On Thu, Aug 8, 2019 at 8:07 AM Adam Kumiszcza akumiszcza@gmail.com wrote:

EndRun Technologies
(https://endruntechnologies.com/products/grandmaster-clocks/ptp-slaves)
make mention of a Windows PTP slave - not sure if it's the same
version you have found. It does also make mention of the fact that
precision is limited on Windows depending on version although from
what I gather from the satsignal.eu that precious on Windows improved
with 7 or later.

For deterministic timing I think it has to be Ethernet and as outlined
in their white paper (https://endruntechnologies.com/pdf/PTP-1588.pdf)
it works best if you have hardware timestamping in the NICs at each
end and IEEE1588 compatible network switches (and even when the claim
to support it, apparently they don't always do it properly:
https://www.linkedin.com/pulse/ptp-support-high-end-ethernet-switches-heiko-gerstung).
You may be able to do some Pi-to-Windows PTP experiments with a
crossover cable. Not sure if the Pi has the hardware timestamping,
seems unlikely given the low cost of the Pi's as in the 3B+ (and below
I believe) the Ethernet is provided by a combined Ethernet/USB2 hub
and limited by the speed of the USB2.

NTP works best if the network delay is symmetric and stable - this
would also rule against wlan I'm afraid.

act as the "grandmaster" without having to buy an expensive external
grandmaster clock (the ones I've seen from e.g. Microsemi, Brandywine,
Meinberg etc are of the "Get a quote" variety which tends to mean
"expensive")

Cheers,
Tim

On Thu, Aug 8, 2019 at 7:00 PM David J Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:

First of all, thank you for the info you put on satsignal.eu org! I've used
some of these in the initial configuration of my server.

By feeding PPS signal to the Windows PC you mean adding cards or connecting
boards (like Sure Electronics GPS evaluation boards) to Windows computers?
My idea was to lower the time offset of machines connected by LAN to a
single stratum-1 server. But maybe I'll come to that later.

Out of your monitored servers on
https://www.satsignal.eu/mrtg/performance_ntp.php I am amazed by
performance of LeoNTP box. What do you mean by indoor antenna here?

Best regards,
Adam

On Thu, Aug 8, 2019 at 7:01 PM Tim Lister listertim@gmail.com wrote:

It's additional software here. As far as I understand, recent Windows 10
versions introduced under-the-hood internal implementation of PTPv2, with
kernel support for it.

Pi 3B+ has only software timestamping, and even this is not completely
clear (I had to patch the kernel). Pi-to-Windows direct crossover testing
is a great idea!

Best regards,
Adam

On Thu, Aug 8, 2019 at 4:07 PM Adam Kumiszcza akumiszcza@gmail.com wrote:

Although there is one method using WSL, there is also the "native" method
https://techcommunity.microsoft.com/t5/Networking-Blog/Top-10-Networking-Features-in-Windows-Server-2019-10-Accurate/ba-p/339739
"Precision Time Protocol - Try it out!"

PTP can be used across any IP network, but if there is non deterministic
latency (jitter), there is a fairly obvious effect.

The offset should reduce over time, but jitter will affect this.

I've already tried setting PTP on the Raspberry Pi 3B+. It needed a kernel

I have run PTP on a rPi 3B without any kernel modifications as a
grandmaster (with a ublox GPS to provide time and PPS), and experimented
with different NICs (intel, broadcom and solarflare, all with HW
timestamping) as clients in x64 hosts.

There are two issues with using a rPi as a PTP grandmaster, the crystal is
"not very stable", and the NIC is connected over USB, both of these add
jitter which is noticeable on PTP. The jjitter is obvious when compared to
a meinberg m600 with the HQ OXCO option.connected to a Solarflare NIC in a
Linux host.

To remove the jitter issues, you might care to try the ublox connected (via
a suitable level converter for NMEA and PPS) to a hardware serial port on a
Linux X64 host.

I have not tried the native Windows PTP client, there are also 3rd party
clients from greyware and fsmlabs.

On Fri, Aug 9, 2019 at 1:01 PM shouldbe q931 shouldbeq931@gmail.com wrote:

Thanks! The link at the bottom is to a .doc file, which gives some
explanations. I'll try it out more thoroghly later. (
https://aka.ms/PTPValidation).

Some of the required links do not work, though, so it all seems a long way
till stable I guess.

I have run PTP on a rPi 3B without any kernel modifications as a

What type of PTP did you use? ptpd (https://github.com/ptpd/ptpd) or
linuxptp (http://linuxptp.sourceforge.net/)?

I've tried the latter, and used the following ntp.conf (part of it here):

#PPS Kernel mode
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 time1 +0.000000 flag3 0 refid PPS

tos mindist 0.002

#GPS (NMEA)
server 127.127.20.0 mode 89 minpoll 4 maxpoll 4 iburst prefer
fudge 127.127.20.0 flag1 0 flag3 0 time2 0.059089 refid GPS stratum 2

#local PTP reference
server 127.127.28.0
fudge 127.127.28.0 refid PTP

/etc/linuxptp/ptp4l.conf has the following lines:
clock_servo            ntpshm
ntpshm_segment          0
priority1              10
priority2              10

(the rest was left as default)

/etc/linuxptp/timemaster.conf is as follows:

Configuration file for timemaster

[ntp_server localhost]
minpoll 4
maxpoll 4

[ptp_domain 0]
interfaces eth0
delay 10e-6

[timemaster]
ntp_program ntpd

[chrony.conf]
include /etc/chrony.conf

[ntp.conf]
includefile /etc/ntp.conf

[ptp4l.conf]

[chronyd]
path /usr/sbin/chronyd

[ntpd]
path /usr/sbin/ntpd
options -u ntp:ntp -g

[phc2sys]
path /usr/sbin/phc2sys

[ptp4l]
path /usr/sbin/ptp4l

But I think this shows it does not really interact with ntp:
pi@zegar:~ $ ntpq -c "cv &3"
associd=52436 status=00f1 15 events, clk_no_reply,
device="SHM/Shared memory interface", timecode=, poll=1850, noreply=1850,
badformat=0, baddata=0, stratum=0, refid=PTP, flags=0

(maybe because there's nothing connected on the other side, but I guess
noreply means no reply from PTP daemon?)

Best regards,
Adam

On Sat, Aug 10, 2019 at 9:02 AM Adam Kumiszcza akumiszcza@gmail.com wrote:

I've not tried it yet, the links all worked for me. In case it is a setting
in your word viewer, I have saved it as a PDF (attached)

I used ptpd

The ntp.conf should take the NMEA feed (as "wall clock" time) and PPS.for
precise time, and ideally a connection from other NTP servers to ensure
that the NMEA feed is "sane" If the host is also running as a PTP GM, it
should not be feeding PTP time (that it is generating) back into NTP.

I ran ntp (ntpsec) fed from gpsd for time and PPS, and then just ran ptpd
as a GM, taking its time from the "trained" (by ntp) clock on the rPi

/etc/linuxptp/timemaster.conf is as follows:

native full speed Ethernet interface, not through USB.
I also read that it needs a heat sink.

Didier KO4BB

On Fri, Aug 9, 2019 at 6:04 PM David J Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:

I will try that. I guess you can connect serial port directly to my
Uputronics expansion card (
https://store.uputronics.com/index.php?route=product/product&path=60_64&product_id=81)
while still attached to Raspberry Pi. Problem is, I'm a software, not a
hardware guy. No idea about soldering. Time to learn a new skill :)

If the PC doesn't have a serial port, check on the motherboard because

That's exactly in my case. Motherboard manual says the serial port
expansion is sold separately.

[..] Check with your Android mobile phone

I don't have access to any Android device :( I'll try to use gpsmon or
other tool to check GPS signal level (S/N ratio of satellites should be
sufficient, I guess?).

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 access only to west facing window.
Why is it good to have some conducting magnetic material under the antenna?
Is it to reduce multipath?

Best regards,
Adam

Adam Kumiszcza writes:

You should orient it correctly so that it is facing up, not simply
dangling it from the cable.  GPS antennas are directional.

The GPS dielectric patch antennas are designed to perform best with a
ground plane.  The optimum size varies a bit, but between 10…14cm in
diameter is about right.  The ground plane does normally not need to
connect to anything, it has to be conductive but not necessarily
magnetic (aluminum foil is OK, too).  If you have a magnetic puck
antenna, then using a magnetic surface has the advantage of the antenna
staying in place more easily, though (try the bottom of a large can of
vegetables).  If you are unsure how large your ground plane really needs
to be, just use one of the programs that visualize the signal strength
on each sat in view and optimize for highest level over the visible part
of the sky, but especially the higher elevations (sats directly above
you).

Regards,
Achim.

+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Wavetables for the Waldorf Blofeld:
http://Synth.Stromeko.net/Downloads.html#BlofeldUserWavetables

I will try that. I guess you can connect serial port directly to my
Uputronics expansion card (
https://store.uputronics.com/index.php?route=product/product&path=60_64&product_id=81)
while still attached to Raspberry Pi. Problem is, I'm a software, not a
hardware guy. No idea about soldering. Time to learn a new skill :)

If the PC doesn't have a serial port, check on the motherboard because

That's exactly in my case. Motherboard manual says the serial port
expansion is sold separately.

[..] Check with your Android mobile phone

I don't have access to any Android device :( I'll try to use gpsmon or
other tool to check GPS signal level (S/N ratio of satellites should be
sufficient, I guess?).

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 access only to west facing window.
Why is it good to have some conducting magnetic material under the antenna?
Is it to reduce multipath?

Best regards,
Adam

Adam,

Be aware that the signals from the Uputronics board (and similar) are most
likely to be at a 3.3V level, which /may/ not be sufficient to drive the DCD
pin on a traditional RS232 port, and you may need a level converter.  You
don't need to connect the other lines - send & receive - just the DCD and
ground.  I have a simple program which enables you to check for the pulsing
of the DCD line (and the other lines too):

https://www.satsignal.eu/software/net.htm#SerialPortLEDs

Yes, if you can use cgps or similar that would be fine - I just find the
phone handier!

The puck antennas are designed for use with a ground plane, and the maximum
pickup is then at 90 degrees to the ground-plane.  I don't think that on
these cheap antennas there's any multipath reduction, just more gain from
having the ground plane.  Be aware that in the new location the glass may
have some attenuation at 1.5 GHz as used by GPS.

Cheers,
David

SatSignal Software - Quality software for you
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv

On Sun, Aug 11, 2019 at 8:01 PM Achim Gratz Stromeko@nexgo.de wrote:

Thanks for all the info!
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.

I cannot see any difference between these positions. I've made 10
measurement for each position, getting 12 SNR values for satellites for
each measurement and then calculated the average of these.
Hanging antenna had 25.18 SNR average (2.21 standard deviation). Antenna on
a ground plane had 26.10 SNR average (2.08 standard deviation).
https://docs.google.com/spreadsheets/d/1lvGFTQS62MqiQALjHmWFZRY3hb5O1OqANFGBhnCaEUo/edit?usp=sharing

2 example screenshots from gpsmon included (before and after the change of
position)

If I take into account single high elevation satellite with good SNR
(satellite 26 in the examples), the new placement and ground plane even
lowered it :(
I guess the real benefit of the ground plane would be if the antenna was
outside, or my measurement method was wrong?

Best regards,
Adam

Adam Kumiszcza writes:

That way you changed three variables in one go.  You'd be better off
changing one single thing each time so you can see what changes cause
which results.  You do have a patch antenna (rectangular flat shape),
not a quadrifilar helix, do you?

Looking at your gpsmon pictures you seem to see the low elevation sats
at very similar SNR as (most) high elevation ones.  Any RF reflecting
things around in your neighbourhood?  Also, as David already mentioned,
thermo-pane windows are actually damping RF quite significantly and even
reflect them at low incidence angles.  You might try a few minutes with
an open window and otherwise unchanged antenna location to see what
happens.

The constellation providing your fix (four satellites minimum) should
probably all be well over 30dB, peaking in the mid 40dB SNR range.

You may have to experiment with antenna position a bit more.  I have
seen more than 15dB changes from rather small changes in antenna
placement.  It's definitely worth experimenting a bit to find one that
is good over the full cycle of the GPS constellation.

No, the ground plane (if your antenna needs one, not all do) is there to
improve the gain in the forward direction and make the elevation pattern
more uniform.  Outside oir inside doesn't matter, but antennas are
influenced by many things in their near-field region (at around 1.5GHz,
a few wavelengths at most, so ~30…50cm).  Again, you may be too close to
the window pane for instance.

Regards,
Achim.

+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf rackAttack:
http://Synth.Stromeko.net/Downloads.html#WaldorfSounds

On Mon, Aug 12, 2019 at 10:14 PM Achim Gratz Stromeko@nexgo.de wrote:

not a quadrifilar helix, do you?

It's a normal patch antenna, bought together with gps addon card:
https://store.uputronics.com/index.php?route=product/product&path=60_65&product_id=67

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.

On Mon, Aug 12, 2019 at 5:01 PM David J Taylor via time-nuts <
time-nuts@lists.febo.com> wrote:

be

unnecessarily!

I didn't have to stick to "good enough", David :)

Unfortunately, I will have to move this ntp server to another location (or
make another one and leave this one here). It will not have access to south
facing window there, only west is possible.

Best regards,
Adam