paul swed writes:
> Hello to the group its time for a wwvb chronverter update. I used the loop
> antenna as Alex suggested. I added caps to resonate it sort of.
I am still a bit puzzled by this desire to feed the time in via LF
waves. Maybe WWVB clocks are more different from the MSF / DCF77
paul swed writes:
> Indeed anything could be used if you want to modify the clocks. I
> don't.
Fair enough.
> They do what they do very well and consume 0 power.
Well, I assume there's some sort of battery involved, but anyway, this
line of discussion misses the point. Replacing one LF module
Matthew D'Asaro writes:
> The concrete block is a generic 1 sqft paver stone which cost all
> of $1.18. This is to provide a heavy base and avoid tipping.
If you want to keep your roof undamaged, you need padding under that
concrete block (some geotextile sheet plus perhaps a bit of rubber
Attila Kinali writes:
> Yes. This effect has been known for a few decades at least. What kind
> of puzzles me is, that I have not seen a mathematically sound
> explanation of it, so far.
I'm afraid I can't help with the rigor, but the fundamentals seem simple
enough to me.
> People talk of
Am 02.01.2019 um 12:49 schrieb Chris Burford:
I'll give the window placement a try and see if I can maintain a usable lock.
If you're using a patch or puck antenna, putting a ground plane under it
can work wonders (I've seen 15dB gain in one particular case). I've
been using larger cans to
Charles Wyble wrote:
> I’m using a raspberry pi with gps hat for my master time source.
> Shortly I’ll be having a total of three systems (two using the same
> hat, one using the adafruit hat and being a pi2). I’ve got some
> interest in multiple way comparison and will follow this thread
>
Charles Wyble wrote:
I built a dedicated server room in my house, with it's own air
conditioner. I've been working on overall instrumentation , especially
temperature.
If the rasPi is a dedicated system and does not serve extra tasks, just
record its CPU temperature, no extra sensor needed.
Gerhard Hoffmann writes:
> Have you seen the new THS3491 ? LMH6702 on steroids.
>
> This one begs to be designed into new distribution amplifiers:
>
> Everything from DC / 1pps to a few 100 MHz into 50 Ohms, without any
> changes.
While everybody is looking for opamps with even higher GBW
Bob kb8tq writes:
> It would be nice to see an ADEV plot if indeed GPSDO use is a target market.
The common datasheet for this part only seems to tabulate the phase
noise specs, but the SiT5356 datasheet has actual ADEV/TDEV plots. For
both series there are companion documents for the more
Poul-Henning Kamp writes:
> The TODO point is to take a RaspBerry Pi, run a tight loop with all
> which wiggles a GPIO pin with all interrupts disabled, and measure
> the phase noise.
You'll quickly find out that the ARM part of the BCM SoC is not fully in
command. The VC4 GPU is calling all the
Tobias Pluess writes:
> I once tried to use the internal PLL of the microcontroller to boost
> the OCXO frequency to the max. 72 MHz which my microcontroller
> accepts. While this would greatly increase the frequency measurement
> resolution, it decreased stability because it appeared that the PLL
Joe Hobart writes:
> Your accuracy results are impressive. I have questions:
>
>What manufacture or brand DS3231 do you have?
There are two modules you can get easily from the usual places, prices
and delivery times vary wildly. The first and larger variant used to be
called ZS-042, but now
jimlux writes:
> Here's the application:
> 100 (or 1000) independent nodes (in space, as it happens) - I want to
> calculate the probability that two nodes are within some delta f of
> each other.
Provided I get correctly what you are trying to do: perhaps it would be
easier to take one of the
Tobias Pluess writes:
> I was reading on this list for quite a while, but still have some
> questions I'd like to ask. Please forgive me my perhaps silly
> questions since I am a newbie to the timenuts world :-)
>
> So I have built my own GPSDO. I used a low phase noise OCXO from
> AXTAL, a
Steve Olney writes:
> I think the level of precision you guys are aiming for is massive
> over-kill for my application. Holding +/- 1 us over 15 minutes would
> be a doddle by many means as has been mentioned by you guys. I just
> wanted to know whether the basic GPS mouse PPS would stay
Tobias Pluess writes:
> By the way, this is the unit I built:
>
> https://hb9fsx.ch/wordpress/index.php/2018/11/14/my-own-gpsdo-part-i/
Nice build. Minor nit: Whatever foam you used to isolate your OCXO
further is probably not SAGEX, but looks to be either cross-linked PE
foam or (more likely)
Joe Hobart writes:
> I can read and write the DS3231 registers with a Raspberry Pi. Unfortunately,
> the RPi kernel sends time to the RTC every 11 1/2 minutes. This time is
> usually
> moderately accurate, but I have measured errors of up to 0.264 second, which
> is
> unacceptable.
That's the
Mark Sims writes:
> For all the receivers that I have tested there is only one combination
> that jumps out as being the correct one. However, for the new Ublox
> F9P, there are two combinations that produce virtually identical
> measurements and statistics (add current sawtooth or subtract
Bob kb8tq writes:
> It’s just like the other uBlox modules (and just like the F9T …) the external
> input is a once a second time stamper with an 8 ns resolution (just like the
> +/- 4 ns on the sawtooth ….).
A minor nit: If it works as the M8 series does (which is very likely),
the timestamp
Bob kb8tq writes:
> The first one is designed to mount on a ground plane (which is fine if it is
> going
> on a truck or airplane). It also is a bit low in gain for what I *think* the
> F9 is looking
> for.
The only antenna that u-Blox themselves advertise for use with the
(eval) F9P module
Hal Murray writes:
> kb8tq-wyfad0z3...@public.gmane.org said:
>> The first one is designed to mount on a ground plane (which is fine if it is
>> going on a truck or airplane).
>
> How big a ground plane do they need? I'm thinking of a sheet of aluminum.
Typically if they already have a ground
Denny Page via time-nuts writes:
> Thanks Mark. For the cost, this seems like a worthwhile thing to
> try. I don’t think the homeowners association would be too thrilled
> about a pizza pan on a pole so I’ll probably have to do without.
Use a resonant ground plane with four or eight tuned radials
Achim Gratz writes:
>> If it's any good, buy a Pi-Zero, rip out the X-tal and feed it
>> from your LPRO instead. If you only need one GPIO pin, I doubt
>> the exact clock frequency matters much.
>
> I still want to use a GPS timing module and feed the 19.2MHz in from
>
[typo in subject corrected]
John Ackermann N8UR writes:
> On 2/3/19 11:48 AM, Achim Gratz wrote:
> I've been playing with the SiLabs 53xx series chips. There are two
> that are quite interesting for time-nuts.
I am really trying to go for the octal output parts. :-)
I'd r
Tim Shoppa writes:
> I have been observing time.cloudflare.com latency and accuracy the past 3
> days.
>From my home network it is actually pretty bad compared to some other
servers. It's likely the network and not the server, though.
> It is a stratum 3 server, so folks might think that it's
Denny Page via time-nuts writes:
> No, no ground plane. Don’t really have a lot of room for that in the
> window. Out of curiosity, how large of an impact have you found with a
> ground plane?
As long as we're talking ceramic patch (puck) antennas, I've seen around
15dB improvement repeatedly (as
Glen English VK1XX writes:
> Has anyone tried to use a Neural net to control oven tmep, rather than
> the ye olde PID ?
If you believe the marketing, that is why the Nest thermostat is
connected to the cloud.
> IE the algorithm learns from previous beheviour and successfully
> predicts behaviour
Leo Bodnar writes:
> Correction on all Ublox receivers including F9P is done at navigation
> rate which can be set as high as 20Hz.
If you are thinking of the sawtooth correction, then I think you'll find
that this is only available for the full second. There is some mumbling
in the manual that
Glen English VK1XX writes:
> My intention is to use the average of multiple stationary mode GPS
> 1PPS signals to drive a single OCXO, the idea to be a better 1pps
> estimate. I'll upsample the inputs to get the control sample rate up.
I'd expect a lot of correlation among multiple GPS receivers,
Adam Kumiszcza writes:
> After all your tips I just checked whether the roof itself blocks the
> signal or not. I put the patch antenna together with a metal disk on top of
> a high wardrobe, close to ceiling, and I guess it is the best position
> here. See attached screenshots.
Good, that looks
Adam Kumiszcza writes:
> I've made a ca. 10.5 cm metal disc cut from an old car radio chasis and put
> it under my gps antenna. It does not hang now, but lays on the window sill,
> facing up.
That way you changed three variables in one go. You'd be better off
changing one single thing each time
Adam Kumiszcza writes:
>> The key here is to have some conducting magnetic material under the
>> antenna, not just sitting on its own.
>
> My GPS antenna hangs on the window handle and still gives the good result.
> It's on the south facing window. Unfortunately, in the new location I will
> have
Achim Gratz writes:
> The thing to note is that you need to boot with "nohz=off",
Tom was asking what that kernel parameter meant and does.
UNIX used to have a fixed frequency interrupt called TICK that would do
its thing HZ times per second (typically HZ=100, but later on HZ
wildylion via time-nuts writes:
> The point is: do we ever need S1 NTPs? I think, this could be a nice
> addition if properly realized, but right now I'm not sure if I can
> propose it.
You really can't properly monitor any stratum-2 sources you have
configured if you don't have your own
Tim Shoppa writes:
> Real ntpd uses a drift file to track the local processor's frequency offset
> and has a good estimate of processor clock drift after a day of tracking.
That assumes stable median temperature and predictable temperature
swings.
> The Raspberry Pi processor clock, like any
wildylion via time-nuts writes:
> Situation 1:
> What I currently have is a uBlox M8N GPS puck I'm planning to use with
> the Raspberry PI. Seems like it should work almost out of the box with
> some kernel tuning, but I have a question about short term stability
> in the event of GPS loss - how
Paul Theodoropoulos via time-nuts writes:
> I've also found that my Raspi's give the best results with board temp
> right around 60°C. However, I found that the 'CPU as heater', while it
> does help dramatically compared to nothing at all, it introduces a lot
> of jitter on its own. Much better
Richard Laager writes:
> I stumbled across this product listing:
> https://www.teradak.com/products/115.html
That site red-zones my BS detector…
> It's a Pi hat that contains two TCXOs, one at 19.2 MHz for the CPU and
> one at 25 MHz for the Ethernet controller.
The one for the Ethernet
Richard Laager writes:
> How would it work to have two crystals connected in parallel?
Not two crystals in parallel, a crystal plus the output of an (external)
reference oscillator. If the two frequencies are close enough you can
injection lock the crystal oscillator, but the more likely outcome
ed breya writes:
> I think the main need for the overall DAC system in these is not
> linearity, but monotonicity - an increasing digital input always
> causes an output change in one direction only, and never reverses.
An y=x³ (cubic) transfer function is monotonic but not linear, yet you
Attila Kinali writes:
> There is, as far as I know, only two types of DA converters that
> are inherently linear: single-bit delta-sigma modulators and
> Kelvin-Varley dividers.
No, the Kelvin-Varley is not guaranteed to be linear, same story as a
string DAC actually. Whether a delta-sigma
folkert writes:
> For fun I hooked up a TCXO to an Arduino. That Arduino then interfaces
> the TCXO to the I2C in the VGA connector and then with some magic code,
> it syncs the PPS signal to NTP.
> https://vanheusden.com/misc/blog/2019-11-07.php
On an actual VGA connector one of the monitor ID
David J Taylor via time-nuts writes:
> The graph in ntpviz shows the jitter and temp almost perfectly correlated.
Based on my experience it should really be a correlation of temperature
rate of change vs. jitter. On my self-ovenized servers I see on average
around 200ns jitter (close to the
John Ackermann N8UR writes:
> One related question, especially with mixed systems -- how do you tell
> if you have optimum signal level at the receiver?
I don't think you're going to figure out an _optimum_ gain without
proper measurements along the whole signal chain. As a proxy, the
reported
Fiorenzo Cattaneo writes:
> I have been quite puzzled about the asymmetric nature of my home Cable
> Modem connection to the Internet in regard with the offset discrepancy
> I observe. The "last mile" asymmetric nature of Cable Modem (Comcast
> in my case) is not very high compared the delta I see
Tobias Pluess writes:
> Assume a timer is clocked with the 10MHz clock. The timer overflows
> when it reaches 999 (=10e6-1). Further, this timer is used to
> generate the 1PPS pulse output: each time when the timer reaches the
> value of 0, a pulse is generated on one of the output pins. Since
Adrian Godwin writes:
> Off-the-wall thought : could you discipline a well-insulated raspberry pi
> to NTP using heaters or workload to modify its temperature ?
Yes you can, been doing that with four rasPi and two TinkerBoards for
quite a while now to run the XTAL at its turnover temperature
Am 22.12.2019 um 20:37 schrieb Taka Kamiya via time-nuts:
> Most commercially manufactured time and frequency sources use
> switching power supply.
[...]
The suggestion to "just use a linear power supply", especially if it was
designed some decades ago is probably not getting the desired
Am 23.12.2019 um 16:03 schrieb jimlux:
It is tough to build a "small" input filter that has good rejection at
low frequencies (<100kHz?)
Yes if you want a passive filter, but you can view an LDO as an active
low-pass in some sense. Again you need to take care that noise cannot
bypass it,
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