Nice but lacks "day” feature (has “date”). I don’t normally care whether
it’s the 22nd or the 23rd but it’s nice to know whether it’s Tuesday or
Wednesday. YMMV, of course.

Jeremy

On Wed, Mar 14, 2018 at 1:57 PM Achim Vollhardt avollhar@physik.uzh.ch
wrote:

--
Sent from my iPad 4.

On 5 March 2018 at 16:50, William H. Fite omniryx@gmail.com wrote:

What is the most demanding task one would use a wrist watch for? The doors
on trains in the UK lock up to 30 s before the train is due to leave. It is
most frustrating to arrive at a platform, with the train stationary, but no
way to get in. I would estimate that about 20 seconds is good enough for
making a decision about just how fast one has to run for a train.

Buying tickets for events like Wimbledon tennis in the UK can demand one
attempts at the right time, as tickets become available and sold out very
quickly. But one would be using a computer to purchase them, so I don't
think that comes under the requirements of a wrist watch.

Dave

On Wed, Mar 14, 2018, at 6:53 PM, Dr. David Kirkby wrote:

It depends on your job or hobby.

During the Apollo 13 rocket burn before their emergency re-entry, Jack
Swigert used a wrist watch to time the retrorocket burn which was
manually controlled by Jim Lovell. Their normal capsule chronometer was
inoperative. This was mostly a differential (time interval) timing
measurement.
If you needed to determine your location (longitude) and all you had
was a wristwatch and a sextant (and software or a table with certain
information), the accuracy of the distance calculation would depend on
the absolute time accuracy of the watch. At the equator the longitude
error due to time error is (40,075.16 km/day) / (86,400 sec/day) =
463.8 m/sec.
Amateur astronomers need to know time accurate to about a second or
better for accurate osculation observations.
Amateur Radio nets and phone, Skype for Business, or WebEx conference
calls usually start pretty close to the scheduled time. In some cases
people start wondering if the organizer is delayed after about 15 to
30 seconds.--
Bill Byrom N5BB

I concur with Bill.  And even if one keeps tabs on the current watch error,
as is the usual practice by celestial navigators, once that error reaches
or exceeds more than a minute the process frankly gets more clumsy and
error prone.  And if a watch drifts in time very rapidly, one loses faith
in its
ability to coast at a known rate between checks against WWV, which
opportunities are not always available when one wants, due to
propagation issues.

Whatever happened to the quartz watches with trimmer capacitors
for setting the rate?

And radio controlled?  No way!
The process is to delicate and marginal to rely upon.  Give me a
good stable free-running watch any day.

I don't like the solar watch concept mainly because one sometimes
has to go for weeks without an opportunity to expose his watch to
direct sunlight (or some indoor equivalent) for the requisite period
of several hours.

Yesterday I was reading the manual for the Citizen ECO series,
and that thing requires far too much effort and complication to keep
it working and on time.  A good watch must simply work, with no
maintenance beyond occasional battery replacements (and possible
gland replacement at battery-change time), and accurately enough
that the time need never be reset between battery replacements.

I use an old quartz diving watch I bought just under 10 years ago,
(brand no longer distinguishable), which has never drifted more than
about 30 sec (usually less) between battery replacements, and I never
take it off between batteries except when compelled to do so at TSA
checkpoints.  Aside from its LCD's failing I'd be happy to use if forever,
but it's getting awfully hard to read these days.

Dana

On Wed, Mar 14, 2018 at 10:54 PM, Bill Byrom time@radio.sent.com wrote:

Hi

Trimmer caps to set watch crystals are problematic. They are a source of error
as well as a set mechanism. You bump this or that and the trimmer moves. They
also cost money to buy and install properly (no flux in-between the plates …).
Once that is all done you need a way to set them in the factory. Back in the day,
yes, we hat line workers who did that sort of thing. We also sold the crystal in the
watch module (not the whole module) for $2 once upon a time.

How close do you want to set it? In our case, the set was supposed to be < 0.5
ppm of the target. Ideally you needed a design that would do a small fraction
of a ppm in a typical situation.

If the trimmer is a normal device, you get about 120 degrees of travel for the
useful part of the tuning curve. A tune range of 30 ppm for the crystal and another
20 ppm for the other parts would not be unusual. Even taking the 0.5 ppm number,
you are into 120 / 100 = 1.2 degrees sort of set on that little trimmer.

Bottom line: They went away because they weren’t good enough and they were
to expensive …. Setting a modern “shoot the chip” register based module is way
more accurate and reliable. It’s silicon so the cost is whatever sand is selling
for ….

Bob

Most of the quartz watches I've owned were off by about 1-2 minutes per
month,
which I consider inexcusable.

Agreed, the mechanical trimmer is rather problematical, but I'd sure like
to see
*something *that the sophisticated user can tweak at home. Measurement of
the
current rate error is probably not much of a problem; I once tried seeing
the
32kHz signal in the watch by capacitive coupling to the face, and could
detect
the signal.  I just tried a token attempt on my current watch and failed,
but it
was a crude, unshielded attempt by merely laying a 'scope probe against the
watch face.  I was being severely jammed by the local 1230 kHz AM station.
Anyway, the idea is to observe the signal's phase drift while triggering
the 'scope
from a trusted 1PPS source.

So now all that's needed is an alternate way for trimming the watch's
frequency
without opening the case.  There must be a way...

Dana

On Thu, Mar 15, 2018 at 8:13 AM, Bob kb8tq kb8tq@n1k.org wrote:

Dana, the magnetic impulse of a quartz watch stepping the second hand forward is easily picked up by an unshielded coil. Wind a couple hundred turns of magnet wire around a bottle cap and hold near the watch face. Plug into the microphone input of a PC and run audacity to record the waveform. You will see 60Hz/120Hz buzz in the background but the second hand stepping impulses will clearly show as a sharp impulse every second. Of course a small electret microphone can pick up the sonic impulse too and will also be useful for purely mechanical watches.

Broadly I’ve found cheapie quartz watches to be way more accurate than a minute a month. In the past I’ve marveled here about my cars clock which drifts less than a minute every 6 months (DST change reset interval) despite being in a very adverse temperature range.

Tim N3QE

Hi

The most common way to pull the 32KHz signal off of a watch is via a tuned
microphone. At least that’s the way we did it in production. A watch crystal
can (but usually doesn’t) move > 100 PPM with temperature. When things
are set up, assumptions are made about “your” temperature environment. If
the watch is off temperature vs the assumptions, it will not keep good time.

Some numbers:

10 seconds a month is 3.8 ppm
120 seconds a month is 46 ppm

The temperature curve is parabolic so usually temperature will result in a
slow watch. If the “target” set point is 10 seconds fast, you would need to
be right at 50 ppm off to loose two minutes a month.

If you take a look a the previous numbers on trim range on the trimmer. A
trimmer that will do +/- 25 ppm is “adequate” for setting the watch in production.
It’s not good enough (by a factor of 2) to take care of a 2 minute / month timing
error.

Just for the record, I don’t think I have ever owned a quartz watch that was
off by more than a 15 seconds per month. I’ve owned cheap ones and expensive
ones. They all have done pretty well. The fancy ones have done better ….

Bob