[time-nuts] From GPS World - Lightsquared has been given the goahead

Rex rexa at sonic.net
Wed Feb 2 22:06:24 UTC 2011


On 2/2/2011 7:25 AM, jimlux wrote:
>
>
> I got the impression that it wasn't modeled, but was an actual field 
> test of some sort.  I'll have to go back and reread.
>
> But, it's possible that the consumer receiver has better multipath and 
> interference rejection, if only because it's newer. Aviation stuff 
> takes longer to go through the approval cycle, so it tends to lag 
> consumer electronics in terms of technology adoption.
>
>

 From the paper submitted by the GPS manufactureres to the FCC
http://www.gpsworld.com/gnss-system/signal-processing/lightsquared-jamming-report-11030

it seems they simulated the Lightsquared signal with test equipment and 
made measurements in an anechoic chamber of effects on GPS signal 
reception to a couple of popular GPS receivers. Using this data they 
extrapolated real-world effects with path loss calculations. Ironically, 
it probably wouldn't be legal or safe to make the jamming measurements 
in a real, open space, environment.

The paper says the Lightspeed transmitters can be up to around 15 kW 
EIRP in a band right adjacent to GPS. I would think filtering out that 
signal to avoid overload would be a daunting task.






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