[time-nuts] ES100 BPSK WWVB jitter data

[Dana Whitlow]

Thanks, Tim, for the info on an interesting device.

BTW, has anybody yet heard definite news on whether or not WWVB will still
be
operating much longer?

Dana


On Tue, Dec 25, 2018 at 8:26 AM Tim Shoppa <tshoppa at gmail.com> wrote:

> I let the Universal Solder ES100 board run overnight in my basement in
> Maryland for 10 hours, its little loopsticks at least 5 feet from switching
> power supplies, and it often could get successful WWVB BPSK decodes.
>
> This is a feat in itself. No non-BPSK WWVB clock antenna has ever produced
> a useful  antenna has ever decoded anything in my basement before.
>
> It was connected to an Arduino Nano, which had its own internal
> crystal-derived millisecond clock. (Actually a cheapo $3 Nano clone. I love
> these cheapo Nano clones. They are to me, like 555's or 2N2222's.)
>
> The IRQ out of the ES100 is supposed to be good to +/-100ms of the second
> edge.
>
> I had it do a new acquisition cycle continuously overnight (around 2
> minutes per attempt). At the end of every acquisition attempt it printed
> the Arduino's millisecond clock timestamp of the IRQ, success or not. And
> when it was an acquisition success,  it also printed the UTC decoded. The
> Arduino code is in the zip file and is called 'es100_arduino2.c'. It is
> just a slight tweak on the Arduino code supplied by Universal Solder.
>
> The Arduino was connected to a PC that logged the Arduino's serial data.
> The serial data is in the zip file called 'es100.txt'.
>
> A perl program 'anal.pl' reads the serial data and produces two column
> data, output to 'plot.out'.
>
> Over the 10 hours, there were 142 successful ES100 acquisitions of WWVB  in
> 281 attempts.
>
> What I did, is for each successful acquisition, plotted the millisecond
> clock (x axis) vs the millisecond clock minus UTC seconds*1000 (y axis)
>
> I am attaching the Arduino sketch, the serial data produced, a perl program
> that analyzes the raw data (and subtracts UTC seconds*1000), and two
> graphs.
>
> You can see in 'drift.pdf', that over the 10 hours, the Ardunio's
> millisecond clock drifted by about 2.8 seconds. So  the offset of the
> Arduino's crystal clock seems to be 78 ppm.
>
> You can also see the scatter in the residual, in graph 'jitter.pdf',
> showing the ES100's jitter on the IRQ second edge. Only twice did it go
> just a little beyond the spec sheets +/-100ms specification and usually was
> less than +/-50ms.
>
> I don't see any sawtooth or other weird stuff going on in the residual.
>
> Tin N3QE
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