[ntp:questions] Stick to PPS, even if the prefer server fails

John Ackermann N8UR jra at febo.com
Fri Mar 27 21:56:16 UTC 2009


David Mills said the following on 03/27/2009 05:44 PM:

> To John: I suspect you know that all LORSTA stations run by the Coast 
> Guard include in the weekly announcement series a time-of-coincidence 
> (TOC) second at which the epoch of the second is equal to the epoch of 
> the GRI. My Astron LORAN-C receiver, which was modified by the Coast 
> Guard, flashes a light at the TOC. The TOCs and the intervals between 
> them vary up to several minutes depending on the GRI of the chain. I 
> made provisions for the TOC in the LORAN-C receiver I built some years 
> ago, but never completed the code to exploit them.

Hi Dave --

Yes, the TOC can be used to generate an on-time PPS.  The Austron 2100 
(sometimes referred to as the "T" model) receiver has that capability 
(the more common 2100F version does not; it is useful only for frequency 
comparisons).

I drive one of my NTP servers (a modified Soekris SBC running nanoBSD) 
tied to the Austron 2100, and its crystal oscillator is locked to an 
Austron 2010B disciplined oscillator that is driven from the LORAN 
receiver.  I suspect that this may be the only LORAN-based NTP system 
running anywhere today.  It keeps very good time; in fact, its noise is 
comparable to a similar Soekris box that gets its PPS and oscillator 
from a Z3801A GPSDO.

Of course, the Coast Guard just announced that they plan to turn the US 
LORSTAs off in 2010 as part of budget cuts.  I don't know if that is 
political maneuvering to get a bigger piece of the pie, or a done deal.

John



More information about the questions mailing list