Words of Advice:

"If Something Seems To Be Too Good To Be True, It's Best To Shoot It, Just In Case." -- Fiona Glenanne

"Flying the Airplane is More Important than Radioing Your Plight to a Person on the Ground
Who is Incapable of Understanding or Doing Anything About It." -- Unknown

“Never argue with stupid people, they will drag you down to their level
and then beat you with experience.” -- Mark Twain

"John Wick didn't kill all those people because they broke his toaster." -MickAK

"Everything is easy if somebody else is the one doing it." -- Me

"What the hell is an `Aluminum Falcon'?" -- Emperor Palpatine

"Eck!" -- George the Cat

Friday, June 17, 2011

Do You Still Remember How to Read a Road Map?

You might want to refresh your map-reading skills, for a company called "LightSquared" wants to implement a nationwide wireless network. But their frequencies (which the chowderheads at the FCC let them have) are right next to the GPS frequencies.

So what you have are pretty weak signals coming down from satellites 12,500 miles up, which your GPS receiver will need to pick up through the noise broadcast by a transmitter that is virtually next door.

This is what your GPS receiver is looking for:
The GPS signal strength measured at the surface of the Earth is about –160dBw (1 x 10–16 watts), which is roughly equivalent to viewing a 25-watt light bulb from a distance of 10,000 miles.
That weak signal is because the satellites' transmitters have a signal strength of 50 watts. LightSquared's towers will have transmitters with a signal strength of 1,500 watts. GPS receivers would have to pick out those extremely weak GPS signals through that strong noise. The tests seem to be revealing that they cannot do it.

You may not know this: Modern agricultural equipment is very dependent on GPS. The folks at John Deere did some testing and found this: Deere receivers registered impact of and interference by the LightSquared signal as far away as 22 miles from a transmitter. Further, the company has found no practicable technical solution to the problem.

The FAA wants to replace its ground-based navigation aid system with GPS. Smaller airports had instrument approaches that used non-directional beacons (NDBs) for navigation. The FAA has been decommissioning NDBs and replacing the NDB approach procedures with GPS approaches. The LightSquared network would likely completely fuck those things up.

LightSquared's network would most likely screw with vehicle navigation systems. No doubt that they have bought off their share of congressmen. But between the airlines, agriculture, trucking, public safety, the car companies and the motoring public, my bet is that LightSquared is going to lose this fight.


w3ski said...

I Love computer teck but I just have a thing against GPS.
I live on a dead end road and one day my dogs are all upset so I go have a lets see.
Some couple with their GPS had turned off the highway and down my road trying to find the local Casino.
They were sure that "this" was the road they wanted, but the rock ruts kinda swayed thier confidence.
It took a bit but I finally convinced them to go back.
Shoulda let them go get stuck at the real end of the road.
GPS !! I learned to read a map and compass as a young lad and it's Never led me wrong yet.

Nangleator said...

National fucking security problem. Fix it with lawyers and judges, or bullets and bombs. We need GPS. We don't need any more terrorist attacks on our infrastructure.

Eck! said...

Well a few things.

The FCC is encouraging things but the actual license granted was conditional for testing.

Now every RF engineer I know, and my self as a RF engineer have looked at that and said "this is stupid".

Lightwhatever claims improved gps with more selectivity an cope with it but the BEST and most expensive GPS in airplanes get totally wiped out at 6miles and suffer degradation at 12.
Also at those frequencies adding that selectivity makes the receiver deaf
and that really really weak signal required a good receiver to work or way bigger antennas, unportable antennas, un-aerodynamic antennas, and yes costly antennas.

Stupid stupid Federal Cookie Company.
They are going to repeat the GPS version of the BPL fiasco again!


Comrade Misfit said...

There must be tens of millions of GPS receivers out there by now. The idea that everyone will replace them to suit LightSquared is, well, stupid.

Eck! said...

It's more than stupid.

It's in smart phones, tablets, Onstar and a log list of other neat things. In some cases the cost would be borne by the vendor and retro fitting and new FCC approval for the GPS is _very_ costly.

In many cases the infrastructure damage would be extensive.

Sectionals, VOR and DR. Forget they also killed Loran on a cheap out.


Anonymous said...

Sold my boat when Loran went out.
Won't buy ANY electronic nav aids now days. Maps or stay the frak home.
Thanks a lot, Uncle Sam.

Sarah said...

It's not going to happen. The FCC was asleep at the switch again ( remember the 121.5 ELT rule? ) and is being spanked.

In your original post: It's "NDB", non-directional beacon, not "NBD". No Big Deal. :)

Comrade Misfit said...

Fixed it, thanks.

Antrax said...

An interesting take on the GPS/Lightsquared situation from Praxis