[time-nuts] More ES100 WWVB Measurements

Tue Jan 1 01:47:56 UTC 2019

> If you are fairly deep inside a building, GPS isn’t going to get there.
WWVB likely
> will make it to an internal location.

Interesting thought. I wonder if anyone has tested WWVB reception in a
deep underground location such as a sub sub level in a building or parking
garage?

Wayne

On Mon, Dec 31, 2018 at 5:29 PM Bob kb8tq <kb8tq at n1k.org> wrote:

> Hi
>
> If you are fairly deep inside a building, GPS isn’t going to get there.
> WWVB likely
> will make it to an internal location.
>
> If you are convinced that WWVB is un-jamable and that GPS is easily
> jammed, WWVB
> would be more robust.
>
> That’s about it.
>
> Bob
>
> > On Dec 31, 2018, at 7:56 PM, Wayne Holder <wayne.holder at gmail.com>
> wrote:
> >
> > While reading this thread and pondering whether to buy and fool around
> with
> > an ES100-based module from Universal Solder, I suddenly found myself
> > wondering if there was any advantage to using the time received from WWVB
> > vs just using an inexpensive GPS receiver.  The ES100  module costs about
> > $70, but I can get a GPS receiver, with antenna, for far less than that
> and
> > I've had no trouble receiving GPS signals indoors with most modern
> receiver
> > modules.
> >
> > I suppose the low power requirements of the ES100 might be an advantage
> > when building battery powered clocks to mount on the wall, but it seems
> > like some of the newer, ultra low power GPS modules intended for use in
> > smart watches could also work in a battery-powered wall clock, especially
> > if the receiver was only powered on a few times a day to update the time.
> >
> > And, finally, if GPS modules are (or will some become) a suitable
> > replacement for WWVB receiver modules, do we really need WWVB in the
> modern
> > age?  Perhaps there's some critical advantage to using WWVB to get the
> time
> > but, offhand, I cannot think of it.  What am I missing?
> >
> > Wayne
> >
> > On Mon, Dec 31, 2018 at 4:30 PM Brooke Clarke <brooke at pacific.net>
> wrote:
> >
> >> 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-request at 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" <tvb at LeapSecond.com>
> >>>> To: "Discussion of precise time and frequency measurement"
> >>>>     <time-nuts at lists.febo.com>
> >>>> Subject: Re: [time-nuts] More ES100 WWVB Measurements
> >>>> Message-ID: <96BB388753294278A9CDE96C1EA7D9AE at 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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> >>
> >>
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