Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!gatech!emory!stiatl!john
From: john@stiatl.UUCP (John DeArmond)
Newsgroups: sci.electronics
Subject: Re: NBS time broadcast
Message-ID: <6142@stiatl.UUCP>
Date: 28 Jul 89 03:43:17 GMT
References: <8720@kean.mun.ca>
Reply-To: john@stiatl.UUCP (John DeArmond)
Organization: Sales Technologies Inc., "The Procedure IS the product"
Lines: 36

In article <8720@kean.mun.ca> andrew@kean.mun.ca writes:
>Now, a few years ago, I remember seeing a Heathkit (read:expensive) project for 
>"the world's most accurate clock".  Apparantly the thing picked up a broadcast 
>from the NBS and decoded it.
>
>So the question... anyone know how this works and how/where it is broadcast?
>
Someone else can probably comment on the nitty-gritty of the time code
protocol.  Since I own one of the Heathkit clocks (40 bux at a H-K surplus
sale :-), I can comment on its use from a user perspective.  

The time code is encoded on the audio of all WWV & WWVH broadcasts.  It is
(i think) a component of the tick audio.  The heathkit clock scans the 5,
10, & 15 mhz frequencies and picks the best.  The clock has a "data" led
that indicates when it is receiving valid data.  There is also an LED to
indicate "super accurate" mode.  That is, the clock is synchronized 
with the broadcast.  Even in the absence of a broadcast, the clock 
continues to run but not to specification.

The clock displays one-hundreths of seconds.  IT also has an RS-232 
port that outputs the time in ascii each second.  Funny, the output is
not synchronized to the time code.  The clock has dip switches on
the bottom for setting propagation delay compensation.  Since I don't
know know how to calculate this, not having gotten a manual, I just set
it to midway and forget it.  

The receiver in the Heath unit is very poor.  I had to erect a large
dipole to get a signal under any condition.  Even with this antenna,
I cannot receive the signal if a computer is on in the shack.

If you find one of these clocks surplus, it is a pretty good deal.
It IS nice to have The Time at all times.
-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
Sales Technologies, Inc.    Atlanta, GA    | This is Unix, My son, You 
...!gatech!stiatl!john    **I am the NRA** | just GOTTA Know!!!