[time-nuts] Missing GPS satellites

Raj vu2zap at gmail.com
Fri Mar 26 03:01:45 UTC 2010


Rob, I am 13N 77E approx.

Bob, I checked everytime and no birds. I setup two GPSDOs with seperate antennas and both went to hold over.

Its been happening ever day at some times. Even I get the error on this page
http://www.n2yo.com/whats-up/?c=20

Lady heather says the doppler is high or something and satellites not usable. Sometimes there are 3 sats overhead and none usable!

At 26-03-10, you wrote:
>What's your latitude Raj?
>
>Rob K
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Bob Camp
>Sent: 25 March 2010 11:15 PM
>To: Discussion of precise time and frequency measurement
>Subject: Re: [time-nuts] Missing GPS satellites
>
>Hi
>
>I still think it's a bird on the antenna.
>
>Bob
>
>On Mar 25, 2010, at 7:11 PM, Magnus Danielson wrote:
>
>> J. Forster wrote:
>>> From an unnamed, but VERY credible source:
>>> 
>>> "> It might be that the DoD is turning the civilian signals off in combat
>>>  
>>>> areas to deny GPS to the Taliban and others.
>>>>    
>>> 
>>> Quite possible.  This countermeasure was discussed more than ten years
>>> ago.
>>> 
>>> It is possible to turn of the civilian signals -- or to leave then on
>>> but _jam_ them within a selected area -- without interfering with US
>>> military use of the satellites.  A modern military does not need the C/
>>> A code to acquire lock on a satellite.  It can acquire the encrypted P
>>> code directly."
>> The preferred method of controlling the access to GPS within a region is
>> GPS jammers, and the full set of efforts being spent on strengthening
>> the allied forces availability to signal is to ensure ability to survive
>> from jamming signal, which includes removing need for C/A locking prior
>> to Y-code lock with direct lock methods, transfer of time, solutions and
>> ephemeris data, and eventually means to direct additional power towards
>> the area and the improved M-code.
>> 
>> Turning of the C/A code of a satellite will effect the 1/3 of the earth
>> area that it sees, and for that to be effective in a certain area, you
>> need to do that to 6-8 sats to turn it off, and that will significantly
>> reduce the GPS availability for so large geographical areas that things
>> they want to work will run closer to failure. So no, turning of C/A code
>> is not what they want to do it. They can, but they want to avoid it.
>> 
>> Cheers,
>> Magnus
>> 
>> 

-- 
Raj, VU2ZAP
Bangalore, India. 




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