[time-nuts] Another "atomic" clock question

Sun Mar 2 05:01:04 UTC 2014

Here's a little anecdote that tells how far we have come in the last 50 
years.  I had the privilege of visiting a NASA lab in 64 I think it was. 
They showed us, I was with a student group, a setup with a scope a WWV 
receiver and a rotating transformer that would change the time on a clock 
one millisecond for every turn of a crank.  The seconds output from the 
divider chain triggered a scope sweep and the vertical displayed the audio 
from WWV.  The guy could turn the crank and position the start of the time 
tick on the left of the screen.  Then he turned the crank to correct for 
light time delay.  I think WWV was still in Maryland at that time.  I don't 
remember exactly when they moved it to Colorado.  Anyway, this was the 
master clock for tracking and telemetry for the manned space flights of that 
time.

Regards.

Max.  K 4 O DS.

Email: max at maxsmusicplace.com

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----- Original Message ----- 
From: "paul swed" <paulswedb at gmail.com>
To: "Bob Albert" <bob91343 at yahoo.com>; "Discussion of precise time and 
frequency measurement" <time-nuts at febo.com>
Sent: Saturday, March 01, 2014 8:33 PM
Subject: Re: [time-nuts] Another "atomic" clock question

> Careful where you step. You may just get sucked into time nuts and it 
> never
> stops.
> Get a good crystal, then its an RB, next you know your paying shipping for
> a 100 Lbs Cesium. Evil stuff.
> Or you can just skip all the distractions and get a good GPSDO.
> Not as much fun learning on the way. But depends on your end goal.
> Regards
> Paul
> WB8TSL
>
>
> On Sat, Mar 1, 2014 at 9:04 PM, Bob Albert <bob91343 at yahoo.com> wrote:
>
>> All this is very interesting.  However, my interest is frequency.  In
>> other words, I want to know that my standard oscillators are as close to
>> desired frequency as possible, and how close that turns out to be.
>>
>>
>> Yes, the Internet gives me time of day as close as I care to know.  I 
>> have
>> an 'atomic' clock from LaCrosse that resets itself nightly, although it's
>> fussy about where in the house I put it.  If I put it where I'd like, it
>> won't receive WWVB, so I put it across the room.  I called the company
>> inquiring about augmenting the internal antenna but they were of no help.
>>
>>
>> While watching the clock and listening to WWV, it seems the clock is a
>> fraction of a second behind.  Even that doesn't matter, but calibrating 
>> the
>> counter time base is another kind of thing.
>>
>> I am trying to understand how this is done.  Should I ever get a rubidium
>> standard, I'd want to check its calibration, and that's not a trivial
>> exercise.
>>
>> Bob
>>
>>
>>
>>
>> On Saturday, March 1, 2014 4:56 PM, Paul Alfille <paul.alfille at gmail.com>
>> wrote:
>>
>> There are WWVB clocks with serial output. Arcron made one that I added
>> linux ntp support for some years back.
>> http://www.atomictimeclock.com/radsynarcron.htm
>>
>> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver27.html
>>
>> As I recall, it was under $100, quite nicely styled, and is sitting here 
>> on
>> my desk. (Reception on the East Coast can be spotty, so I've switched to
>> standard internet net time source).
>>
>>
>>
>>
>>
>>
>> On Mon, Feb 24, 2014 at 7:44 AM, Bob Camp <lists at rtty.us> wrote:
>>
>> > Hi
>> >
>> > Ok, so 0.1 second at the sync point is indeed a reasonable estimate. If
>> > that's all you need to deal with (you correct out the crystal offset 
>> > one
>> > way or the other) then:
>> >
>> > At 1 day you have 11.5 ppm accuracy. Roughly a 100 Hz beat note with 
>> > WWV
>> > at 10 MHz.
>> >
>> > At 10 days you have 1.15 ppm. Roughly a 1 Hz beat note at 10 MHz.
>> >
>> > At 100 days you have 0.115 ppm. That would be about a 10 second period
>> > beat note.
>> >
>> > None of that is to say that a beat note is all there is to getting
>> > accuracy off of WWV or that the two approaches deliver the same net
>> > accuracy. Yes I've done the 10 second beat thing, it can be done with
>> care
>> > and a good stable WWV signal.
>> >
>> > Bob
>> >
>> > On Feb 23, 2014, at 5:21 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
>> >
>> > >> Now that you have brought up this subject, do you know of any way to
>> > use these LaCrosse clocks to calibrate frequency standards?
>> > >
>> > > I suggest using a direct electric (1.5 VDC high-Z) or indirect 
>> > > magnetic
>> > (high gain) pickup on the coil to get the +/- pulse per second. Compare
>> > this time with your local frequency standard and over several days you
>> > should get accuracy better than 10 ms per day (1e-7). Here's an example
>> of
>> > a raw phase plot:
>> > > http://leapsecond.com/pages/Junghans/
>> > >
>> > > /tvb
>> > >
>> > > _______________________________________________
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