In message 20141019233526.znmkx...@smtp11.mail.yandex.net, Charles Steinmetz
writes:
A proper digital filter that computes a new
running value at least every second will be more
complex than that, but you're right, it's not an unfathomable task.
No, it will not, a simple running
Bob,
Since the satellite orbit the earth with a period of 11 hours and 58
minutes, it is actually twice a day.
Cheers,
Magnus
On 10/20/2014 03:50 AM, Bob Camp wrote:
Hi
The GPS constellation repeats roughly once a day. It is not at all uncommon to
have a “worst case” sattelite geometry
The constellation may repeat at 12hr intervals , but at any static position you
will only see one per day , no? , the other being 180 degrees way. I only get
one regular bump.
Le 20 oct. 2014 à 09:43, Magnus Danielson a écrit :
Bob,
Since the satellite orbit the earth with a period of 11
Bob,
Since the satellite orbit the earth with a period of 11 hours and 58
minutes, it is actually twice a day.
Cheers,
Magnus
I've been reminded of that before, but the fact remains that here the
interruptions when they happen are at 24-hour intervals, not
Having build GPSDO's since Brooks came out with his in QST I learned a few
things and always worked on improving its performance And hopefully the FE
405B project that lasted over nine month will top any thing in GPSDO's. The
FE5680A is nearing final Beta test and hopefully will soon be out
Poul-Henning wrote:
PLLs are really not that hard [context: we have been discussing
all-digital PLLs (ADPLLs)]
Yes, I know -- I have designed more than a few. I have also reviewed
more than a dozen hobbyist designs and modeled some of them, and
found that few hobbyists seem to have
Hi
Yes, but there’s this large object in the sky that modifies the ionosphere as
it travels in a “about one a day” track. It appears to be coming up just about
now, but I do need more coffee to be sure …
The combination of the constellation and the ionosphere are what I believe give
you the
Bob,
You mean the Sun, correct?
Regards,
John
On Oct 20, 2014 4:16 AM, Bob Camp kb...@n1k.org wrote:
Hi
Yes, but there’s this large object in the sky that modifies the ionosphere
as it travels in a “about one a day” track. It appears to be coming up just
about now, but I do need more
Hi
Gee, now after a few cups of coffee … yes that does appear to be the sun.
The GPS system does it’s best to model the ionosphere and transmit that data.
Unfortunately the model / model resolution is not as good as it could be. That
lets the ionosphere creep into the solution more than
Hi
We tend to focus on this or that enhanced feature in a piece of code. It’s fun
to talk about. That’s not what keeps most designs from doing what they should.
By focusing on this rather than the testing required, we set people up to fail.
If you start off the project believing you mostly
having kept watch over oscillators for about half a century now... My first
assumption would be that a once-a-day bump in time offset or tuning word,
is due to earthside changes especially temperature of the earthside
oscillator environment.
Tim N3QE
On Sunday, October 19, 2014, Bob Stewart
From: Dave Cawley
Dartmouth United Kingdom
Femtosecond Systems FSS 600 phase noise detector
Guys
Just won this on eBay. Try as I might, I can't find any details especially a
circuit/schematic diagram. Can anyone help please ?
Thanks
Dave
___
On Mon, Oct 20, 2014 at 2:43 AM, Magnus Danielson
mag...@rubidium.dyndns.org wrote:
Bob,
Since the satellite orbit the earth with a period of 11 hours and 58
minutes, it is actually twice a day.
But then your house has only completed half an orbit.
--
Brian Lloyd
Lloyd Aviation
706
The GPS satellites are at an altitude that gives them an orbit of 12* hours.
But during that time the earth has made half a rotation. Thus it takes -two- SV
orbits and -one- earth rotation to get back to the same geometry. It is this
24* hour ground-track repeat time that is of interest in
Bob wrote:
We tend to focus on this or that enhanced feature in a piece of
code. It's fun to talk about. That's not what keeps most designs
from doing what they should. By focusing on this rather than the
testing required, we set people up to fail. If you start off the
project believing you
Stu,
Many thanks for the heads-up on htese units. Great deals.
Can you advise the size of these units? Are they full-size 19 rack mount
or the half-size units like the Z3801A?
Can the REF-1 unit (the one with the GPS receiver) be operated separately
from the REF-0 unit?
There is a mod on
http://phk.freebsd.dk/time/20141018.html
PHK,
This is the best news I've heard in a long time; an overhaul of NTP!
One suggestion I'd like to make. You've seen the GPSDO simulator code I started:
http://leapsecond.com/tools/gpsim1.c
And you've seen the growing collection of GPS receiver and
Dave,
The seller is offering the REF-0 and REF-1 units at $75 each plus
shipping. When I searched for Lucent KS-24361, I found the
original item with both, as well as the individual units.
--Glen Hoag
h...@hiwaay.net
At 10:22 AM 10/20/2014, you wrote:
Stu,
Many thanks for the heads-up on
In the link below there's a photo of one of the units with a ruler against it -
11 wide.
Anthony
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dave M
Sent: Monday, October 20, 2014 10:22 AM
To: Discussion of precise time and frequency measurement
Hi Glen,
I'm looking at this unit, but I have to say that I can't make any sense from
the listing. I don't know what the REF-0 and REF-1 units do, and I don't know
whether they need to be connected to a Z3810AS, which I don't have. Could you
or someone elaborate on exactly what these are?
On Mon, Oct 20, 2014 at 6:48 AM, Bob Camp kb...@n1k.org wrote:
Hi
We tend to focus on this or that enhanced feature in a piece of code. It’s
fun to talk about. That’s not what keeps most designs from doing what they
should. By focusing on this rather than the testing required, we set people
Oh, duh. Sorry. I missed the relevant post. Never mind. Now I'll go feel
embarrassed for awhile.
Bob
From: Bob Stewart b...@evoria.net
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Monday, October 20, 2014 11:59 AM
kb...@n1k.org said:
The combination of the constellation and the ionosphere are what I believe
give you the once a day (rather than once per 12 hours) bump.
There is another layer. In addition to the normal once-a-day type
differences, the pattern of satellites drifts slowly from day to
Well, may memory was somewhat faulty. The units I have are
3ZN2PD-1910-1. There is a seller on ebay with the same thing:
http://www.ebay.com/itm/Mini-Circuits-3ZN2PD-1910-1-RF-Power-Splitter-LUCENT-COMCODE-408781904-/131191412618
If anybody is interested, I'll let mine go for $20 shipped in
Stu said:
Power is applied to the connector labeled +24VDC and P1, in exactly the
same way as the earlier RFTG units. Apply +24V to pin 1 and the other side of
the power supply (GND or RTN) to pin 2. In these units, that power supply goes
directly to an isolated Lucent DC/DC converter brick
Arg! I read the whole article on the mod but just didn't see the ruler.
Oops!
Thanks for the alert,
Dave M
Anthony Roby wrote:
In the link below there's a photo of one of the units with a ruler
against it - 11 wide.
Anthony
-Original Message-
From: time-nuts
In message 60CC0E034928B664249EAC88407F@pc52, Tom Van Baak writes:
http://phk.freebsd.dk/time/20141018.html
PHK,
This is the best news I've heard in a long time; an overhaul of NTP!
Indeed :-)
Instead of tweaking GPSDO algorithms or tuning parameters and
having to wait days to
In message CAGVVbuGv_-cFDAA=T6hGE1ey32=omxxcg-cxub5scusao_t...@mail.gmail.com
, Brian Lloyd writes:
So why not do the GPSD hardware, software, [...]
It would be a really worthwhile project in general, and it could be
made very general with very little trouble.
I would find a cheap ARM
Hi Brian, Bob, Charles, et. al.
Bob has a great point about the difference between a one-off in a basement
lab, and a commercial product that has to work under any circumstances,
wether flying at 50,000 feet at -56C, or in an urban canyon, or under whatever
other stress could be thrown at
This weekend I walked over the the park next to where I live. In that park
is a water tower/tank with its safety railing covered in cell transceivers.
Looks like there are 3 providers, based on the number of power company
watthour meters I can see.
Each has their own GPS antennas, two of which
Said
Having some fun reading your posts on time-nuts.
I placed an order last Friday or Saturday for one 20 Mhz unit. But a couple
of funny things seemed to happen like ebay saying 2 units ordered I
corrected that.
But today I received an email reminding me to pay you for the unit.
I have the
Hi
PHK has a roughly 6 line code snippet that does a basic PLL. Add two more lines
to check / clamp the integrator if you wish. That’s 8 lines. If you want a D
term (to give it an FLL component) add 2 more lines. We’re up to 10 lines.
It’s just a control loop, not a full GPSDO. There’s not a
Hi
The problem is that there are no “magic coefficients”. What you run depends
very much on the exact OCXO you have, the environment you run it in, and the
result you are after.
For instance, Bert is after frequency stability. Tom is after the right time.
Each of them will have very
Hi
The top of my list for “new NTP” would be to bring the 1588 hardware packet
time tagging into the NTP code base. There’s a pretty good base of hardware out
there that tags. It should help things on a loaded system.
Bob
On Oct 20, 2014, at 3:41 PM, Poul-Henning Kamp p...@phk.freebsd.dk
Paul,
I will answer you offline.
Guys please don't post items like this that aren't really of interest to all
the others on the list.
Thanks,
Said
Sent From iPhone
On Oct 20, 2014, at 13:41, paul swed paulsw...@gmail.com wrote:
Said
Having some fun reading your posts on time-nuts.
I
I absolutely did not intend to email time-nuts with my question on the
order.
I am embarrassed that happened and sorry everyone for the noise.
Regards
Paul
WB8TSL
___
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To unsubscribe, go to
Hello Jean-Louis,
unfortunately the 20MHz kits sold-out already so Ebay took down the page.
We only had 50pcs with 20MHz TCXOs. We are contacting the factory now to
see if we can get more on a quick turn.
Looks like instead of getting 50x 19.2MHz units we should have gotten more
20MHz
http://www.petermann-technik.com/products/rtc/ptrtc1010/
http://www.edn.com/electronics-products/other/4435988/Low-cost-real-time-clock-IC-offers-precise-timing
...Temperature stability is ±5 ppm within the -40°C to +85°C range,
which enables a highly accurate absolute time offset of 15
Allow me to clarify.
I started out with 7 MV 89 one of it a total loss. The remaining 6 after 3
month + burn in show better than 1 E-11 aging per day, 2 closer to 5 E-12.
Only two have been tested for ADEV and are close to 1 E-12, 2X not 10 X.
Bert Kehren
In a message dated 10/20/2014
Thanks much Charles,
just to remind everyone that the main idea of making the boards available
was to get folks a good disciplined TCXO, not to work as a development
platform to discipline external OCXOs.. Also as mentioned in the FAQ, the
typical performance plots I have been sending and
No worries, Paul. This was minor.
Actually, there have been quite a few postings in the past month that I suspect
went to the entire list instead of one recipient. It may have to do with the
recent changes to the mail list server (e.g., to accommodate AOL domains)? I'm
not really sure. It's
To add to Bert's note...
Realize that for a GPSDO, (linear frequency) aging-per-day is irreverent,
almost by definition. What matters is phase noise and short-term stability,
neither of which you can possibly fix with disciplining against GPS. GPS takes
care of the rest.
Long-term stability
here is the ADEV plot from my overnight test with the DOCXO. * * *
This was done without any loop adjustment whatsoever, same board and
software that drives the on-board TCXO. I will let the result speak
for itself,
save to say the loop, the DAC, the DAC reference, and the GPS with a
Hi Tom,
One of the biggest problems I've unwittingly faces is that of retrace. I had
seen the term used several times, but hadn't looked it up until last night. As
you can imagine, with a GPSDO under development I've had to remove power more
than a few times to make hardware changes. I
OK, Yahoo has done it to me again. Sent to Tom direct and not to the list.
So, repeated here:
Hi Tom,
One of the biggest problems I've unwittingly faces is that of retrace. I
had seen the term used several times, but hadn't looked it up until last night.
As you can imagine, with a GPSDO
Bob,
You are on the right track!
Large changes in EFC can cause hysteresis, meaning you go back to an initial
voltage but the crystal does not return to the exact initial frequency. It can
also create dead bands in the efc vs frequency curve.
Hysteresis can cause integrator wind up as the
Hi Said,
OK, I hadn't understood the full consequences of hysteresis, but yes, I've seen
it. For an hour the DAC ratchets up a step every few minutes and the phase
stubbornly stays put. And then, the bottom falls out and it suddenly pushes
way past where you want it. Well, at least I have a
Thats exactly right Bob.
By the time your ocxo jumps to catch up to the efc voltage, you have
oversteered, then the process starts in reverse and the ocxo jumps in the
opposite direction.
The result is a phase jumping up and down.
You want a crystal that reacts to xE-012 changes in EFC
Skip Withrow contacted me and explained that apparently the FE5650 has a
tendency to get it's internal EEPROM corrupted when sending commands to it
right after power up. This confirms my suspicion that the EEPROM of my
FE5680A unit suffered the same fate.
He offered me to reprogram the unit as he
What does everyone think of this GPS module for ntp use? According to the
specsheet, it uses a Ublox Neo-7N.
http://www.ebay.com/itm/RY725AI-10Hz-UART-USB-interface-GPS-Glonass-QZSS-antenna-module-flash-memory-/181562403752
I'm thinking about using it for a Beaglebone ntp server. I know there
Hi
Unless we are talking about flash rather than EEPROM, an image may not do you
much good.
Firmware normally gets stored in flash. That code is at least similar from unit
to unit.
Calibration data normally gets stored in EEPROM. On a modern Rb there are a lot
of things that are “tweaked”
Hi
There is a *lot* of detail on this in the archives.
Quick rundown - the Soekris has some custom code and “stuff” that makes it
better for NTP than any of the other boards.
For any normal use, a couple of microseconds is likely “good enough. For that,
many boards and GPS’s will do just
The one thing that hasn't yet happened is making the beaglebone timestamp
on the linux side in a way that works for ntp.
Custom code no problem. Freebsd PPSAPI no problem. Linux, nothing there
yet.
I have been working on it but if anyone has some insight its appreciated.
On Monday, October 20,
NTP is not nearly good enough to use for measuring speed of light
delays. It works at the microsecond level at best. I think what you
want is each station to have a local oscillator that runs in phase
with the 1PPS signal that comes from GPS receivers. Then you measure
the incoming signal
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