atomically correct time

[eli]

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

does anyone have any suggestions

 

[James T. White]

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

does anyone have any suggestions

Why not use a GPS receiver and get it the same way the cell sites get time?

 

[Michael Black]

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

does anyone have any suggestions

The clocks only update once a day. Realistically since they are crystal
controlled even if they can't update for a few days, the average person
will never notice. Clocks go out of time because they aren't set exactly
right (ie they use the wrong "standard" to set them to, or they are sluggish
in pressing the button), and because over a very long time the inaccuracy of
the crystal (or the AC line if they use that for the timebase) is off and
the accumulated error adds up. But you are hardly likely to notice
that a clock is off until it has been long enough since it was
set, or in the case of the "atomic clocks" since it last sync'ed up.

Michael

 

[night dalits]

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

does anyone have any suggestions

they sell the electronic clock that works on wwb at 10mhz atomic clock at
woodcraft stores cheap to build atomic wood clocks,

 

[artie]

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

does anyone have any suggestions

Cheap:

www.klockit.com -- wwvb synchronized clock movements (from about $10).

Not so cheap:

search eBay for Z3801A -- a GPS disciplined 10 MHz time base (clock
hands extra, around $400, and that's what cell sites used to use)

 

[Ben Bradley]

I at first thought the subject was "Anatomically correct time."
Surely that's no reflection of what's on my mind...

I was wanting to design a clock that updated by both
-the atomic clock radio signal
-cell phone towers

this is because the atomic clock signal sometimes is hard to get so I
figured that cellphone towers are more reliable

Alternatively (or along with other suggestions), you could use a
more precise oscillator that will keep you closer to the actual time
when your receiver isn't getting a good enough signal. Check out the
DS32kHz, IIRC it's good to within seconds a year.

does anyone have any suggestions

Even worse than a temporary signal fade, perhaps someday society
will break down and all these signals will be gone, then how will
anyone know what time it is?

Well, here's a solution. Go to http://leapsecond.com/ and scroll
down to and click on the fourth picture, the "Most Accurate
Wristwatch." No doubt there is an Agilent distributor standing by to
take your order.

 

[Glenn Gundlach]

The clocks only update once a day. Realistically since they are crystal
controlled even if they can't update for a few days, the average person
will never notice. Clocks go out of time because they aren't set exactly
right (ie they use the wrong "standard" to set them to, or they are sluggish
in pressing the button), and because over a very long time the inaccuracy of
the crystal (or the AC line if they use that for the timebase) is off and
the accumulated error adds up. But you are hardly likely to notice
that a clock is off until it has been long enough since it was
set, or in the case of the "atomic clocks" since it last sync'ed up.

Michael

What are you talking about the power line being wrong? Short term it
may be off but long term it's right on. SO- build a clock that uses the
power company as a time base and then add a WWVB of GPS receiver to
set/verify your time. Galleon has a WWVB receiver, antenna and RS-232
interface to your computer for about $60. See
http://tf.nist.gov/stations/wwvbtimecode.htm
for the data format from the receiver. If I read it correctly, it's a
continuous update, not just once per day.

For a cheapy frequency reference, the color subcarrier from a network
TV station should be really close to 3579545 Hz. FCC requires them to
be +/- 10 Hz but they're usually much closer than that.

GG

 

[dave]

The clocks only update once a day. Realistically since they are crystal
controlled even if they can't update for a few days, the average person
will never notice. Clocks go out of time because they aren't set exactly
right (ie they use the wrong "standard" to set them to, or they are sluggish
in pressing the button), and because over a very long time the inaccuracy of
the crystal (or the AC line if they use that for the timebase) is off and
the accumulated error adds up. But you are hardly likely to notice
that a clock is off until it has been long enough since it was
set, or in the case of the "atomic clocks" since it last sync'ed up.

Michael

I think the idea is to get the clock signal and send it to a primairy
device and the idea is to have it accurate.

I think it is an aproaching the problem from 2 different angles

 

[Paul Burke]

Why did I read this as 'anatomically correct time'? Like Hubert in Sir
Henry at Rawlinson's End:

"In his adolescence, during the long summers of yesterday, he would
throw himself naked onto the lawns in a northerly direction parallel to
the earthly axis. And with a bluey roman clockface tattoo'd about his
private parts, think about Jean Harlow very hard and - from the shadow
cast -tell the time with remarkable accuracy. "Look! No hands!" In
winter he tried with birthday candles stuck in the end but he was hours
slow and the drips hurt. Later, Henry told him to 'put a sock' on the
sundial bit."

<http://homepages.tesco.net/sansun/Rawlinson End Book.htm>

Paul Burke

 

[Michael Black]

I at first thought the subject was "Anatomically correct time."
Surely that's no reflection of what's on my mind...

No, for some reason the same thought crossed my mind.

Michael

 

[Jim Thompson]

No, for some reason the same thought crossed my mind.

Michael

Me too ;-)

...Jim Thompson

 

[Jim Yanik]

For a cheapy frequency reference, the color subcarrier from a network
TV station should be really close to 3579545 Hz. FCC requires them to
be +/- 10 Hz but they're usually much closer than that.

GG

Note that NTSC standard TV signals are due to go off the air in 2006,IIRC.
Due to the forced move to HDTV.

 

[Jim Thompson]

Note that NTSC standard TV signals are due to go off the air in 2006,IIRC.
Due to the forced move to HDTV.

Nonsense. It's DTV not HDTV and...

"The change to digital TV is triggered no sooner than the end of 2006,
but only when 85% of U.S. homes can receive a digital television
picture. Apparently that doesn't mean 'are capable of receiving the
signal,' but rather 'have the equipment to view a digital television
signal.'

I find it difficult to imagine digital TV market penetration being
anywhere close to 85% less than <two> years from today."

I have SEVEN NTSC sets in the house.

I receive signal via Cox Cable.

Unless Cox Cable can provide me with a signal that the new sets can
tune WITHOUT A SET-TOP BOX, there is no way I will switch.

But I could probably just cease TV altogether. For instance my office
TV is always tuned to Fox News and my back is to it, so radio would
suffice.

In the evening we generally just watch a movie from our collection of
nearly 300 DVD's.

...Jim Thompson

 

[martin griffith]

On Fri, 05 Aug 2005 04:16:20 GMT, in sci.electronics.design Ben

snip

, perhaps someday society
will break down and all these signals will be gone, then how will
anyone know what time it is?

If that happens, a sundial will be all that is required, and a
knowledge of when to plant crops


martin

 

[Spehro Pefhany]

Note that NTSC standard TV signals are due to go off the air in 2006,IIRC.
Due to the forced move to HDTV.

Does anyone still receive terrestrial analog TV signals over the air?

I wonder where the subcarrier frequency is generated for the NTSC
signals we get out of the coax (which are converted from digital, it
looks like). Anyone know? I'm guessing it's in the distribution
boxes.


Best regards,
Spehro Pefhany

 

[Rich Grise]

Does anyone still receive terrestrial analog TV signals over the air?

Yup. I've even built a little Yagi for channel 56.

Thanks,
Rich

 

[Spehro Pefhany]

Yup. I've even built a little Yagi for channel 56.

Thanks,
Rich

What's so interesting about channel 56?

Back in the 70s we had a channel 79 (now channel 57 broadcast
frequency) which showed racy movies every Friday night. People bought
directional UHF antennas just to get them (they didn't really have
much of a broadcast antenna either at the time). Now the signal from
the world's tallest free-standing structure is powerful, but the
movies are long gone.


Best regards,
Spehro Pefhany

 

[Jim Thompson]

On Fri, 05 Aug 2005 13:49:51 -0400, Spehro Pefhany

[snip]

Does anyone still receive terrestrial analog TV signals over the air?

What do you think those towers on Phoenix South Mountain are for ?

I wonder where the subcarrier frequency is generated for the NTSC
signals we get out of the coax (which are converted from digital, it
looks like). Anyone know? I'm guessing it's in the distribution
boxes.


Best regards,
Spehro Pefhany

...Jim Thompson

 

[Michael A. Terrell]

I wonder where the subcarrier frequency is generated for the NTSC
signals we get out of the coax (which are converted from digital, it
looks like). Anyone know? I'm guessing it's in the distribution
boxes.

Most tv stations use a framestore at the transmitter site to remove
switching glitches and regenerate the sync with a 4* colorburst crystal,
like the cheap ones used on computer boards. There is no oven or
temperature control, and most stations don't have an in house frequency
standard to tweak the circuit after it is at normal operating
temperature. Add changes in temperature due to time of day, heat load
on the air conditioning and how the cold air is distributed in the
control room its a crap shoot. I had to try to sync to framestore
systems for a telethon using multiple studios for a telethon once. It
took both engineers over four hours to get them locked and to less than
one degree of phase error.

All of the hard work only worked for a couple days before it had to be
adjusted again. We were forced to use two different models which made
it worse, but I doubt that station will try it again.

I may have the schematic of a framestore in my collection. if I run
into it anytime soon I will scan that page and post it to ABSE.

--
Link to my "Computers for disabled Veterans" project website deleted
after threats were telephoned to my church.

Michael A. Terrell
Central Florida

 

[Rich Grise]

What's so interesting about channel 56?

It's a local indy that shows nostalgic shows like "Magnum PI" and
"Columbo." And there's one that's not so old, "Becker", although
I'm seeing rerun reruns already. ;-)

Back in the 70s we had a channel 79 (now channel 57 broadcast
frequency) which showed racy movies every Friday night. People bought
directional UHF antennas just to get them (they didn't really have
much of a broadcast antenna either at the time). Now the signal from
the world's tallest free-standing structure is powerful, but the
movies are long gone.

Yeah, now to get free porno, you have to use USENET. ;-P

Cheers!
Rich