test are probably as good as needed if someone wasn't pumping out a big signal 10,000 times closer to the receivers than was expected to be allowed per the FCC's own rules.
 
The received GPS signal is approximately -160 dbW. Which works out to about 0.0000000000001 watts. If you sneezed around 1.5 GHz you'd jam a Garmin.
 
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