No, the suggestion makes perfect sense. A 12 GHz input board likely
has an internal prescaler with a division ratio that is 4 times that
of a 3 GHz input board, in order to have the main counter running at
the same internal frequency. For example, a 3 GHz input might divide
by 32 while a 12 GHz
Here is a discussion forum page that shows a commercial quartz watch
timing machine in use:
http://omegaforums.net/threads/quartz-watches-some-information-some-may-find-interesting.5475/
The machine obviously measures the time of each second tick, either
electrically or acoustically, because
A few days ago, I took my collection of obsolete handheld GPS
receivers outside and turned them on, to let them find themselves and
collect new almanac data. Most of them probably hadn't been turned on
for 2 years or more. All of them eventually acquired satellites and
started navigating. The
Interesting. It was May 22 this year when I first noticed that my
Garmin 45XL was reporting a date in 1994, exactly 1024 weeks early.
That's also consistent with Garmin having used 768 weeks as their
fence for a GPS week being in the past instead of the future.
It's really the same as the
The clock face has also been redrawn so the rate of time passage is
still positive:
http://www.bbc.com/news/world-latin-america-28013157
I've seen one article that argues that this is more natural in the
southern hemisphere, since the shadow on a sundial rotates CCW there.
- Dave
Is there any reason (other than cost) not to both series-terminate the
source and parallel-terminate the sink?
When I was dealing with analog video, the standard distribution method was :
1. Buffer amplifier with high input impedance, very low output
impedance, and a gain of 2 (so 1 V P-P
I will agree that the end termination is optional if you are delivering a
pulse signal to just one input, which is at the far end of the coax.
However, I think there's still a problem with series-only termination when
the pulse signal is daisy-chained through multiple inputs. When you apply
5
Hello. Please add me to the list of people interested in the LTE-Lite eval
kits.
(I did not send a previous email, and you did not lose it - I've just been
slow in writing).
Thanks,
Dave
On Tue, Sep 23, 2014 at 8:05 PM, S. Jackson via time-nuts
time-nuts@febo.com wrote:
Hello Time-Nuts,
Did you use one-ply, two-ply, or three-ply TP?
More seriously, your LTE-Lite differs in a couple of respects from the
batch of production ones, or at least my example. Your TCXO seems to be
in a metal package (shiny gold colour) and open to the air, if I'm
interpreting the photo on your LTE-Lite
The 20 MHz output should be OK, since it is series-terminated with 50 ohms
at the source and the buffer can source enough current. The driver sees a
100 ohm load (50 ohm resistor in series with 50 ohm coax impedance) for
that 32 ns round trip time, so it will increase power dissipation (as you
I assume the Venus chipset NMEA output sentence set is a subset of the
uBlox NMEA output set, and the NMEA messages are sufficiently
standardized that the uCenter software can read them and display the
results in a meaningful way. Any other program that reads and displays
NMEA data (and can
Programs that try to turn text into a link will get the URL wrong due
to a missing space. Fixed link:
http://gpstime.com/files/tow-time2011.pdf
On Wed, Mar 14, 2012 at 09:05, Azelio Boriani azelio.bori...@screen.it wrote:
And don't forget the usual PDF
It is worth noting that skipping the end termination is probably a bad idea
when daisy-chaining a signal from one output to more than one device input.
The input at the end of the cable will see a clean rise from zero to 5 V
(or whatever the driver's open-circuit voltage is), but the other inputs
For what it's worth, that seems to be the standard way to distribute analog
video (composite or component). A low-impedance voltage source with a gain
of 2 drives a bunch of outputs with an individual 75 ohm series resistor
for each output. Each cable that is connected to an output has a
But if the LED transition was offset any significant amount of time from
the PPS, you wouldn't be able to use it to set your watch!
Dave :-)
On Wed, May 16, 2012 at 10:57 AM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:
Then, to reduce the impact on the PPS signals, the LED on/off
I don't think that's correct. A right-hand spiral (however you define
right-hand) remains right-handed if you rotate the whole object in space so
the centre axis of the spiral points in the opposite direction. A
right-handed spiral is converted to a left-handed one only by reflecting it
in a
Well, they could be consistent.
Most of those photos show only two sizes of helix-type antennas. The
larger diameter (probably lower frequency) are quadrifilar helix designs,
and they are uniformly left hand thread helixes. (I assume that everyone
agrees on what a left-hand thread looks like,
I was invited to dinner with friends, so I took some stuff with me. Before
dinner, I explained the concept of leap second to the hosts' 8-year old
daughter. She understood leap years already, and I think she understood
the leap second explanation too.
As the appointed time (8 PM here, in EDT
I like to think of it this way:
If you are talking instantaneous measurements, then watts is indeed always
volts * amps. With a resistive load, the signs of volts and amps are
always the same, and the product of the two is always non-negative. If you
calculate the average of instantaneous watts
If you care about accurate colour rendering, stick with incandescent,
preferably halogen. White LEDs are actually blue LEDs coated with a
phosphor that absorbs some of the blue light and emits approximately
yellow instead. If you look at the spectrum, you'll see a broad yellow
peak and a
Hmm. Has anyone built a strobe light using LEDs instead of a xenon
flash tube? I can see the appeal of building something that doesn't
need high voltage to fire or trigger the tube. Yes, you probably
couldn't get as much light as a big Xenon tube, but there are
applications where you don't
There are also large differences in rated lifetime; look at the fine
print on the package.
I've had some early Philips units that I used in a timer-driven lamp;
they were on for hours every day. The lamp lasted for years and years
and I eventually threw it out because it had gotten dim (the
In theory at least, a single satellite is enough to provide timing in
position hold mode.
However, that assumes you get a direct line-of-sight signal, with no
multipath. A reflected signal has additional delay that the GPS
receiver cannot factor out if it's receiving only one satellite. If
it
By the way, this doesn't mean that the GA-27 is a poor antenna design,
it's just not the best antenna choice for this situation.
The GA-27 is intended as an external antenna for Garmin's handheld
receivers, which normally operate with passive patch or helix
antennas. So the receiver itself needs
On Tue, Dec 13, 2011 at 08:19, Chuck Harris cfhar...@erols.com wrote:
Metric vs English is purely about a set of arbitrary constants.
Decimal pounds, decimal inches and decimal seconds is just as
arbitrary, and just as easy to use as the metric system.
I would agree, as long as you stay
On Thu, Feb 2, 2012 at 12:21, Tom Van Baak t...@leapsecond.com wrote:
It's possible to use Bresenham with two integers 10,000,000 and
32,768 but I found no way to perform all the 24-bit calculations
on an 8-bit PIC quick enough. Removing the GCD often helps
but in this case the accumulator
I spent a bit of time poking around the SkyTraq web site on the weekend. I
couldn't find a datasheet for the chip on the LTE-Lite - perhaps it's so
new that SkyTraq has not put together the datasheet yet.
Under timing, they only list the Venus638LPx-T, which is a older (2011
copyright on the
What is the source of the 1 PPS you are comparing against?
I compared my LTE-Lite to an old Thunderbolt (original model, single 24 V
input with internal DC to DC converters, Piezo oscillator). At the time,
the Thunderbolt had been running for a few months, while the LTE-Lite had
been running for
One zero-effort way to do this: a portable GFCI.
I have several GFCIs (Ground Fault Circuit Interrupters) designed for
portable use. They may be in the form of an extension cord with the GFI
electronics in the male plug, or a short cord with the electronics in the
middle of the length, or a
In my case, the LTE-Lite had been operating for at least a week before I
made my accumulate mode measurement, and the Thunderbolt had been
operating for at least a month. But both antennas were in poor locations -
not bad enough to lose lock any time I was watching, but nowhere close to a
clear
(this perhaps is what the counter does
internally - I don't know).
I'd like to get to the bottom of this if only to understand my counter
better.
James
-Original Message-
From: Dave Martindale dave.martind...@gmail.com
To: jpbridge jpbri...@aol.com; time-nuts time-nuts@febo.com
: Dave Martindale dave.martind...@gmail.com
To: jpbridge jpbri...@aol.com; Discussion of precise time and frequency
measurement time-nuts@febo.com
Sent: Tue, 17 Mar 2015 0:27
Subject: Re: [time-nuts] ADEV noise floor vs counter gate time
How is the counter configured? Are you reading period
How is the counter configured? Are you reading period or frequency? Are
you in E? (Every Result) mode, or C? (Continuous Result) mode? The
former should give you continuous but independent measurements, while the
latter gives heavily overlapped measurements. (For example, with a 100
second
I wish it was coming to Canada. But according to
http://www.sourcewire.com/news/85588/ships-clocks-stars-exhibition-in-greenwich-ends-sunday-january-4#.VRN-O_nF-uM,
it is heading to two sites in the USA (Folger Shakespeare Library in
Washington DC and Mystic Seaport Museum in Connecticut) plus
Hmm. I'd say that the time setting accuracy may have improved, but the
timekeeping accuracy still isn't wonderful.
I just checked my iPhone, using the Emerald Time app to display the
difference between iOS time and NTP time. The local time was 850 ms fast.
Then I went to Settings-General-Date
The TF930/960 does have a calibration procedure that is performed from
the front panel. Basically, you feed it a stable input from any known
source (so both 1 Hz and 10 MHz from a GPSDO should work) and then
adjust until the displayed frequency agrees with the known input
frequency. The
at 4:23 PM, Dave Martindale dave.martind...@gmail.com
wrote:
The TF930/960 does have a calibration procedure that is performed from the
front panel. Basically, you feed it a stable input from any known source
(so both 1 Hz and 10 MHz from a GPSDO should work) and then adjust until
Standalone receivers don't have to be expensive. Take a look at the GPS
receiver modules at sparkfun.com. They are under $100 (some way under),
and some either require or can take an external antenna, and they
provide 1 PPS output. Garmin themselves sells receiver boards without
integrated
The problem with using a 1 Hz reference when looking at a nominal 10 MHz
signal is that you will get a stable scope display with no drift when the
input is *any* integer number of cycles/sec. So 10,000,000 Hz will give a
stable display, but so will 9,999,999 Hz and 10,000,001 Hz. Unless you
know
Yeah, I considered saying that. But if you don't have a TI counter, you
need some way of resetting the divide-by-1e7 chain so the two 1 Hz pulses
are close enough in time that you can see them on the scope at some
reasonably fast sweep rate. Yes, you can used delayed sweep, but how
stable is the
Which altitude do you have the Thunderbolt set up to report?
If you have the datum set to WGS-84, the Thunderbolt can report either HAE
(height above ellipsoid) or MSL (height above the geoid model) in its
serial output. The choice is controlled by bit 2 of byte 0 of the 0x35
command packet.
It seems odd that the Garmin receiver got it wrong. The Garmin GPS-20 and
-25, which I think are both older than the 18x, get it correct. The GPS-20
is so old it is a single-channel receiver, the GPS-25 is 12-channel but
still 5 V power.
GPS-20, June 1998:
Tomorrow evening, I'm going to a leap second barbecue. The barbecue itself
was the idea of a friend, but I'm bringing the equipment to show the leap
second.
My main setup is a Thunderbolt, Lady Heather running on a PC laptop, and a
serial to USB converter. It's all working sitting here on a
It's not just synchronous-motor clocks that use line frequency as a time
reference. I have a Heathkit alarm clock that counts cycles of line
frequency as its timebase. I think that was common in the early
generations of NMOS clock chips. The clock does have a backup oscillator
(powered by a 9 V
How did you find the units that will act as a UPS, without buying
everything on the market and testing them?
I just checked all of those bricks in our house, and none will do it.
There are a couple of PNY units that do not provide output power until a
button is pressed, and don't charge until
(Long-term members of the list can skip this; you've seen it many times
before. But it sounds like Clint is new, and could use some basic
explanation. I was in his position once too).
It sounds like you are assuming that the GPS receiver's internal oscillator is
locked to GPS time. In most
Two data points for one watch:
When I bought a Casio PAW-1300, it was about 20 seconds fast. It said that
it had last synced on September 24, but that information does not include
the year. It was now June 10, so it had been running without a radio sync
for at least 9 months (though it could
Someone is in the process of writing open-source watch timing software.
You may want to look into it.
It was announced here:
http://forums.watchuseek.com/f6/open-source-timing-software-2542874-post21977314.html#poststop
It contains these links:
First the goodies. Here are Windows binaries
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision
Wouldn't that be "un pied dans chaque hemisphere" in France?
I visited the Greenwich observatory a number of years ago, but it was after
5 PM and all of the exhibits were closed for the day. So we only saw the
repeater clock and the meridian line. One interesting fact: A GPS
receiver will not
Hmm. When I was there yesterday I didn't see any "No Photography" signs,
so I photographed lots of the exhibits, including the four Harrisons . I
used flash, so I wasn't the least bit stealthy, and one of the staff was
only a few feet away. Maybe they no longer care?
Dave
On Wednesday, 6 July
If the "big digital clock" doesn't display the time with fractional-second
precision, then it only needs to be updated at 1 Hz, which can be done with
the 1 PPS directly. Consider replacing the 32 kHz crystal, divider chain,
and microprocessor with a new microcontroller that takes 1 Hz input and
Recently, I was invited to an event to celebrate the addition of a leap
second.
I thought I would provide the entertainment by bringing a suitable GPS
receiver
plus a laptop running Lady Heather. I had done this before, so I thought it
would be easy, but a whole collection of things went wrong,
The LTE-Lite User Manual (version 1.3) says:
2.3.7 1 PPS Module outputs
The LTE-Lite SMT Module provides GPS raw 1 PPS CMOS pulse on pin 15 with
sawtooth present, and a clean TCXO-generated, sawtooth-removed, UTC(GPS)
phase-locked 1PPS output on pin 4.
It is the pin 4 output that connects to the
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