"Atomic Clocks"

[Norm Dresner]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

TIA
Norm

 

[Barbarian]

No.


The "atomic clocks" just recieve the time from NIST a few times a day... to
the nearest second. Not the kind of signal to calibrate any instrument to.


Dennis
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[Richard Henry]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

In the USA, you can receive various signals from NIST transmitters (10 MHz
"exactly" is one, I think). However, you must be aware of ionospheric
effects that can cause an apparent frequency shift near sunrise and sunset.

 

[K8JLF]

In the USA, you can receive various signals from NIST transmitters (10 MHz

"exactly" is one, I think). However, you must be aware of ionospheric
effects that can cause an apparent frequency shift near sunrise and sunset.

The stations in question are WWV (10Mhz) and WWVH (15Mhz) as far as I know. WWV
broadcasts from Fort Collins, Colorado, and WWVH is based in Honolulu, Hawaii
if I recall correctly. They at least used to be on other frequencies as well.
Mostly good for setting a watch by. They broadcast a tone every second, and a
different one on the minute. I have a piece of equipment somewhere in my garage
that uses their signal to generate a timing output to control something else
(designed for traffic control I think)

 

[Robert Baer]

The stations in question are WWV (10Mhz) and WWVH (15Mhz) as far as I know. WWV
broadcasts from Fort Collins, Colorado, and WWVH is based in Honolulu, Hawaii
if I recall correctly. They at least used to be on other frequencies as well.
Mostly good for setting a watch by. They broadcast a tone every second, and a
different one on the minute. I have a piece of equipment somewhere in my garage
that uses their signal to generate a timing output to control something else
(designed for traffic control I think)

WWV frequencies are 5, 10, 15 and 20MHz; transmit grequencies are
based on the standard they keep, but transmission path effects can cause
received variations which tend to average out.
There is encoded info at the end of every minute and i think more info
at each hour; perhaps the NIST website has info concerning that coding.

 

[Tim Hubberstey]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

A lloonngg time ago, I read that the most accurate frequency reference
that is readily available is the 3579545 Hz color subcarrier oscillator
in a TV when it is receiving (phase-locked to) a color video signal. The
reasoning was that the subcarrier generated back at the network was
NIST-traceable so the local oscillator would be too. I don't know if
this still applies given current distribution methods for cable signals
but it might still apply for over-the-air transmissions.

I've never actually tried it myself... poking around inside a live TV
has never been my cup of tea.

 

[David L. Jones]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

TIA
Norm

A few ideas:

1) If 1Hz is OK (your frequency counter would have to be able to do
gating measurement), then a GPS receiver with a 1Hz reference output
will beat almost any other reference available.

2) You can get used Rubidium standards on eBay, that will get you
10^-11
Many Rubidium standard can also be locked to a 1Hz GPS reference.

3) There have been a few projects over the years which extract the
15.625KHz (I think for PAL) frequency from a TV set. The theory being
that the reference used by the Tv station is of rubidum quality or
better.
This was a standard way to calibrate frequency counter kits in the
past, at least here in Australia, I don't know about the US and NTSC.

5) Hire a Rubidium standard for a day.

4) Don't bother tweaking your frequency counters, the drift of their
(presumably) non oven controlled crystal with temp is going to be all
over the place anyway :->

Dave

 

[David L. Jones]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

TIA
Norm

A few ideas:

1) If 1Hz is OK (your frequency counter would have to be able to do
gating measurement), then a GPS receiver with a 1Hz reference output
will beat almost any other reference available.

2) You can get used Rubidium standards on eBay, that will get you
10^-11
Many Rubidium standard can also be locked to a 1Hz GPS reference.

3) There have been a few projects over the years which extract the
15.625KHz (I think for PAL) frequency from a TV set. The theory being
that the reference used by the Tv station is of rubidum quality or
better.
This was a standard way to calibrate frequency counter kits in the
past, at least here in Australia, I don't know about the US and NTSC.

5) Hire a Rubidium standard for a day.

4) Don't bother tweaking your frequency counters, the drift of their
(presumably) non oven controlled crystal with temp is going to be all
over the place anyway :->

Dave

 

[Roger Lascelles]

If your frequency counter has a 1 MHz or 10 MHz oscillator output, or you
can use it to measure a separate 1 MHz or 10MHz crystal oscillator, then you
can use a shortwave radio and mix a little of the oscillator (or a harmonic
of the oscillator) in with the shortwave WWV signal. I use 10MHz WWV.

The mixing is an art form - while receiving a healthy WWV signal, wind a
piece of wire connected to the oscillator around the telescopic antenna on
your shortwave receiver. You have to get similar amounts of both signals.
When you have similar proportions, you will hear a tone ranging from a beep
down to a growl. Tune the oscillator so the growl becomes a slow pulsing
whoosh. The frequency of the whoosh is the difference between the WWV and
oscillator frequencies. For a simple oscillator or counter, you can get the
difference down to 1 cycle quite easily - that is 1 in 10 million. A simple
oscillator / counter can't hold that accuracy for long, but it can hold 1 in
a million for minutes, and 1 in 100000 over months.

This is a practical way to get your frequ meter adjusted. The phase shift
due to shortwave propagation is not an issue at around the 1 cycle beat
note - in fact can do 1 cycle in 10 seconds on WWV here in Australia !

Roger

 

[Guy Macon]

2) You can get used Rubidium standards on eBay,

Here is one in the $250 to $350 range:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3856526769

 

[Leon Heller]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could
be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a
reasonable
standard.

Try this: http://www.geocities.com/icdx_australia/poor_mans_caesiumclock.htm

I keep meaning to build an updated version with a CPLD replacing the 74HC
logic.

Leon

 

[Mac]

WWV frequencies are 5, 10, 15 and 20MHz; transmit grequencies are
based on the standard they keep, but transmission path effects can cause
received variations which tend to average out.
There is encoded info at the end of every minute and i think more info
at each hour; perhaps the NIST website has info concerning that coding.

I think WWV was originally set up for mariners, who need accurate time to
do celestial navigation.

For those of you interested in celestial navigation or observing the
heavens, the WWV signal also contains (or used to contain) information
about sub-second discrepancies between clock time and celestial time.
Celestial time is what you would use to look-up or calculate coordinates
of celestial bodies.

When the discrepancy becomes large enough, leap seconds are inserted or
removed. Thus, UTC (fka GMT) is never more than a second off of almanac
time. The sub-second discrepancies are reported by using a slightly
different tone for the seconds following the exact minute.

Also, there are (or used to be) synthesized-voice, ocean-weather reports
for various parts of the ocean at various times on WWV. Winter weather
reports for the high-latitude North Pacific are particularly sobering.

--Mac

 

[Roger Hamlett]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

Generally, no.
However it may be that the carrier frequency used on one or more of the
transmitters is deliberately of a high accuracy. This is the case in the
UK, where the Rugby LW transmitter (60KHz), is warranted to have an
accuracy to 2parts in 10^12. The WWVB broadcast from Fort Collins in the
USA, is I think certified to a similar standard.

Best Wishes

 

[Nico Coesel]

There are many inexpensive, so-called "atomic clocks" in the mass market
which AIUI use something like the NIST radio sites to do the time setting.
Is it possible to hack into one of these and extract a signal that could be
used for calibration of instruments. I'm not looking for "NIST Traceable"
but just something to calibrate a bunch of frequency meters to a reasonable
standard.

Use the carrier of a radio or TV station. These are usually very
stable.

 

[Mark Zenier]

The stations in question are WWV (10Mhz) and WWVH (15Mhz) as far as I know. WWV
broadcasts from Fort Collins, Colorado, and WWVH is based in Honolulu, Hawaii
if I recall correctly. They at least used to be on other frequencies as well.
Mostly good for setting a watch by. They broadcast a tone every second, and a
different one on the minute. I have a piece of equipment somewhere in my garage
that uses their signal to generate a timing output to control something else
(designed for traffic control I think)

No, the atomic clocks use the WWVB VLF transmitter running at 60 kHz.

Try Atmel for the receiver ICs, originally from Telefunken.

The modulation is in the NIST publications 432(?). It's on
their web site. Or in _Reference Data for Radio Engineers_.

Mark Zenier [email protected] Washington State resident

 

[Norm Dresner]

Try this: http://www.geocities.com/icdx_australia/poor_mans_caesiumclock.htm

I keep meaning to build an updated version with a CPLD replacing the 74HC
logic.

That looks quite doable but I have a question. Where would you get the
composite video input? Is a composite output of a normal TV set tuned to,
say, a broadcast channel sufficient?

Norm

 

[Leon Heller]

That looks quite doable but I have a question. Where would you get the
composite video input? Is a composite output of a normal TV set tuned to,
say, a broadcast channel sufficient?

Yes. Most UK TVs output composite video on the SCART connector, usually for
connection to a VCR.

Leon

 

[Terry Given]

The stations in question are WWV (10Mhz) and WWVH (15Mhz) as far as I know. WWV
broadcasts from Fort Collins, Colorado, and WWVH is based in Honolulu, Hawaii
if I recall correctly. They at least used to be on other frequencies as well.
Mostly good for setting a watch by. They broadcast a tone every second, and a
different one on the minute. I have a piece of equipment somewhere in my garage
that uses their signal to generate a timing output to control something else
(designed for traffic control I think)

No, the atomic clocks use the WWVB VLF transmitter running at 60 kHz.

Try Atmel for the receiver ICs, originally from Telefunken.

The modulation is in the NIST publications 432(?). It's on
their web site. Or in _Reference Data for Radio Engineers_.[/QUOTE]

which one? I have three, and there are probably a dozen more....

Mark Zenier [email protected] Washington State resident

Cheers
Terry

 

[Mark Zenier]

which one? I have three, and there are probably a dozen more....

The one with the title _Reference Data for Radio Engineers_,
from ITT/Howard W. Sams.

In the Eighth Edition, (_Reference Data for Engineers :Radio, Electronics,
Computers,..._), it's in Chapter 1, in the subchapter titled "Standard
Frequencies and Time Signals".

Mark Zenier [email protected] Washington State resident

 

[Terry Given]

The one with the title _Reference Data for Radio Engineers_,
from ITT/Howard W. Sams.

In the Eighth Edition, (_Reference Data for Engineers :Radio, Electronics,
Computers,..._), it's in Chapter 1, in the subchapter titled "Standard
Frequencies and Time Signals".

Mark Zenier [email protected] Washington State resident

As opposed to the one with the title "reference data for radio
engineers" by Federal Telephone And Radio Corporation

Cheers
Terry