Time Standard Dilemma

Due to the recent time change, I went about to adjust all of the clocks in my house, digital and analog. This past summer, I had purchased a new wristwatch, a Citizen Eco-Drive powered by light. I had set this watch by the clock on my GPS.

When it came time to set my clocks, I rechecked my wrist watch against a recently acquired "atomic clock" which is set by radio waves from NIST. They differed by about 15 seconds. Hmmm, wrist watch must has slowed down. For chuckles, I checked against the GPS. No, it was accurate.

I then compared the GPS clock to the "atomic clock" and found the 15 second difference. And as far as I can tell, it is exactly 15 seconds. repeated attempts to resynchronize the "atomic clock" to the NIST standard always results in a 15 sec. difference.

OK, I bet the "atomic clock" is the culprit for three reasons:

1: The GPS clock agrees with the local broadcast beef from the radio station

2: The GPS cost about 20 times the "atomic clock."

3: The GPS clock agrees with the computer clock which is also synchronized by the internet.

Could it be that the circuity in the "atomic clock" takes 15 seconds to adjust the output? If so, why not compensate for this?

Any ideas?

Al

PS:

In article , Al wrote: [... GPS vs "atomic clock" ..]

The GPS time reported from a real GPS will always be a little late. The time is the time of the fix and the fix happened at the edge of the 1PPS pulse. The actual message data is sent after it is calculated and is thus just a little late.

What I suggest happened: An "Atomic clock" must make some sort of calculations internally to determine the time. It would be reasonable for the very slow processor involved to take. lets say, 7.5 seconds to do this computation. The designers then "corrected for this" by adding a 7.5 Second delay. Since all the devices showed exactly the same time, the PHB thought they were also accurate and cut off the funding for all further testing and development.

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kensmith@rahul.net   forging knowledge

I read in sci.electronics.design that Al wrote (in ) about 'Time Standard Dilemma', on Mon, 4 Apr 2005:

You clock is tuned to a special NIST transmission intended for clocks on a CIA space station 2.79 million miles out.

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Hello Al,

Whenever I compared my "atomic clock" against WWVH on shortwave it was always accurate.

Regards, Joerg

Check it against your GPS. I know my GPS agrees with the local radio station "beeps" on the hour almost exactly.

Al

Hello Al,

I don't have a GPS. However, the WWVB clock also agrees with the stations, at least around Sacramento.

Regards, Joerg

You could be seeing the difference between GPS time and UTC time. It has to do with GPS's inability to adjust for leap seconds. Here is a link that explains this.

You dont listen to digital radio then!

martin

Opinions are like assholes -- everyone has one

At least two of my local radio stations are 15 seconds off at the beep because they use a delay to seamlessly remove coughing.

Could you give us the brand and model of your "recently acquired 'atomic clock'"?

I can see it now: radio station hacks their clock to GPS. If so, of course they'd agree.

The present GPS-UTC delta is 13 seconds (I have a time server at work that displays the difference).

Probably irrelevant to this thread, but in fact most PPS-output GPS timing receivers send the time string before the 1 PPS pulse.

I'm sure Garmin's with NMEA do this in some other randomly wrong way.

Tim.

Snicker ;-)

However, being an "analog geezer" doesn't necessarily mean everything is best as analog...

My wife talked me into buying a _beautiful_ Omega watch ($2400) that is self-winding. It won't stay ticking for more than about 12 hours, if you're not an arm waver.

So I wear my $20 Timex Indiglo Digital... and it keeps perfect time ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
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I love to cook with wine.      Sometimes I even put it in the food.

The difference between the time used internally by the GPS system and UTC is 13 seconds, but that difference and/or the correct UTC time is included in the data sent by the satellites, so that GPS receivers can display UTC.

--
Peter Bennett VE7CEI 
email: peterbb4 (at) interchange.ubc.ca        
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html 
Newsgroup new user info: http://vancouver-webpages.com/nnq

Ah, you must be one of those new-fangled digital-type guys who think that real men need 8-digit alarm clocks... We analog geezers would just rotate the second hand by 90 degrees.

Cheers,

Phil Hobbs

If it ain't free, I don't bother.

Al

OK, these are the most reasonable explanations. But then, what is legal time for court cases? 15 secs., or so, may not be much, but at 60 miles an hour it is.

Al

I just checked the clock and it has no brand name. Hmmm. It was made in China and sold at Walgreens for about $10 US. Aside from the 15 sec. or so discrepancy, it works just great. All it says on it is, "Atomic Clock." And I have seen it synchronize.

Could this be a plot to screw with our minds ;-)

Al

This is one "digital-type" that doesn't need no steenkin' alarm clock (haven't worn a watch in 20 years either). I only set an alarm when my schedule changes drastically (like to catch a 5AM flight) and even then I wake up before it goes off 9/10 times. Oh, and I never set the bedroom clock to back standard time. Damned Chineese-digital-types don't seem to understand the 'U' in UI.

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  Keith