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sci.geo.satellite-nav (Global Satellite Navigation) (sci.geo.satellite-nav) Discussion of global navigation satellite systems (GNSS). Topics include the technical aspects of GNSS operation, user experiences in the use of GNSS, information regarding GNSS products and discussion of GNSS policy (such as GPS selective availability).

Congress, FCC Moves Closing Out Options for LightSquared



 
 
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Old February 3rd 14, 10:07 PM posted to sci.geo.satellite-nav
Alan Browne
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Posts: 1,339
Default Congress, FCC Moves Closing Out Options for LightSquared

On 2014.02.02, 16:30 , J. J. Lodder wrote:
Alan Browne wrote:

On 2014.02.02, 13:30 , J. J. Lodder wrote:
Alan Browne wrote:

On 2014.02.02, 04:49 , J. J. Lodder wrote:
Joop wrote:

On 1-2-2014 18:00, Alan Browne wrote:
On 2014.01.31, 18:58 , Sam Wormley wrote:
To meet the financing conditions of the
plan, the commission must take half a dozen actions, including
approving the use of certain segments of spectrum and permitting
signal power limits comparable to other 4th Generation LTE wireless
communications networks.

The whole thing is magnificently perplexing.

It would seem to little old me that the best use of that spectrumis as
originally planned: from geostationary satellites with no more than a
few uplink locations with very directional antennas with very low
sidelobes.

On the other hand - the radio spectrum is getting more and more crowded
every day. It would be good for radio interoperability in generalif
GPS receivers would be able to cope with strong signals on nearby
frequency's, or - at least - step away from using wideband and almost
unfiltered preamplifiers at the antenna.

Fourier forbids,

Fourier forbids simplicity, not compromise.

There is no compromising with a near neighbour
who is many decades stronger,


You can filter with very sharp cutoff in front of the receiver at a cost
in components and receiver size. In some applications (esp. surveying)
it's not desirable as such filtering will reduce precision by a small
amount.

Whether it would have a great affect on aviation receivers, I'm not all
that sure - esp. since high precision approach would be with LAAS which
would easily compensate for whatever losses would occur with the sharp
cutoff filter.

OTOH, there are 10's of thousands of TSO'd GPS receivers installed so
the cost of retrofit and certification would be enormous.

For the telecoms industry it would be of high impact as well. (190,000
towers in the US alone - each tower having at least one GPS receiver -
usually several as there are several providers per tower).

The real issue is that spectrum was allocated for space based
transmission so by the time the signal reached the earth (incl.
airspace) the signal level would be tolerable to GPS receivers.


Fourier dictates that his sidebands will be in your band.
No amount of filtering at the receiver side can cure that,


First off it's not 'side bands' of any sort, just that the GPS receivers
are sensitive enough to a wider than nominal bandwidth. This would not
be an issue except for L^2 game changer with thousands of
omnidirectional broadcast at ground level all over the US. That would
definitely be picked up by nearby (many km) GPS receivers on the surface
and up to considerable altitude.

Suppression of out of band-of-interest has been around for a long time.
Otherwise a lot of systems would be jammed by adjacent signals coming
through antenna systems which are usually much broader band sensitive
(if not optimally) than the band of interest.

--
“Everybody has a plan until they get punched in the face.”
- Mike Tyson



 




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