[time-nuts] n00b contribution -- WWVB software for EVERSET ES100 dual-antenna receiver

[Fiorenzo Cattaneo]

Hello everyone, this is the first time I actually make a modest n00b
contribution to time-nuts, so please be kind with me 😊 I will appreciate
any comments, criticism and suggestions.



Aside from GPSDO and Rubidium Oscillators, I am also quite interested in
radio clock receivers. So I found the EVERSET ES100 WWVB receiver on
Amazon, ordered it, and wrote some code for it. I’ve only had this for a
couple days, barely enough time to hack together a few lines of python code
which I use as a test program. Once I work out all the kinks and add all
the functionality I think is needed, I’ll then go ahead and write an SHM
based refclock for NTP, in C code of course.



GITHUB link: https://github.com/fiorenzo1963/es100-wwvb-refclock



I hope it’s okay to post partial work (in the spirt of open source “release
early, release often”.

The receiver is fairly inexpensive, and I’m using a Raspberry PI 3 which I
had lying around. I’ve only had this running for a few hours, so I can only
show every preliminary data. Phase error is measured against the local
oscillator, disciplined via NTP against 3 local GPSDO servers.

I’ve oriented the dual antennas at 45 degrees of each other, with their
intersection roughly pointing to Fort Collins.



First results:

   - These logs have been taken from 2019-11-15T11:09:18Z to
   2019-11-15T22:35:49Z
   - RX statistics indicate a successful RX rate of 44%

        RX_OK_ANT1          1      /* RX count on ANT_1 */

        RX_OK_ANT2        113      /* RX count on ANT_2 */

        IRQ_NO_DATA       145      /* RX unsuccessful, WWVB retrying
(currently simply timed-out) */



   - Phase (aka offset) error statistics compared against a local
   GPS-disciplined stratum-1 clock
      - Average ~ -10 milliseconds
      - Most samples are within +40/-60 milliseconds
      - All samples are within +60/-120 milliseconds
   - Phase (aka offset) error plot, with moving average (note that RX
   errors are ignored here) [image: alt text]
   
<https://raw.githubusercontent.com/fiorenzo1963/es100-wwvb-refclock/master/images/wwvb_offset_error_20191115.jpg>



Hope you enjoy,

Cheers,



-- Fio Cattaneo



Universal AC, can Entropy be reversed? -- "THERE IS AS YET INSUFFICIENT
DATA FOR A MEANINGFUL ANSWER."

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