"Brian Utterback" <[email protected]> wrote in message
news:[email protected]...
[]
There are two sides with different figures. The GPS industry says that
500,000,000 units would be affected. The company LightSquared says it is
really 200,000. The DOD standards for GPS receivers issued in 2008 says
that devices should require no more than a 4 MHz gap between bands, and
LightSquared is allowing a 23 Mhz gap, but GPS manufacturers say that
they need a 34 Mhz gap. Further, the DOD warned GPS manufacturers in
2000 that they were not sufficiently selective.
Ouch. The GPS manufacturers took short cuts, and just like the Netgear
fiasco, there are millions of units that will be affected with no way to
fix them. And it is the users that are going to get hit.
Interestingly, the FCC has said to both LightSquared and the GPS
industry to cut the BS and come up with the real figures.
--
blu
While not identical, we have experience in the UK of high-power pager
transmitters being placed adjacent to a 136-138 MHz satellite band. In
practice, it is near impossible to filter out the pager transmissions so
if you live near a pager transmitter, satellite reception is completely
ruined. It didn't help that some pagers were actually placed /inside/ an
internationally protected frequency band.
Anyone with experience of RF design will soon tell you that at 1.5 GHz a 4
MHz separation is completely unrealistic, and 23 MHz is very tight.
Something nearer 50 MHz is getting realistic. Don't forget the sideband
energy from these digital transmissions, and the below zero
signal-to-noise ratio of GPS.
I do hope there is a satisfactory resolution.
Cheers,
David
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