Hi David:

I've got a number of the WWVB clocks and can see a few of them at the
same time.  It's common that they disagree by a few seconds.

Have Fun,

Brooke Clarke
http://www.PRC68.com

Dr. David Kirkby wrote:

WWVB clocks look at the Time Code treansmitted by WWVB, not at the carrier
which is used for precision timing.

-John

==============

On 25/06/11 20:19, Dr. David Kirkby wrote:

Typically better than 1s. If there is interference or the radio is disabled,
it won't be able to receive the time signal. Switch mode PSUs and CRT TVs
or computer monitors can interfere with the 60kHz time signal.

The clocks with an LCD display usually have an indicator which shows
signal strength if the clock successfully updated in the last hour.
If you have reception problems, try moving the clock. The built-in
ferrite rod is very directional.

Were you receiving Radio 4 on LW or via a digital service. You could
easily see a 3s delay on digital radio or TV.

--
Linux 2.6.32

I have two r-c clocks in the house and they both keep accurate time. One
clock is made by KLIK, the other by STAIGER - both from ARGOS.

The second-hand moves at the very moment I hear the pip, or as exactly as
the eye can tell. But I do not use Radio 4. Instead I check my times using
the pip sequence from RWM's time service broadcasts on either 4.996 or 9.996
MHz (good signal strengths in UK).

There is a danger with broadcasters these days that their studio source goes
through digital buffering and will be subject to delays. The time difference
between identical broadcasts via analogue circuits and digital circuits is
in the order of two seconds.
BBC time pip accuracy can be checked by listening to them at the same time
as listening to RWM.

Ron
G3SVW

----- Original Message -----
From: "Dr. David Kirkby" david.kirkby@onetel.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Saturday, June 25, 2011 8:19 PM
Subject: [time-nuts] How accurate are cheap radio controlled clocks?

On Sat, Jun 25, 2011 at 12:19 PM, Dr. David Kirkby
david.kirkby@onetel.net wrote:

I have a Casio watch that syncs to WWVB when I leave it near a window
overnight.  There's an indicator on the display that shows if it
synced sometime since midnight today (local time), as well as a mode
that will tell you the last time it did successfully sync.  So far,
whenever it has synced today, the difference between it and a
NTP-synced computer time display has always been a fraction of a
second.  Not zero, but well below a half second.  (And when comparing
to a computer, remember that graphics cards and LCD monitors may add
multiple frames of delay).

If the watch doesn't sync for a few days, its timekeeping slowly
drifts but it still takes days to accumulate one second of error.
When I first purchased it, it was 25 seconds fast but the status
display said that the last successful sync was about 8 months ago, so
the internal crystal is likely good to about 3 seconds per month.

On the other hand, I have often heard over-the-air time beeps from
radio stations that are off by 5 seconds or more, usually late.  I
don't know if they are generated by the studio's own clock that is
hand-set and not very accurate, or if the beep is accurately generated
at the mixing board but then fed through something that causes a
significant delay.  (For example, live radio programs have a
multi-second delay between studio and transmitter so they can bleep
out "bad words" that a caller might say before they are broadcast).
So I wouldn't trust a radio time beep for anything without first
comparing it to another source.

 Dave

John wrote:

The ones I have do not monitor WWVB constantly -- they do it once a
day in the middle of the night (signal permitting), at which time
they synch up and update an oscillator correction factor based on how
far they were off since the previous update.  Mine seem to stay
within 500 mS over 24 hours compared to 1PPS "ticks" from a
Thunderbolt (subject to the resolution limits of using my eyes and
ears as the two measurement inputs and the comparator between my
ears), which is as close as the Lady Heather display clock on my system.

Perhaps some newer WWVB clocks monitor more often than that, or even
constantly, but I have not seen any that synch more often than once
every 24 hours.  On one of mine, you can turn the WWVB Rx off.  The
instructions indicate that the expected battery life goes up 12-fold
if you do, which may explain why they don't recalibrate more often.

Best regards,

Charles

Hey Ed,

How are things in the land of mold, mildew and Jamesions?

Best 73,

Had
K7MLR

A fine is a tax for doing wrong.  A tax is a fine for doing well.

Peter Cooper, of Fermi Lab, says, "Every experimentalist knows
that the apparatus, or at least your understanding of it, is
always at fault until demonstrated otherwise." He also says,
"Nature is really unmoved by what I, or anyone else, believes."

On 06/25/11 08:45 PM, Eamon Skelton wrote:

I don't think there's an SMPS nearby, but there was a 100 W amateur transceiver.

Thanks.

198 kHz longwave - using a Kenwood HF transceiver which has general coverage
receive.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

David,

Be aware that if listening via digital radio (or worse, digital TV) there
is a delay in the transmission chain of up to several seconds (DTV).  I
expect you know that already!  Use the FM signal for best results.

Here, I have a couple of analogue display and a couple of digital display
"radio clocks".  The digital are both about a quarter of a second slow,
and the two analogue display clocks are spot-on, as near a damn it.

I'm located in Edinburgh and using the Anthorn 60KHz souce:
http://www.npl.co.uk/science-technology/time-frequency/time/products-and-services/msf-radio-time-signal

BTW: the "pips" went missing recently:
http://www.bbc.co.uk/news/uk-13610203

Hope that helps.

Cheers,
David

SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-taylor@blueyonder.co.uk

On 06/26/11 07:25 AM, David J Taylor wrote:

I was using 198.00 kHz longwave here in the UK. Unless there's some digital
processing going on before the signal is AM modulated, this can't explain the
problem.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?

From: "Dr. David Kirkby" <david.kirkby@.....>
[]

David,

I'm listening to the Radio 3 FM transmission in Central Scotland.  The
07:00 pips appear to be spot on when compared to my GPS-locked PC, using
my simple analog clock program:

http://www.satsignal.eu/software/disk.html#TinyBen

It sounds as if your radio clock is off, so as others have suggested, try
positioning it for a clear, interference-free good strength signal and
retest.

Cheers,
David

SatSignal software - quality software written to your requirements
Web:  http://www.satsignal.eu
Email:  david-taylor@blueyonder.co.uk

I have a cheapie digital "atomic" clock I bought at Walmart several years
ago, and I forget the brand, but it works spot on with my PC's clock. That
is as long as you make sure to place it where the signal is strong enough
for it to update itself. However, it does not update all the time, and
reads the WWVB signal at around 4 in the afternoon and at several times to
sync itself. I think they set it at that time because of signal strength on
the east coast being it strongest about then.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 6/26/2011 at 5:37 PM David J Taylor wrote:

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

signature database 5851 (20110206) __________

David,

I think Radio 4 on 198 kHz is straight through analogue - no digital
buffering with its inherent delays. Yesterday afternoon (1200 UTC I think),
I listened to the BBC pips from Droitwich at the same time as the pips from
RWM on 9,996 kHz, and I watched the second-hand of my Steiger
radio-controlled clock. All three were in exact synchronism - no error
between them, as closely as the ear and the eye could tell.

Are there different ways these radio-controlled clocks are synched to time
signals? I have never seen any perceivable error between my clocks and
analogue broadcast "pips" from MSF, RWM or WWV, so I don't think the synch
scheme is a corrective one. I will try keeping one of my clocks in a Faraday
screen for a while to see how far it drifts in terms of time.

I know of the other two 198 kHz transmitters at Westerglen and Burghead, but
don't know whether they have the same accuracy as Droitwich's frequency
standard. Do they carry the same phase modulation as Droitwich for
teleswitching?

Ron, G3SVW
Manchester

----- Original Message -----
From: "Dr. David Kirkby" david.kirkby@onetel.net
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Sunday, June 26, 2011 3:22 PM
Subject: Re: [time-nuts] How accurate are cheap radio controlled clocks?