[GPS_Standard] GPSstd_PLL - today's plot of SM1/SM2 at about 53 hours in

[Bob Stewart]

Hi Chris,

Ah, sorry about the numbering.  The span between +10 and -10 is 360 degrees of phase.  As this test has progressed, it looks like my best guess of 0 degrees is off by a bunch.  And I think the plot would be more useful if 180 degrees was in the center, anyway.  But, the other plots are using the same rotation, so it's a bit late to change it and still be able to compare them.  I'm kind of stuck with it.  And, unfortunately, when I finally power this down I plan to add a BNC socket to extract the 1PPS signal (It's just a piece of wire at the moment) so the delay will change again.  At least it will be stable after that.  Hey, I'm not an electrical engineer.  I'm learning most of this as I go.  =)

As far as the rapid excursions, those seem closely related to when I turn the thermostat down at night and when the sun comes out in the morning.  I hadn't noticed the connection till now.  My program does not do a very good job of managing thermal drift.  Dave and I tried a number of different things, but none were reliably better.  Thanks for pointing it out.   One of the reasons for posting these is to get the input from a few more eyes.

Bob




>________________________________
> From: Chris Howard w0ep <w0ep at w0ep.us>
>To: Bob Stewart <bob at evoria.net> 
>Sent: Thursday, November 14, 2013 2:05 PM
>Subject: Re: [GPS_Standard] GPSstd_PLL - today's plot of SM1/SM2 at about 53 hours in
> 
>
>
>Can you explain a bit more about what we are looking at?
>
>I think I understand DAC value (control voltage) being the top plot.
>What is the bottom plot?  Why does it go from -10 to 10?
>
>What do you think about the rapid excursions in the bottom plot
>appear to be all slanting downward?  I'm talking about
>near 00:00 11/13  06:00 11/13 and 00:00 11/14.
>The DAC doesn't seem to do that.  Any idea on that?
>
>
>Chris
>
>
>On 11/14/2013 1:10 PM, Bob Stewart wrote:
>> I left it running, as promised, and here is the link.  It seems to have settled down to an interesting pattern over the past 12 hours with no net phase crossings.  However, as there is nothing in the software to account for oscillator aging, this will eventually change and reach some new temporary equilibrium.
>> 
>> In looking at the plot, though, I only see 8 phase crossings once it reached stability at about 11:00 AM no November 12.  All things considered, that's quite good.  I've got a number of new ideas that I'd like to try, but I think I'll let this continue to run for awhile.  The temperature variation near the GPSDO over the past 24 hours has been between 73 and 79 degrees F.
>> 
>> http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/SM1SM2.53hrs.png
>> 
>> Bob - AE6RV
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