Hi Joseph:
Thanks for the patent link. I've added it to my WWVB phase modulation info at:
https://prc68.com/I/Loop.shtml#La_Crosse_UltrAtomic
--
Have Fun,
Brooke Clarke
https://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
axioms:
1. The extent to which you can fix or improve something will be limited by how
well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
-------- Original Message --------
On Mon, 31 Dec 2018 12:00:02 -0500, time-nuts-requ...@lists.febo.com
wrote:
time-nuts Digest, Vol 173, Issue 44
Message: 7
Date: Mon, 31 Dec 2018 04:04:22 -0800
From: "Tom Van Baak" <t...@leapsecond.com>
To: "Discussion of precise time and frequency measurement"
<time-nuts@lists.febo.com>
Subject: Re: [time-nuts] More ES100 WWVB Measurements
Message-ID: <96BB388753294278A9CDE96C1EA7D9AE@pc52>
Content-Type: text/plain; charset="UTF-8"
Hi Graham,
That's very nice work. And you have uncovered several unusual effects
in the ES100. Bugs? Features? If we time nuts keep up the good work
to evaluate this chip, we are likely at some point to get an
informative response from the guys who designed it. They read
time-nuts.
I didn't see this mentioned, but I think I have found the relevant US
patent application: US20130051184A1, Real-time clock integrated circuit
with time code receiver, method of operation thereof and devices
incorporating the same, Oren Eliezer et al, Oren Eliezer et al, filed
2013-02-28.
.<https://patents.google.com/patent/US20130051184>
Found this by chasing stuff from the EverSet website:
.<http://everset-tech.com/wp-content/uploads/2014/11/ReceiverRadioClocks.pdf>.
Joe Gwinn
So now both you and Tim have observed the off-by-one-second (or
off-by-N-seconds) effect in the ES100. I wonder if this explains why
some of my ES100-based La Crosse 1235UA Ultratomic wall clocks are
off by a second sometimes.
My main question: in your "Time Plot.PNG" plot, what is the cause of
the sawtooth pattern? The points are almost all on a clear negative
slope, though bounded by roughly +/- 75ms. Looking on the far left, I
see a time drift of +50 ms to -25 ms over an hour, which is
equivalent to a -20 ppm frequency offset; about -2 seconds/day.
Do you think this is due to the 16 MHz onboard xtal? If so, how about
changing the temperature of the eval board by a lot (say, several
tens of degrees) for an extended time (say, 4 hours) and see if the
sawtooth slope changes convincingly.
Also, just to be sure, can you put a known independent timing signal
(e.g., GPS/1PPS) into your complex BeagleBone Black / Debian 9.4 /
ntpd time server / Python 3 / Excel stack to establish the validity
of your measurement methodology? Very likely you did it right, but I
always cringe when I hear "Linux" or "NTP" and "precise time" in the
same sentence. Yes, sorry, forgive me; I grew up in the "trust, but
verify" generation [1]. It applies pretty well to metrology also ;-)
/tvb
[1] https://en.wikipedia.org/wiki/Trust,_but_verify
End of time-nuts Digest, Vol 173, Issue 44
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