Hi Bob,
So, to use this as a phase reference for testing my unit, I'd have to get the
phase error out each second and correct for that? Or is it a matter of the
OCXO getting happy over the next few weeks and it will settle down? In my
mind's eye, I see its DAC moving on a slope just like mine is, as the OCXO ages
in.
It looks like I need to put a shelf on the wall and give this a permanent home.
At the very least, that would get it out of my way so I can do other work.
All things considered, it's a good problem to have. =)
Bob
From: Bob Camp <[email protected]>
To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
measurement <[email protected]>
Sent: Saturday, October 25, 2014 11:12 AM
Subject: Re: [time-nuts] Lucent KS-24361/Z3812A GPSDO initial setup
Hi
If the Z3810/11/12 is like the other HP / Symmetricom boxes (and I’d bet it is):
1) It will go into survey and sync relatively slowly compared to some of the
other units.
2) It’s got a less sensitive / lower channel count receiver than stuff like
Said’s new part.
3) It will take a *long* time to get to it’s best stability operating point.
Think weeks / months not hours.
4) It has pretty good environmental rejection. You won’t see much (as in any)
benefit in a normal basement / always locked installation.
5) It’s phase noise isn’t as good as some units. (like a TBolt )
6) Lady Heather does not play well with one :(
My guess is that the Z3805 has pretty much the same “stuff” in it. They both
come from the same era and (may) have the same MTI OCXO in them.
Bob
> On Oct 25, 2014, at 11:24 AM, Bob Stewart <[email protected]> wrote:
>
> Hi Bob,
>
> During the first hour it reported poor geometry a number of times. Then it
> seemed to get its act together and was solidly into survey mode. A few hours
> later and it was satisfied with life and went into hold mode, with TFOM=3,
> FFOM=0.
>
> This morning, I see that there is some phase tracking difference of opinion
> between my GPSDO and this one WRT the 10MHz signal out from REF-0.
>
> http://evoria.net/AE6RV/GPSDOe/Z3812A.10.25.png
>
> The green is the phase difference plot, and the red is the ADEV. Given this
> is the first time I have done this against another GPSDO, I don't know
> whether this is good or bad. Looking at the phase plot on my unit, it
> wanders around a bit but not 100ns.
>
> http://evoria.net/AE6RV/GPSDOe/GPSDO.10.25.png
>
> Sorry the plot is so busy with debug traces. You can easily spot the same
> phase difference line as in the one above. The blue squiggle is my phase
> error. The red is my DAC. The phase in this plot is in hundreds of ps. I
> have shut the unit down numerous times recently, and the OXCO has been
> subjected to different thermal environments. Right now the case is closed,
> there are no vent holes, and the temperature in the box on my PCB is just a
> bit over 99 degrees F.
>
> Bob
>
> From: Bob Camp <[email protected]>
> To: Bob Stewart <[email protected]>; Discussion of precise time and frequency
> measurement <[email protected]>
> Sent: Saturday, October 25, 2014 7:09 AM
> Subject: Re: [time-nuts] Lucent KS-24361/Z3812A GPSDO initial setup
>
> Hi
>
> One of the interesting things about these little receiver modules is that
> they don’t all report the same survey location. There are NIST papers with
> examples. You could probably spend a lot of time on the “why”.
>
> If you are getting “poor geometry” errors, either you have an antenna issue,
> or your receiver is in trouble some other way. It should go into survey mode
> and stick there. It should be solidly into the survey after about 10 minutes
> power on.
>
> Bob
>
>
>
> > On Oct 24, 2014, at 9:46 PM, Bob Stewart <[email protected]> wrote:
> >
> > Sorry if these comments are a bit naive, but this is my first exposure to a
> > Z38xx.
> >
> > I've got mine powered on and connected to the antenna. After referring to
> > Stewart's original post (once again) I've managed to download HP's SATSTAT
> > and get it running. When I connected to the REF-1 unit (with the receiver)
> > all I get is comms errors. But when I connect to REF-0, Satstat seems
> > quite happy. It's reporting the unit as a Z3812A. Is REF-0 the only one
> > you can connect to, or is REF-1 mute till it's happy with the GPS receiver?
> >
> > The mode says "Power-Up: GPS Acquisition", so I guess that's OK. I think
> > things are progressing. It's attempting to survey, but reporting
> > "Suspended: poor geometry". I suppose with a little more time this will
> > work itself out? It seems to be slowly tracking more sats, as it's now up
> > to 5.
> > I wonder if there's a way to shortcut the survey process using Satstat?
> > I've got a 48 hour survey done on this antenna with the LEA-6T, so I should
> > be able to input those figures, right? I'll see if I can find anything in
> > a Satstat manual I found.
> >
> > Bob - AE6RV
> >
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>
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