Path: utzoo!utgpu!watserv1!watmath!att!pacbell.com!ucsd!usc!elroy.jpl.nasa.gov!ncar!gatech!kd4nc!n4hgf!wht
From: wht@n4hgf.Mt-Park.GA.US (Warren Tucker)
Newsgroups: comp.sources.d
Subject: Re: Obtaining time info from Naval Observatory
Message-ID: <302@n4hgf.Mt-Park.GA.US>
Date: 22 Jan 91 20:59:52 GMT
References: <1991Jan09.003434.5379@esleng.uucp> <1991Jan11.040746.7981@alembic.acs.com> <1991Jan14.205634.2201@ux1.cso.uiuc.edu>
Reply-To: wht@n4hgf.Mt-Park.GA.US (Warren Tucker)
Organization: Amateur Radio Station N4HGF
Lines: 32

In article <1991Jan14.205634.2201@ux1.cso.uiuc.edu> mcdonald@aries.scs.uiuc.edu (Doug McDonald) writes:
>In article <1991Jan11.040746.7981@alembic.acs.com> csu@alembic.acs.com (Dave Mack) writes:
>>In article <1991Jan09.003434.5379@esleng.uucp> dag@esleng.uucp (David A. Gilmour) writes:
>>>I have seen references to a program which can automatically obtain
>>>the time from the Naval Observatory and update the system clock.
>>Warren Tucker's nbstime code is pretty specific to Xenix on a PC
>>clone. Here's what I hacked together using that as a starting point.
>However, how accurate is the time you get? That is, is there any
>way to tell what the propagation delay is, and also, exactly when in the

The time is *fairly* close +-10 seconds or so. The clock they keep
is supposed to be jam on (their budget is larger than i would charge
to keep a Casio sync'd to WWV every day or so :-)).  It usually is
quite right, but some reports have shown it to be off by 12 seconds
or so.  I imagine that if you call with a *direct*-attached modem
(no servers, local networking, or whatever) you'll get good time
most very time.

The propagation delay is not > 1 second over the phone network. It is
probably < 100 msec here in Atlanta.  That's good enough for me!
If I needed more accurate time, I would get one of the three-frequency
diversity HF receivers and wheel over my dual-trace oscilloscope
and match the ticks with my local cesium standard, subtracting, of
course the calculated propagation delay from Fort Collins. Total
investment -- I don't want to think about it.

The time hack is on the stop bit of the '*' (or thereabouts :-)).
 
-----------------------------------------------------------------------
Warren Tucker, March Hare   gatech!n4hgf!wht or wht@n4hgf.Mt-Park.GA.US
When bad men combine, the good must associate;  else they will fall one
by one, an unpitied sacrifice in a contemptible struggle. -Edmund Burke