[time-nuts] Health of GPS constellation questioned

Rob Kimberley time.bandit at btinternet.com
Thu Sep 7 09:07:24 EDT 2006


John,

Had similar problem on my Garmin Quest after I had a windscreen changed on
my car. Apparently the new one had a coating on it which degraded signal
levels. Got round it by putting an external mag based antenna on roof.

Rob Kimberley 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Neon John
Sent: 07 September 2006 12:33
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Health of GPS constellation questioned

On Thu, 7 Sep 2006 13:12:07 +0200 (CEST), "Bart Smit" <bit at pipe.nl>
wrote:

>
>On Wed, September 6, 2006 5:22, Christopher Hoover said:
>
>> [ the story seems overblown to me, but still worth sharing.  follow 
>> the last link for some real data. - ch ]
>
>The last link is interesting indeed. Seems that the problems are more 
>perceived than real, with the GPS constellation operating well within 
>spec, but users wanting more.

A more basic question.  Do these degradations affect ordinary users?
The reason I ask is that I have a GPS navigation system on in my truck
24/7 and use it every waking hour (I'm a retired engineer who's living a
childhood fantasy - driving a long-haul 18-wheeler :-)  Fairly frequently I
experience fairly long intervals where the system goes completely dead.  The
satellite screen is all red - the system knows where the satellites are but
no signal is received.  This can last for miles.  I've relocated the
receiver, even stopping and removing the receiver from the truck just in
case EMI was the culprit.  Then just as quickly, the receiver gets lock and
everything is fine.

The distance traveled - sometimes 10 miles or more - during an outage is
such that ground interference can fairly confidently be eliminated.
Almost all my running is on open interstates so ground factors can be
eliminated.

I've gotten curious enough about this to bring along another receiver but so
far nothing has happened to give me an opportunity to check with the second
receiver.

The system is Street Atlas with the Delorme Earthmate hockey-puck receiver.
I've had this system about 4 years and it is only in the last few months
that this has started happening.  I'd attribute this to something in my
receiver except that I recall also having occasional loss of signal on my
other receiver, a Magellan Meridian Platinum, which I just attributed to
"stuff happens".

John
---
John De Armond
See my website for my current email address http://www.neon-john.com
Cleveland, Occupied TN Don't let your schooling interfere with your
education-Mark Twain

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