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

Bob Camp lists at rtty.us
Sat Jun 11 14:06:19 UTC 2011


Best guess - a few million timing receivers are out there. Probably not over 
ten million. To replace them at "new" prices, figure $5000 each including 
the labor. Lots of variables, might be twenty billion dollars if you did a 
straight swap.
Changing out antennas would be cheaper for the hardware and likely more for 
the labor if a tower is involved. Might be half the price of doing the 

Quick math:

Take a tower count (say 250,000). Assume each system on the tower has doubly 
redundant GPS.  Take a reasonable number of systems per tower (at least 1 
likely >4). That gets you to a million pretty quick. Add to that the 
non-cell tower telcom stuff and you likely double or triple the number.


-----Original Message----- 
From: Hal Murray
Sent: Friday, June 10, 2011 10:01 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS interference and history...

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 
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 
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 

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

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