Re: opensource_gps Digest, Vol 37, Issue 2

Hello Ilir,

I used to work at Rockwell GPS in Newport Beach, CA with Larry Vittorni. He
likes to dig his teeth into technical issues  such as this.  On the
commercial side of GPS receivers, we developed a "S" curve for the
temperature effects for the particular crystal and oscillator being used and
stored that information in an eeprom.  We would establish our reference
point, based on the internal temperature sensor physically attached to the
crystal, at an operating temperature of 25 deg C.  By knowing the voltage
curve for the temperature sensor, we then knew where we were on the
crystal's "S" curve and could apply the propper correction to the
oscillator.

Most of the OSGPS work so far is at room temps (or whatever it is inside the
particular PC in use), so this may not be worth the additional hardware to
sense the temperature.  But as we all know, temperature is the biggest
contributor to crystal oscillator accuracy.  The other thing you can do is
add an external 10 MHz. oscillator such as a rubidium or cesium!  The
GPSBLDR2 board I make (see www.gpscreations.com) has provisions for such.

Regards,

Doug

-----Original Message-----
From: Ilir Progri [mailto:[email protected]]
Sent: Wednesday, November 22, 2006 12:59 PM
To: 'Doug Baker'; 'Clifford Kelley'; 'Mike Parker (Irv)';
[email protected]
Subject: RE: [OpenSource_GPS] opensource_gps Digest, Vol 37, Issue 2


Dear Doug,

Thank you also for the data sheet on the Rakon oscillator. It seems like a
great start.

Regards,
Ilir

-----Original Message-----
From: Doug Baker [mailto:[email protected]]
Sent: Tuesday, November 21, 2006 9:29 PM
To: Clifford Kelley; Mike Parker (Irv); Ilir Progri;
[email protected]
Subject: RE: [OpenSource_GPS] opensource_gps Digest, Vol 37, Issue 2

All,

Attached is a data sheet on the Rakon oscillator that I use.

Regards,

Doug

-----Original Message-----
From: Clifford Kelley [mailto:[email protected]]
Sent: Tuesday, November 21, 2006 6: PM
To: Mike Parker (Irv); Ilir Progri; [email protected]
Cc: Douglas Baker
Subject: Re: [OpenSource_GPS] opensource_gps Digest, Vol 37, Issue 2


Thanks,  I'll take a look at it.  Doug uses a Rakon oscillator although I'm
not sure
which part number it is.

Cliff

-----Original Message-----
>From: "Mike Parker (Irv)" <[email protected]>
>Sent: Nov 21, 2006 12:23 PM
>To: Ilir Progri <[email protected]>, [email protected]
>Subject: Re: [OpenSource_GPS] opensource_gps Digest, Vol 37, Issue 2
>
>Here is a white paper from Rakon describing typical TCXO
>Requirements for high sensitivity gps applications
>(acquisition and tracking).
>
>Might be useful?
>http://www.rakon.com/whitepaper_files/gpsworld_innovation_final_nov03.pd
>f
>
>Regards,
>
>Mike
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of Ilir
>Progri
>Sent: Tuesday, November 21, 2006 12:11 PM
>To: [email protected]
>Subject: Re: [OpenSource_GPS] opensource_gps Digest, Vol 37, Issue 2
>
>Do we have a statistical and system model for the clock? I believe that
>we
>have to make more studies for the statistical and system clock models
>which
>will explain some of the problems that you Cliff are having.
>
>Regards,
>Ilir
>
>-----Original Message-----
>From: [email protected]
>[mailto:[email protected]] On Behalf Of
>[email protected]
>Sent: Saturday, November 18, 2006 12:00 PM
>To: [email protected]
>Subject: opensource_gps Digest, Vol 37, Issue 2
>
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>   1. OSGPS CVS update (Clifford Kelley)
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>----------------------------------------------------------------------
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>Message: 1
>Date: Fri, 17 Nov 2006 21:30:10 -0800 (GMT-08:00)
>From: Clifford Kelley <[email protected]>
>Subject: [OpenSource_GPS] OSGPS CVS update
>To: [email protected]
>Message-ID:
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><18487525.1163827810860.JavaMail.root@elwamui-mouette.atl.sa.earthlink.n
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>Content-Type: text/plain; charset="UTF-8"
>
>I've just updated OSGPS to change the tracking state carrier loop back
>to 1
>ms update rate.  It was having trouble with cycle slips and I think the
>clock is not stable enough to coherently integrate over 20 ms.
>
>Best regards,
>
>Cliff
>
>
>
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