[time-nuts] GPS interference and history...

Hal Murray hmurray at megapathdsl.net
Sat Jun 11 02:01:41 UTC 2011

lists at rtty.us said:
> There's an enormous amount of gear out there that gets timing off of GPS. 

That's an interesting claim.  Does anybody have any data on the usage of GPS 
for timing?

I assume there is one in every cell tower and one in every 911 call center.  
Are there other large categories of users?

What would it cost to replace all of it?  If you wanted to do something like 
that, what would "it" cover?  How about people like us running old recycled 
gear?  (Z3801A, ThunderBolt, ...)

I think I saw one last week.  It was on a river level measuring station on 
the Sacramento River.  It was a small block building.  There was an antenna 
pointing up into the sky.  I assume there is a satellite up there.  There was 
also a small (~3 inch dia) hemisphere antenna. I assume it was GPS.  (They 
had power going into the building (no solar panels) so it should have been 
simple to get a phone line too.)

I'm not sure why they need GPS at the recording house.  They know where it is 
so timing is the only use I can think of.  But they could also get that at 
the receiving end.  Millisecond accuracy isn't helpful.  Second level 
accuracy might be interesting if something breaks and you want to know when 
the wave got to downstream stations.  The risetime is probably over a second.

These are my opinions, not necessarily my employer's.  I hate spam.

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