[time-nuts] Using digital broadcast TV for timing?

Magnus Danielson magnus at rubidium.dyndns.org
Thu Feb 9 21:16:57 UTC 2012

On 02/09/2012 07:21 PM, Chris Albertson wrote:
> On Wed, Feb 8, 2012 at 11:02 PM, Hal Murray<hmurray at megapathdsl.net>  wrote:
>>> Other than LightSquared, an event that made GPS go away would most likely
>>> eliminate most interest in ultra accuracy time keeping.
> By "went away", I meant locally,  as be being jammed or spoofed.
> Possibly a car drives into a tunnel and then from the car's point of
> view GPS "goes away".
>  From a military point of view all it takes to knock out GPS is to
> suicide truck-bomb both ground control stations or simply jam the GPS
> uplinks so the stations are unable to send commands.   But The
> question was more theoretical then practical.

Let's assume that the physical safety of the ground control center is 
there, and just have a look at the jamming of up-links. Jamming the 
up-links would be a bit of a difficult task, since there is not one but 
several up-links, also you would need to high-energy jam all the birds 
as you would not know when they would get their commands. Add their 
capability of cross-link communication and ability to uphold a decent 
situation in autonav for ground station outage of up to 180 days. Oh, 
both uplink and cross-link is encrypted and fairly jam-resistant. 
Cross-link has nulls towards earth and only a half-decent gain in 
certain angles.

All that comes out of public sources. It would take a bit of resources 
to do a global GPS outage, and to maintain it you would expose yourself 
over a long time such that you would be found and well, let's assume 
that your antennas will not take kindly to the things being dropped at it.

Regional outages is much easier.


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