Re: NIST NTP servers

[Mel Beckman <mel () beckman org>]

The WWV signal is still accurate within a few milliseconds. Light is fast. Really fast.

 -mel

> On May 12, 2016, at 10:19 AM, Jean-Francois Mezei <jfmezei_nanog () vaxination ca> wrote:
>
> On 2016-05-11 10:30, Mel Beckman wrote:
>
> > Read deeper into the thread and you'll find where I sourced inexpensive RF-based NTP servers using CDMA, GSM, and 
> > even WWV. 
>
> For shortwave, you would need to calculate propagation delay between
> transmitter and receiver. (does signal reach via line of sight, bounce
> against ionosphere ?).
>
> Since CDMA is dead outside the USA and drying in USA, I wouldn't rely on
> that.  If GSM towers rely on a GPS receiver on the tower and those
> towers are near enough to your location (< 30km), then chances are that
> blocked GPS signals at your location would also jam the signals at the
> GSM antenna.
>
> And if you are setup to be totally autonomous in case of power failures,
> you need to know whether the GSM antenna you are relying on is also on
> permanent power backup or only has autonomy of a few hours.