On 04/26/2014 02:27 PM, Laszlo Hanyecz wrote:
It's fine to disable the additional cores/cpus on a dedicated NTP machine, but
I wonder if there is a solution that allows both the TSC and all the cores to
be used at the same time. Is it even possible to completely sync the counters
across CPUs
On 04/10/2014 05:38 PM, Hal Murray wrote:
Does anybody have a favorite low-cost ARM board? I'm looking for a simple
Arduino like setup rather than something that runs Linux. The idea is to get
32 bit counters so a bunch of the recent discussion can be ingnored.
Another endorsement for a
On 9/9/2013 11:08, Paul wrote:
Although the inexpensive yet high sensitivity units are nice I'm not
sure why someone would choose a positioning MTK (e.g. Adafruit) over a
timing Ublox (or even an old Motorola style timing receiver).
Am I missing something?
In a word, availability. Try buying
On 5/29/2013 12:11, Robert Darlington wrote:
I ordered two PoE clocks, one with the 12 hour face, one with the 24 hour
face.Earlier this week I considered using the Vetenari Clock project
circuit board to control a cheap analog clock movement and have it do my
bididng -however I can't write
On 05/02/2013 03:26 PM, Paul wrote:
Is it reasonable to to use a GPS distribution amplifier (viz. HP
58516A) to power a five volt antenna feeding three volt receivers or
should I get a bias tee? The internal operation of my electronics
is largely a mystery to me.
Bias tee would be best
On 5/1/2013 11:40, Sarah White wrote:
I tweeted the author of this article, trying to point out that (as I
understand) radioactive decay is not relevant in any way for cesium
frequency standard/reference thingies:
https://twitter.com/kuzetsa/status/329618223916011520
If someone more
On 3/13/2013 13:15, Azelio Boriani wrote:
Then you will start to
appreciate things that will lead you to a timing receiver with the sawtooth
correction.
For what it's worth: I have been evaluating the NEO-6M, a navigation
receiver, for use in a NTP server which I have posted here in the past.
On 03/13/2013 09:05 PM, David wrote:
This brings up something that I have wondered about for a while.
The Garmin GPS18x (and many other receivers) specify the PPS output as
within 1uS but does that mean it wanders around over say 12 or 24
hours within 1uS of GPS Time or does it mean something
On 02/10/2013 11:22 AM, Chris Albertson wrote:
Yes there is a standard but there are also may non-standard implementations.
I was a little worried about the comment regarding isolation being
hard to implement. The standard for Ethernet required galvanic
isolation on all Ethernet ports by use
Greetings time-nuts,
I've finally gotten the software for my NTP server project to the point
where I'm comfortable shipping the boards I have now, so it's about time
to spin the next revision. If you could take a minute to look over the
feature list and let me know on- or off-list what you'd
On 02/09/2013 08:35 PM, Chris Albertson wrote:
Features?
1) Power the thing with power over Ethernet then you can remove the
coaxial power input. Also this would make it real easy to place the
server right at the antenna location. You would simply run cat-5 up
to the roof. The mount the
On 02/04/2013 05:09 PM, Stanley wrote:
If a fiber-optic cable had temperature sensors either installed with or
embedded inside of this could make for better modeling changes in delay making
more accurate transfer of time and frequency possible. With fiber to tower
installs now under way to
On 1/21/2013 10:26, Rob Kimberley wrote:
http://www.electronicsweekly.com/Articles/28/09/2012/54676/raspberry-pi-gets
-a-competitor.htm
Olimex is also making an A10 board with sound industrial design, to be
available in the near future. The advantage here for time-nuts is that
the A10
On 01/02/2013 08:34 PM, Tom Harris wrote:
Do you really need an OS? Surely for a box that is only ever going to be an
NTP server you just need a network interface and good maths? I've just seen
a later comment where you mention floating point support, but would 64 bit
integer maths work just as
On 12/28/2012 12:34 PM, Chris Albertson wrote:
One idea that I like is to first get a large FPGA. Then you load in a
soft CPU and then you run an OS and NTP on the soft CPU. Inside
the softCPU the counter is implemented like it is in a real CPU but
you can add the ability for a PPS to latch
On 12/27/2012 01:41 AM, Michael Tharp wrote:
The good news is that the disciplining algorithm I lifted from my
previous GPSDO project works quite well, and I have the gritty details
of measuring the PPS worked out. If I can get the Trimble working
tomorrow I might have much better results soon
On 12/26/2012 12:01 PM, Chris Albertson wrote:
The VXCO quality hardly matters for an NTP server. As long as it
does not gain out loose more then 1 uSecond per second. In other
words one part per million is fine for NTP. The goal is not to
produce a 10MHz GDPDO. Clients using this server
Hello and Merry Christmas,
I made an embedded (S)NTP server. The software is still under
development and will eventually include a low-grade GPSDO but right now
even the simplistic algorithm is working quite well so I figured I'd share.
On 12/25/2012 02:51 PM, David J Taylor wrote:
I think you should be able to do better on the jitter as your algorithms
develop.
Yes, for starters something is causing a silly amount of extra latency
hence the 2.4ms round-trip. I managed to cut that in half by changing
compiler options but
On 12/6/2012 4:26 AM, Fabio Eboli wrote:
Here are the design documents, if you're curious:
http://hg.partiallystapled.com/circuits/serafine/raw-file/d75ab09ca163/out/production.PDF
Thank you very much, I will study it with interest,
it will be very helpul to see what you have done.
Can I ask
On 12/05/2012 08:03 AM, Fabio Eboli wrote:
I'm seriously thinking to attempt a gpsdo.
It's mainly to learn something new.
For some reason I collected some Rb oscillators,
and I'd like to have a 10MHz absolute reference,
so I will try to discipline one of the Rb, and
later maybe an OCXO.
The
On 11/21/2012 06:58 AM, Magnus Danielson wrote:
It was a common mode error to both servers. It's worth nothing that even
a high-ranked clock house like USNO can have these errors so trusting
the one and true server can fail greatly. NTP by it's design has methods
to handle these kind of errors
On 11/21/2012 06:24 AM, David J Taylor wrote:
I only use gpsd on the Linux system, and then only because it was the
first thing I discovered when searching with Google. As the precise
timing is from the PPS signal fed to the GPIO pin, with a GPIO interrupt
handler, I am forced to use that. I
On 11/03/2012 05:05 AM, Sarah White wrote:
Seeing as I'm in the process of installing a hardware refclock (trimble
thunderbolt connected via serial port) for my NTP, it is highly
problematic and potentially error-prone for microsoft's OS to touch the
bios hardware clock AT ALL.
Just in case it
On 10/16/2012 05:06 PM, x...@darksmile.net wrote:
My goal is to design a custom board for the Pi and mount a GPS receiver
on it. With this combination, I should be able to configure NTP for the
Pi and thus have the Pi act as a Stratum 1 NTP server.
The new RasberryPI has 512MB memory so it
On 10/16/2012 06:28 PM, sh...@impsec.net wrote:
I'm a junior time-nut at best but it looks to me like jitter from the
USB Ethernet is acceptably low, based on ntpq -p anyway:
It's a minor problem at worst. There are many worse conflating factors
and NTP adjusts very slowly anyway to deal with
On 10/10/2012 11:49 AM, Bob Camp wrote:
No easy solution. Serial com is still with us because it's a lowest common
denominator. I'm sitting here coding it into a new product right now (once
the uber super compiler finishes a build). It's supported on just about
every chip set in the universe. I
On 10/02/2012 10:37 PM, Jim Lux wrote:
Intriguing.. Can it handle the Doppler, etc., for a cubesat in LEO?
(7km/s) The total Doppler isn't usually the issue (the GPS satellites
are moving faster, after all), but the receiver may not work for high
velocities, high altitudes?
GPS receivers that
Greetings nuts,
I've been working on a simple GPSDO as a starting point for further
experimentation. I'm using a STM32 microcontroller running at 72MHz as
the heart, with the input capture peripheral comparing the phase of the
pulses-per-second and a 16 bit PWM DAC to drive the VFC. It's all
On 09/14/2012 05:31 PM, Chris Albertson wrote:
Michael: Actually implementing a 16 bit DAC to its 1-bit minimum
resolution will be headache enough. You will gain a real education in
good grounding practice, shielding, power supply stability and noise,
and other Murphy intrusion. A 32 bit DAC
On 09/10/2012 06:36 PM, Bob Smither wrote:
May not be redundant for time nuts! I have an NTP client on my Android and it
shows the network time (Sprint in my case) is often as much as 2 seconds behind
UTC.
Anyone else noticed this?
It may not really be using network time, or not using it
On 09/05/2012 12:46 PM, Bob Camp wrote:
Hi
There are a number of discrete transistor buffers that have very good
isolation and short term stability / phase noise performance. I'd take a
look at the one from the NIST papers and Bruce's more modern re-design. All
are in the archives.
On 08/27/2012 10:09 AM, Jerry wrote:
Are these thermal pads temp conductive or insulative? If you want heat
dissipation why not use the readily available thermal grease used for
semiconductor mounting? Cheap and not really messy if applied correctly
A layer of Kapton (polyimide) tape would be
On 08/22/2012 01:22 AM, Edgardo Molina wrote:
b. Is it possible to build a GPSDRb? I would like to know if it is reasonable
to pursue the goal to discipline the 5065a with a TB which I also got recently.
Some Rbs have a C-field input that can technically be used to
discipline it, but this is
On 08/21/2012 12:35 PM, Sarah White wrote:
Thanks Chris.
I always appreciate clear explanations. I'm assuming that the fixed
location requirement is important to note for purposes of compensating
for any dopler shift, as well as the distance the signal must first
travel before being decoded.
Greetings nuts,
All this recent NTP discussion has me thinking about a dedicated NTP
server again. The usual solution is to use commodity hardware of some
persuasion (PC, mini-itx or even ARM) running ntpd, but I'm thinking we
can do better. The only reason a full ntpd is needed is for its
On 08/19/2012 01:38 PM, Chris Albertson wrote:
NTP is not as easy as you think. Just doing the cryptography to handle
authentication is more then I would want to write. When a free open source
ntpd exists it will be really hard to get people to help work on
re-inventing it. But your idea to
On 08/19/2012 03:38 PM, Christopher Brown wrote:
Though I am a little surprised about residential power being
measured/billed in VA not KW/h in North America. Pretty sure the US is
in North America, even Alaska in slightly more North America. Never
seen a VA/h meter in the US.
Was guessing it
On 08/06/2012 12:57 PM, Miguel Barbosa Gonçalves wrote:
Hi!
I'm looking at the Resolution T from Trimble
(http://www.trimble.com/timing/resolution-t.aspx).
Does anyone here connected it successfully to a computer?
Are the voltages compatible with RS232 or do I need some converter?
It is
On 07/19/2012 07:36 PM, Al Wolfe wrote:
Chris,
The simplest zero crossing detector would be to feed your 1 volt, 10
mHz from the XL-DC into the input of an IC with schmidt trigger inputs.
You would need to provide a series coupling cap and probably some DC
bias from a pot to adjust symmetry
On 06/25/2012 09:37 AM, Erno Peres wrote:
Hi David,
thanks a lot for the info, I have also the 1PPS output, but had the
impression that it will also output TSIP or any other kind of MSG upon
power-up... and you can configure the board as required of the need.it
outputs according to
On 06/05/2012 11:03 AM, Peter Monta wrote:
I've been working on a front-end board suitable for GPS and other GNSS
systems. It might be of interest to time-nuts given the application
to timing receivers.
Very impressive. Since I discovered time-nuts this is exactly what I
wanted to make, and
On 06/05/2012 03:31 PM, Attila Kinali wrote:
* The XC6SLX9 is10USD more expensive than the SLX6. I think the added
value of having twice as much real estate would justify the additional
price.
Some vendors don't even stock the SLX6, including Digi-Key! Agreed
though, it would be neat if
Greetings,
I've been pondering topologies for a custom GPSDO design and two obvious
choices seem to present themselves. The first, and seemingly more
popular by far, is to use a pullable oscillator as many OCXO and Rb
oscillators are and discipline it using a slow but precise DAC. But
On 05/27/2012 06:23 PM, Bruce Griffiths wrote:
The principal problem with conventional DDS implementations is phase
truncation spurs which can occur close to the desired carrier.
Virtually all commercial DDS chips produce such phase truncation spurs.
It is possible to eliminate such spurs if
On 05/27/2012 07:10 PM, Magnus Danielson wrote:
How far off? What Rb do you have?
Most Rb:s not having a EFC input should be possible to modify for EFC in
one way or another, since the C-field needs to be applied regardless.
I don't know how far off it is. It's an Efratom 102100-001, which
On 05/22/2012 06:37 PM, Pete Lancashire wrote:
I've never though about using one to distribute the 1PPS for NTP. Its
a pity there isn't enough umph inside one of these
little Linux boxes to implement NTP.
Don't get too excited because this is many months out, but I'm working
towards designing
On 05/18/2012 08:24 AM, Bob Camp wrote:
Hi
For a 50 ohm buffer, you probably want something like 200 ohms in series
with each output (4 buffers) or 400 ohms (8 buffers).
Yep, I ended up choosing a quad buffer with 180 ohms on each pin which
should yield 45 ohm source impedance and 27mA
On 05/18/2012 01:33 PM, Mark Sims wrote:
While you're at it, add an ATMEGA328 processor and a 250 ps res/256 step delay
line. The processor reads the timing message, picks off the sawtooth
correction factor, converts it to an 8-bit value that it output on a port to
the delay line. The
Greetings,
As I mentioned briefly a few days ago I'm working on an interface board
for the Trimble Resolution SMT carrier board to provide a convenient way
to get power in and PPS/serial out. The PPS output is a 3.3v, 125
microsecond long pulse and I'd like to buffer it with something that
On 05/14/2012 09:11 PM, Mark Sims wrote:
Attached is a Lady Heather screen dump of a Trimble Resolution-SMT timing
receiver behaving badly. The first quarter of the plot the unit was tracking
all sats above 0 degrees/0 dBc. The next quarter the masks were set to 30
degrees/30 dBc. Then
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