[time-nuts] Nav Receiver Sawtooth Correction?

Chris Albertson albertson.chris at gmail.com
Sun Mar 23 22:24:29 EDT 2014

What you are seeing in position error is a random noise.  There is no
pattern to it and it is not predictable.  A sawtooth error is very
nice and regular looking.  It's not "noisy" and can be predicted in
advance.    Possition error is not at all like sawtooth.

I think what you CAN do is look at the size of the error.  Then you
adjust the gain on the loop control based of the measured error sigma.

On Sun, Mar 23, 2014 at 6:30 PM, Bob Stewart <bob at evoria.net> wrote:
> Hi Ignacio,
> Thanks for the response.  I've got a UT+ in the parts box.  But that's not the problem I'm trying to solve.  I'm trying to make the best GPSDO that I can make using a nav receiver at the moment.  Call it an obsession if you like.  It's OK if I don't have corrections to the nanosecond for each PPS.  But I can see the nav receiver wandering around; especially on cloudy days, (the antenna is in the attic, so that's about the best I can do for that) and it just seems to me that I should be able to do a general correction for nav position errors.  Sorry if my naive posts are starting to get on people's nerves.
> Bob
>> From: EB4APL <eb4apl at cembreros.jazztel.es>
>>To: time-nuts at febo.com
>>Sent: Sunday, March 23, 2014 7:35 PM
>>Subject: Re: [time-nuts] Nav Receiver Sawtooth Correction?
>>The sawtooth is generated by the granularity of the GPS receiver clock
>>not being synchronous with the recovered PPS.  The receiver program can
>>calculate the correction to be applied to the next PPS and outputs it in
>>a message, bu only in timing receivers, this is not a useful thing in
>>navigation receivers and I think that it cannot be calculated using the
>>satellites' position, it is a receiver "defect".
>>Why don't you buy a timing receiver?  An used Motorola Encore M12+
>>timing receiver can be bought by $35 or less (ebay items 290656401551 or
>>301131583613.  The seller is a known Time Nuts supplier).  An UT+ or GT+
>>even for quite less.
>>Ignacio EB4APL
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Chris Albertson
Redondo Beach, California

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