Atomic Clocks and Aluminum Siding

[Earl W Cunningham]

Ron, AC7AC wrote:

"That means my $6 Radio Shack digital clock that I chose because it was
on sale and provides a 24-hour time format is  perfect. It stays accurate
to within one or two seconds a month."
==========
I guess I'm more of a perfectionist than Ron.  After three or four
battery-operated digital clocks that gained or lost one or two seconds a
month (resetting them was always a pain in the butt), I plunked down $12
at Wal-Mart for an Oregon-Scientific "atomic" clock that is always exact
whenever I check it against 10 MHz WWV.  It displays GMT date and time
(down to the second) and is the ideal clock for the ham shack.

It also works indoors in the ham shack, whereas my much more expensive
hand-held GPS (which also displays accurate local time) does not (those
microwaves don't go through anything opaque).

73, de Earl, K6SE
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[k6dgw]

> And, if anyone wants, I will send them a picture I took of two
> identical model atomic clocks, both showing that they are "locked"
> and showing different times (nothing doctored in the picture, time
> zones the same, etc.).

Hmmm...I wonder why they call them "Atomic Clocks?"  Other than being
made of atoms like everything else, there is nothing "atomic" about any
of them.  All the atomic things are in Ft. Collins, Hawaii, and on GPS
spaceships.  I think my clock (which I won at the radio club raffle)
syncs to WWVB on 60 KHz, which I can hear on the left-coast at night,
but not in the daytime.

I volunteer at the Blood Center, and since the FDA requires that they
keep a series of times for each of the various blood donation steps for
each donor, they got us three "Atomic Clocks," two Sony's and a Seiko,
so all the times would be consistent.  My job was to hang them on the
walls, and when they were laying together on the table, I noticed that
they all differed from each other by as much as 10 seconds.  I took in
my K2, and they all differed from WWV too.  So much for "atomic time,"
my Pulsar watch does better than that.

73,

Fred K6DGW
Auburn CA CM98lw

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[Tom Bosscher]

  Almost everything in life can be overdone, except for K2 Mojo. I have
GPS clocks at work that keep the PC's all agreeing with each other. But
I did want a Gee-Whiz factor for the shack. At Dayton last year I bought
my very first MFJ product, a Model 121 clock. This is a large Dual LCD
readout "atomic" clock. You set one display to local, the other to UTC.
And it shows hours, minutes and seconds. It's the best of all worlds.
And now that SBC has dropped the time lady, by wife (W8IIE and provider
of my K2), takes it off the wall and uses it to set all the "blinking"
clocks in the house.
   When it comes to time and accuracy, remember the saying " A man with
one clock knows the time. A man with two isn't sure".

                  tom bosscher K8TB

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[K0GU]

>>Anybody else on this reflector ever been to the WWV transmitter site? I was
>>there circa 1992.
>>    
>>

  I live two miles from WWV. I get accurate time on my atomic clock, my
telephone, my stereo, my TV...

--
73,  Jay  K0GU  DN70mq


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[Ron Lorenz]

ya, ya

as an old Cdn AF Nav plus an astro-physicist, I'll stick with WWV!

Ron VA6RL


----- Original Message -----
From: "Fred Jensen" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Sunday, January 09, 2005 4:28 PM
Subject: Re: [Elecraft] Atomic Clocks and Aluminum Siding

> > And, if anyone wants, I will send them a picture I took of two
> > identical model atomic clocks, both showing that they are "locked"
> > and showing different times (nothing doctored in the picture, time
> > zones the same, etc.).
>
> Hmmm...I wonder why they call them "Atomic Clocks?"  Other than being
> made of atoms like everything else, there is nothing "atomic" about any
> of them.  All the atomic things are in Ft. Collins, Hawaii, and on GPS
> spaceships.  I think my clock (which I won at the radio club raffle)
> syncs to WWVB on 60 KHz, which I can hear on the left-coast at night,
> but not in the daytime.
>
> I volunteer at the Blood Center, and since the FDA requires that they
> keep a series of times for each of the various blood donation steps for
> each donor, they got us three "Atomic Clocks," two Sony's and a Seiko,
> so all the times would be consistent.  My job was to hang them on the
> walls, and when they were laying together on the table, I noticed that
> they all differed from each other by as much as 10 seconds.  I took in
> my K2, and they all differed from WWV too.  So much for "atomic time,"
> my Pulsar watch does better than that.
>
> 73,
>
> Fred K6DGW
> Auburn CA CM98lw
>
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[Jack Brindle]

At 12:34 PM -0800 1/9/05, Ron D'Eau Claire wrote:

>I thought atomic clocks were desired for their "gee whiz" interest, not
>because someone usually needs to know what time it is to the nearest
>millisecond.


>I'm serious about the value of the "gee whiz" factor as in, "Gee whiz! Look
>at that!"
>
>After all, isn't that why we're all hams and why we build gear? Let's not
>insist on diluting the sheer enjoyment of the "Gee whiz" response with petty
>practicality...

Ron, I think you are missing it completely. We hams tend to be lazy.
We build things to make it easier for us.

In my case, I got really tired of my wife yelling at me because the
clocks were an hour off six months out of the year. Why some years it
got so bad that I actually considered resetting some of the clocks.
Then I found (and bought) some of these "atomic clocks." They are
on-time all year around, The YF doesn't miss her shows any more, and,
most important, they have eliminated the "atomic ache."

I just wish I had thought of creating the device before anyone else
had so that now _I_ would be rich and not the guy who actually did
it...

THAT's the "Gee whiz" factor, as in, "Gee whiz, why didn't I think of that..."

-Jack Brindle, W6FB
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[John Magliacane]

--- "Stephen W. Kercel" <[hidden email]> wrote:

> Dave:
>
>  From the 1 callsign, I expect that you are located in New England. If so,
> you're on the ragged edge of the normal coverage of WWVB. It is likely that
> the location is giving you as much trouble as the metal siding.

WWVB is by no means a "weak signal".  But like everything thing else in
radio, "It's the signal-to-noise ratio, stupid!"  :-)

Look for local noise sources.  Much like an AM radio, "atomic clocks" use a
ferrite loopstick antenna for reception.  The tiny receivers in them have a
sensitivity is on order of 0.5 uV.  A tuning fork crystal provides
selectivity on the order of 10 Hz.

A loopstick antenna responds primarily to the magnetic component of
electromagnetic waves.  Since magnetic fields follow an inverse cube
(rather than inverse square) law, if you've got an interference
problem with a magnetic probe antenna, the source is likey right under
your nose.

Keep your clock as far away from (and at right angles to) gadgets in your
home that might use switch-mode power supplies (EVEN if they are turned off!).
Our Sylvania color TV set is a prime generator of LF hash at my QTH, even
when the TV is off.  It took me a year and a half to discover this -- by
accident!

Also, the 5th harmonic of any TV's horizontal oscillator is only a few
kHz from 60 kHz.  Computer monitors sometimes cause problems as well.
I've heard that some UPS units use a switched-mode power supply operating
at 60 kHz.  (Manufacturers have discovered the virues of RF, if only they
gave it the respect it deserves.)

"Atomic clocks" typically sync themselves periodically (typically during
the evening when signals are strongest, and noise levels subside).  They
free-run on a 32.768 kHz oscillator, just like any other quartz-based
clock.  Their "speed" is not under control of the precise 60 kHz carrier
to which they are tuned.  Only spot checks are made to correct for timing
errors.  In between, you're on your own.

Personally, I don't own an "atomic clock"...  My story's different, but
directly related to my K2/100.

I'm in the process of developing a WWVB-based frequency standard that was
inspired by building and calibrating my K2/100 in 2003.  When I tried to
beat a harmonic of the 4 MHz oscillator against WWV on 20 MHz for
calibration, and couldn't copy WWV on 20 MHz for many days (weeks?),
I knew I had to find a better approach.  Having a test signal of known
precision would have been a nice way to perform the frequency counter
calibration.

I've made quite a lot of progress with the project, and have even used it
along with my K2 in the past two ARRL Frequency Measurement Tests with
very good results.

My antenna is a 40-turn air-core loop, 4-meters in circumference (that's
over 600 feet of wire!).  I cheated and used 40 conductor ribbon cable to
build the loop.  This feeds an Analog Devices instrumentation amplifier (to
maintain electrical balance) that is remotely powered by the receiver (the
antenna and preamp are in the attic).  The rest is a secret (only kidding!),
but it involves balanced synchronous detection, zero IF (baseband) filtering,
and correlation decoding.

Incidentially, I cannot hear WWVB at all using an LF upconverter, a 75-meter
dipole, and my K2.  All I hear is noise.  Yet, I have SOLID copy, any day,
any time, on my specialized receiver, and I'm over 1600 miles from WWVB.

Kinda make you wonder what else is out there, doesn't it?

> If you cannot get it to come into sync within a week, then you probably do
> need an outdoor antenna. I'm sure that many participants in this reflector
> could come up with a practical way to build a 60 kHz external antenna and
> hook it to your clock. If I were doing it, I would look for one of the
> commercially made antennas that are designed for the time servers that some
> computer networks use.

Another approach might be to build a resonant loop (it can be smaller
than the one I described), and place it in proximity, (magnetically coupled)
to your "atomic clock".  This would be similar to the "Select-A-Tenna"
(or similar devices) used to improve AM radio reception in fringe areas.

In closing, don't expect miracles from these clocks.  They are simple
designs that perform best under high SNR conditions.  They appear to be
too easily "fooled" by noise.  They don't do WWVB justice.


73, de John, KD2BD


=====
Visit John on the Web at:

        http://www.qsl.net/kd2bd/


               
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