[time-nuts] Strange event on my Z3805A [REVISED to correct links]

Steve Rooke sar10538 at gmail.com
Tue Feb 2 09:12:43 UTC 2010


Matt,

It's not easy to see but if you look at the 72h plot, you can see that
the EFC voltage stops at a low value before the event and then
continues at a higher voltage after it. Look at the EFC level values
before and after.

This is the first time I've seen anything of the magnitude on the
Z3805A in almost a year. As you can see from the graph showing the 36h
prior to the event, there are many changes in the number of sats and
there would be many changes of different sats that are tracked over
that period but without any events like this. You can see a lot of
spikes in the TI graph indicating the switching of the sats. This is
the magnitude I expect to see but when you compare those spikes on the
72h graph you can see that this is a very very large and inexplicable
event.

Steve

On 2 February 2010 16:58, Matt Osborn <kc0ukk at msosborn.com> wrote:
> Steve,
>
> I'm much more wizened than wise, but my understanding is that crystal
> jumps do not come back. They stay at their new frequency.  I did
> notice on your graph of the event that there were changes in the sat.
> constellation at the beginning and end of the anomaly.
>
> I've seen similar moves on both my Thunderbolt and Fury GPSDOs. All
> seem to be related to satellite switching. One was so repetitive I was
> able to identify the offending satellite.
>
> On Tue, 2 Feb 2010 15:00:50 +1300, Steve Rooke <sar10538 at gmail.com>
> wrote:
>
>>On 2 February 2010 11:11, Matt Osborn <kc0ukk at msosborn.com> wrote:
>>> I've seen similar results when the receiver switches satellites.
>>> Multipath??
>>
>>It does that all the time as sats come in and out of view but I've
>>never seen an event of this magnitude before. If you look at the trace
>>for the preceeding 36h you can see peaks where the unit switches stats
>>but those peaks are decades less than this peak.
>>
>>I also see that the EFC voltage changes very significantly, is this
>>perhaps one of the infamous crystal jumps we have spoken about I
>>wonder. The area of interest is that it appears somewhat unstable
>>after the event but is improving now.
>>
>>Multipath, I don't think so as nothing has changed here and I live in
>>an urban area well outside the city. Nothing has been errected or
>>changed as far as I can see.
>>
>>Cheers,
>>Steve
>
> -- kc0ukk at msosborn dot com
>
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-- 
Steve Rooke - ZL3TUV & G8KVD
A man with one clock knows what time it is;
A man with two clocks is never quite sure.




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