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[time-freq] Re: Febo.com's Z3801A Performance

John Ackermann N8UR jra at febo.com
Sat Jun 30 11:26:51 UTC 2007


Gregg Levine said the following on 06/29/2007 10:40 PM:

> Hello!
> John can you, ah, point out as to which unit the Z3801A system is?
> Consider this folks, LORAN C is a form of radio, it was originally
> created for the maritime trade for such issues as distance tracking of
> ships and points on land. .

It happens I just updated my plotting software yesterday to add
reference tags to the plot legends, so the graphs now show which unit is
which.  But just in case, tick is LORAN-C, tock is Z3801A, and toe is WWVB.

> Isn't it possible that the LORAN C reception is being effected by
> Jansky noise? What we consider to be static on those areas of the
> radio spectrum that are not allocated could be that form of noise. It
> could also be all sorts of everything else. However I shall leave out
> the areas of reference that are straight out of science fiction for
> this area of discussion.

I'm tracking a LORAN station that is reasonably close to me (175 miles
away), so the signal is pretty strong.  And, since the receiver is
locking to a zero crossing and measuring time difference between arrival
of pulses, I don't think that moderate interference would affect the
results, though enough interference could cause the receiver to lose lock.

> Side trip back towards my first post and your responses, (because I
> first saw what you replied to on this, John, as part of a digest with
> them.): I have since found the PPS Kit for Linux on the kernel.org
> site. I've built a kernel with the stuff applied. The next step is to
> setup my hardware for those tests, and then work out how to generate
> my graphs. John what methods did you use for that purpose?

I need to package up the tools that I'm using and post them; I'll try to
do that this weekend.  But in short, I grab the standard ntp clockstats
file and run a perl script over it to extract the offset and jitter
data, separated by clock source.  That data is then plotted
automagically using the Grace plotting tool (available only for *nix,
unfortunately).  A set of shell scripts kick off the program for daily,
weekly, and long term plots.

John





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