There's a good piece in the Economist about how a FCC screwup allocated frequencies to a wireless Internet firm that are adjacent to the GPS frequencies. Now the firm wants to roll out its network, and if the FCC lets it go ahead, we're going to all have to start soldering filters on our GPS modules if we want them to keep working. (I hope wise minds will intervene and ensure that this doesn't come to pass, but it's hard to have confidence in the political system at the moment).
Here's the root of the problem:
The ultimate source of the trouble is a decision made in 2003 by the Federal Communications Commission (FCC) to grant special dispensation to a broadband satellite operator called SkyTerra, allowing it to fill gaps in its coverage by means of ground-based transmitters. SkyTerra’s chunk of spectrum (1,525-1,559 megahertz) abutted a crucial frequency (1,575 megahertz) used by GPS satellites. However, SkyTerra’s signals being mere whispers from space and its few proposed ground stations designed to operate at low power, any threat to GPS was dismissed as highly unlikely.
Everything changed when Harbinger Capital Partners, a New York-based investment firm founded by subprime-mortgage billionaire Philip Falcone, bought SkyTerra in 2010 and renamed it LightSquared. For Mr Falcone, the attraction was three-fold: SkyTerra’s swathe of under-used frequencies; its licence to provide a nation-wide internet service; and, above all, the FCC’s waiver allowing it to use ground-based transmitters where satellite reception was poor.
Mr Falcone quickly persuaded the FCC to rewrite the former SkyTerra licence. Instead of being conditional on offering an internet service primarily by satellite, with ground stations filling in only where satellite coverage was inadequate, the revised licence accepts that the network will rely almost exclusively on terrestrial transmitters.And not just low-powered ones for serving inner cities. The company intends to build a broadband wireless network comprising 40,000 base-stations across the United States. These stations will put out 15,000 watts apiece. Typical mobile-phone transmitters in urban areas radiate between five and ten watts. Even the 100-foot towers used in open countryside transmit no more than 60 watts.
Comments
A prudent solution proposed in the Schlesinger, Parkinson letter referenced above:
"We strongly recommend that the Commission rescind its conditional wavier and not allow a change in the structure of the MSS band that abuts GPS to allow t ransmissions that interfere with GPS. Another frequency band must be found, well away from GPS that allows LightSquared to compete with the other broadband suppliers and does not jeopardize US infrastructure, ImpOSing unnecessary costs to the many mi l l ions of current GPS users."
Just give them another freq band.... BRILLIANT!
Pacemakers won't be the only issue... think what this would do to the tanning-bed industry...obsolete overnight!
And why buy a microwave oven when all you have to do is wave your dinner out the window for a few minutes, and Presto!
"The two co-chairs of the U.S. National Advisory Board for Space-Based Positioning, Navigation, and Timing, the Hon. James R. Schlesinger and Dr. Bradford Parkinson, have delivered an official, strongly worded letter today to Julius Genachowski, chairman, Federal Communications Commission."
"Schlesinger, Parkinson Address FCC: Rescind LightSquared Waiver"
http://www.gpsworld.com/gnss-system/news/schlesinger-parkinson-addr...
http://www.gpsworld.com/gnss-system/pnt-advisory-board-letter-aug-3...
Is there a source (other then the economist..) that proves the 15kW transmission power? First guess would be it´s a misunderstanding because for a bi directional service like internet, brodcast-like powers don´t make too much sense to me. The reason you need so many towers normally is that you have to be able to receive the weak signls of the phones etc..
And I suppose a 15kW tower would have more problems other then GPS... Just think about the security radius for heart pacemakers... Hard to imagine in urban areas.
Bad thing anyway. Reminds me in a way of the problems in short wave bands we have with PLC systems. Not a safety critical aplication but you learn it´s hard to fight against these problems...
@Michael - If anyone can do it, Honeywell/Ratheon can! I use their products extensively on my old boat.
I have a Raytheon GPS/radar chartplotter integrated into my VHF com using a nmea string, soon I'll have the marine version of ADS-B (AIS). The MARPA function on the Raytheon radar is very impressive - lots of functionality in a small package for little cash.
For battery-powered avionics suites, nothing beats the current glider technology, I ran two glide computers, a digital flight data recorder (Volkslogger), moving map display, VHF com, electric vario, ELT, transponder, and a dragmeter on two batteries. I believe this is old technology - the future is bright!
http://www51.honeywell.com/aero/common/documents/myaerospacecatalog...
I'm thinking there's a big opportunity here for people with electronics skills to fix Falcone's problems - and many more to come as we squeeze the spectrum - and maybe expand it out of the radio bands and into the light bands? I know guys who are doing clever stuff with LIDAR.
The farming community has been jumping up and down about this for the past few months. They are in a tight spot as they would benefit from high speed internet in rural areas but they see the potential degradation of gps signal and the impact that could have on precision ag equipment (those tractors really do drive themselves) as real issue.
I was working in Europe when FM immunity became a rule that we were required to comply with to protect aircraft VHF radios from FM signal creep (for lack of a better technical description). Then later, we went to .25mHz channel spacing (in the US as well) because we needed more and more channels in the aviation frequency spectrum - so I suspect (but have no real knowledge or insight on this specific LightSquared issue) that technology will save us from damaging the GPS spectrum. There increrasing demand for more of the radio spectrum and it is only so big - so clever electronic engineers will get busy and sort this issue out - along with many others that will manifest in the future.
Here's one - how about somebody develop a home-brewed, open-source sUAS (hobby UAV) transponder with Mode S and/or tcas capability so someday we can legally enter the NAS. It would be cool if the average Joe (like me) can fly his model UAV in the NAS safely (OK maybe up to 1500' AGL or so) and the odd Taylorcraft or C-172 with ADS-B can see us and avoid us... automatically. In the glider world, they are installing small transponders running on batteries.
Jack could be right. Without GPS in their eye-phones the average human will not be able to find their way home and will be forced to seek shelter in the nearest cave or hollow log and the path will be clear for our invasion. All hail Zardog of the Ogort system.
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