US Atomic Clock question
 

I have one of these Oregon Scientific ExactSet Radio Controlled gadgets... according to the manual, this thing is supposed to set itself on its own picking up a radio signal from the US Atomic Clock.

So here goes the question.... since Im using this "thingie" in the Southern Hemisphere, namely down under to the left, here in Buenos Aires.... can I expect this apparatus to pick up this signal?

I know I can set the clock manually.... but I kinda wanna have it do its thing on its own.

Thanks,
Gaucho

Depending on the model, it may pick up the signal. I've not seen one that you can adjust for that timezone though if it was a US one, they only go to Eastern and you need one more hour.

Wirelessly posted (Palm TX: Mozilla/4.0 (compatible; MSIE 6.0; Windows 98; PalmSource/Palm-D050; Blazer/4.3) 16;320x320)

Thanks.... it is a US model.

Alex, I don't think it's possible. I have a couple of Oregon Scientific gadgets in BsAs (weather forcaster, wall clock), that have the ability to synchronize with the WWVB-60 signal from the atomic clock in Fort Collins, Colorado.

I never was able to get a signal, and according to the OS web site, you need to be within ~2000 miles of the transmitter. And as mentioned above, the clocks only have offsets for P, M, C and E times (the clocks can't synch in Hawaii, so need for HST). And of course daylight savings time is automatic ...

If you don't have the instruction manuals, you can get the pdf files from the OS web site.

John

Wirelessly posted (Palm TX: Mozilla/4.0 (compatible; MSIE 6.0; Windows 98; PalmSource/Palm-D050; Blazer/4.3) 16;320x320)

Thanks John.

See http://tf.nist.gov/stations/radioclo...m#Anchor-where

I am not sure how those clocks work, but if they sync with the local
radio signals broadcasting NTP (Network Time Protocol) signals, it may work.

Its generally a UTC time so it helps you sync the time accordingly.

I know they have some similar services in several other countries...

do a search.. google is your friend :)

Wirelessly posted (Palm TX: Mozilla/4.0 (compatible; MSIE 6.0; Windows 98; PalmSource/Palm-D050; Blazer/4.3) 16;320x320)

Thanks guys!!

I did some search on it.. and I think you are out of luck with the radio signals.

But I found some interesting information for you:
http://tf.nist.gov/general/pdf/1976.pdf

You might want to set up your computer to use NTP(Network Time Protocol)
to sync with the atomic clock via NTP servers on the internet.

It won't work. You're much too far away from the transmitters.

Someday someone will make one that uses the GPS signals rather than the clock broadcasts but I haven't seen one like that and it would almost certainly have to be a plug-in clock, not battery operated. GPS also has the problem that it doesn't penetrate buildings very well.

Usually the GPS signals are too weak for indoor use.
There are network time server (devices) that can sync time with the
GPS signals, but they need direct line of sight with the satellites.
Most of these units have roof top mounted antennas to make this
work right.

When in doubt just pick up the phone and dial 202.762.1401

I've generally been able to get GPS to work in a window.

I'm pretty sure that the Oregon Scientfic clocks receive the NIST LW transmissions, which on a good day might get a lot further from Fort Collins than the borders of the USA, but are very unliely to reach you in Argentina.

OTOH, if they use the SW service then you might stand an outside chance.

Lots of info on wikipedia - eg http://en.wikipedia.org/wiki/WWVB

The bigger issue with GPS is power consumption. A well designed LW receiver draws a fraction of the paower of a GPS receiver, and should be able to sync in a fraction of the time it would take GPS to get enough of a lock indoors.

A better bet would be to make a clock that could sync to Bluetooth and have your cellphone transmit the time over Bluetooth every now and again (simple software download should be all that would be required).

Yes, that can work if you manage to get three or more satellites in the
line of sight at the same time. If you have 4 or more in sight, you can also
get the accurate location and altitude information.

More of the world DOESN'T have access to time signals than does. Europe, Japan and North America at present are it. Clocks, watches and such won't sync to shortwave,the stations are all longwave. So even where a shortwave time signal exists (China, for example), no longwave devices are possible. Also, unless a device is specifically designed to do so, it won't work outside it's 'home' territory as frequencies and methods of broadcast differ.

OK, so the final conclusion is that I will need to manually set the time for my gizmo.... thanks again to everyone for their feedback.

Related question.... does someone have a clue how (or if) I can change the Temperature reading on the Main Unit from degrees F to Celcius? Ive downloaded the manuals from the website but the manual says nothing about this. The remote sensor units do have a switch in the back panel where you can switch between C and F, but the main unit has no hardware setting for this.

Thanks.

415.767.2676 (415-PopCorn) will also work and it's just as exact :). Actually, it's 415-767-any 4 digits.

While a GPS positioning fix necessarily depends on receiving signals from multiple GPS satellites, to get the right time you only need one.

To get high accuracy (nano seconds) you need to know
how old the GPS signal is. This cannot be done with just one
satellite signal.

All time, all the time!
 

http://tycho.usno.navy.mil/

The official time source for the United States and a number of other countries. I think they also provide GMT. At least the clocks at Greenwich say that they are calibrated by the Naval Observatory time. Due to time delays on the internets it wont be super precise, to the small fraction of a second, but its pretty unlikely that you will miss your flight because of the difference ;)

Errr.... do you not think that, in the case of Greenwich, it might be the Royal Naval Observatory? :D

Not according to my recollection of the sign there on the clock. It said US Naval Observatory, Washington, DC. ;)

Check it out this weekend if you get a chance ;) I wont get a chance to check myself for a bit. Im in the UK at the end of the month but in Cambridge and on a tight schedule. I doubt I will have time to get there.

Wouldnt be the first time I had a faulty memory, but I remember because I was shocked when I saw it since my expectation was the same as yours.

While it's true that the data transmission from all satellites carries the time information (to be exact, the time at THAT satellite), most consumer GPS units won't decode and display that information. Until there are enought SV (satellites) received and decorrelated, the unit will most likely display the time that it's calculated based on time passed from the last fix. Now, when the unit has calculated it's position (minimum of 3 satellites for a 2-d fix, 4 for a 3-d fix), it will also have calculated the Zulu-time for the unit's location (all GPS time is in Zulu/GMT) and will display 'local' based on the device settings.

RFTraveler :cool: :)

Well, I'm shocked, shocked I tell you to read that ;) In truth, it's some years since I've been to Greenwich, so my memory is probably more likely to be faulty.

So I had a quick google: http://wwp.greenwichmeantime.com/info/time.htm seems to confirm your observations.

But it gets much, much worse. Towards the bottom of http://www.greenwich-guide.org.uk/meridian.htm we find out that UTC is actually coordinated from France! :eek:

It turns out that we have our own atomic clock, as I'd thought, as do the Germans, you Americans and loads of other countries: http://www.atomicclockrugbymsf.co.uk/Atomic-clocks.htm (although I'm not sure how up to date this is, as I thought our clock had been moved from Rugby to elsewhere...).

But none of this explains why the US Naval Observatory gets a credit at Greenwich :confused:

Great explanation. ^ thank you.

Most people do not realize that the GPS signals take time to reach
you. The signals travel approximately at the speed of 1,079,252,848.8 km/h
and by the time they reach you, the time ticks are old already.
How old? you can only find out by comparing them to other ticks.

Alex, both my units have a hardware switch C/F - one on the front panel (weather forecaster) and one on the back (clock/temp). The weather forecaster also has barometric pressure mB/inHg switch on the front panel.

Which model do you have?

John

If your radio uses shortwave, you might be in luck. Many countries (at least used to) broadcast time on the same frequencies as the US. 2500, 5000, 10000, 15000 KHz. One wiki page mentions some radio frequencies currently used but definitely in the past there were MUCH more. There probably still are but it isn't listed.

http://en.wikipedia.org/wiki/Radio_clock

BTW, this reminds me of how warped I used to be, listening to those stations for hours at a time. "At the tone, __ hours ___ minutes coordinative universal time. BEEEEEM boom boom boom boom click click duuun click click click ". Especially funny was listening to both Colorado and Hawaii (or other countries) at the same time. Hours of entertainment indeed. The scary thing is that I enjoyed listening to it almost as much as listening to transpacific air traffic.

I don't believe it's "approximately". The metre/meter is defined as the distance light travels in 1/299 792 458 of a second, so the speed of light is exactly 1 079 252 848 800 m/h. Of course light slows down when it hits the atmosphere.

Greenwich is famous for GMT, which is a measure of the Earth's rotation. GMT is so irrelevant for GPS, which uses atomic time (one version of it is the UTC).

For those California numbers (Northern: 767-XXXX, Southern: 853-1212), it's only good if you get AT&T (formerly SBC, formerly Pacific Bell). If you live in Verizon (formerly GTE) territory, its version is no good. Calls from out of the area get connected to AT&T.

Hence the word "approximately" :D

also the reflected signals (often disregarded by the GPS receivers)
can skew the time and distance traveled.

And just a little FYI - this service will terminate after September 19, 2007 due to the withdrwal of the service by AT&T California.

The service is offered under tariff and the tariff is being withdrawn as the equipment supporting the annoucement service is no longer supported by the manufacturer and it is not being replaced by AT&T.