locked Re: Clock Sync #Timesync


 

Jim,

I bought the VK-162 G-Mouse, and have it attached and running.  I have been using the procedure outlined below.  Perhaps I am misunderstanding something but here goes with what I am seeing:

I have 2 GPS pucks attached, both with different offsets.  My first trial I used the recommended 0.030 (30 milliseconds) and let everything run overnight.  This morning, the older puck was showing an offset of -236 and the VK-162 showed an offset of -69.  IAW your instructions, I reset the “fudge” offset to 296 and 99 respectfully.  Both pucks are attached via USB3 which probably won’t help jitter, but I would have thought the offset should not be that large. 

 

Given your better knowledge of this method of timekeeping do my numbers make sense to you?  Or am I just missing something?

 

__________

Dan – K4SHQ

CFI/II

 

From: main@WSJTX.groups.io <main@WSJTX.groups.io> On Behalf Of Jim Pennino via groups.io
Sent: Thursday, July 1, 2021 10:44 AM
To: main@WSJTX.groups.io
Subject: Re: [WSJTX] Clock Sync #Timesync

 

I haven't published the article yet as I am thinking of putting in some more things, like the difference between GNSS and GPS receivers and info on Linux, but here it is in its current state. Any suggestions from anyone how to improve the article would be appreciated.

I have been experimenting with GPS receivers and thought I would share
this for people wanting good system time, whether or not they have internet
access.

The VK-162 G-Mouse is a USB GPS puck available on Amazon from various
vendors for about $15.

This puck adheres to the standards for USB devices so is recognized by
native Windows 10 drivers and will keep the clock to about 1 millisecond
accuracy. I have no idea if older versions of Windows will support it.

Setup:

Plug the puck into the machine and after Windows tells you it is installed
and ready, run Device Manager and note the virtual COM port that has been
created.

Optional Testing:

Download and install VisualGPSView from https://www.visualgps.net.

This is a free utility to view GPS output and it can check that your GPS
is working and sees satellites.

Run the program, click on Tools, then on Connect GPS. Enter the COM
port you got from Device Manager and 9600 baud.

Within a few seconds you should get a display of satellites seen and
their status. There should be more than 10 satellites seen. Try moving
the puck around or putting it on a window sill to get the most satellites.

If no satellites at all, double check the COM port and baud rate, or be
ready to tell Amazon it is DOA and send a new one. I have 6 and no duds
so far.

Kill VisualGPSView. Both VisualGPSView and ntp want exclusive access so
both can not be run at the same time.

Install and Configure NTP:

Download and install/upgrade the latest ntp from
https://www.meinbergglobal.com/english/sw/ntp.htm

When you configure ntp you can use the ntp pool or other ntp servers if
you wish, but the GPS receiver is likely to be far better than any
remote server so other ntp servers is like belts and suspenders when
you have a REALLY good belt.

Add the following two lines to ntp.conf:

server 127.127.20.n minpoll 4
fudge 127.127.20.n time1 0.030

Where 127.127.20 says this is an attached clock on COM port n.

Replace the n with your COM port shown by Device Manager.

The 0.030 is the typical calibrate constant for hardware delays.

Start ntp and run the Quick NTP Status program.

You should see a status window that updates every 10 seconds.

After ntp has been running for some minutes, the 127.127.20.n line
should have a '*' in front of it indicating it is using the GPS for
time and the reach value should become 377, meaning no problems talking
to the GPS.

Offset Calibration:

After ntp has been running for at least an hour, check the status and
note the offset number. If it is less than 10, the 0.030 previously
entered is close enough.

If the offset is greater than 10, round it to the nearest integer and
divide it by 1000.

Edit ntp.conf and subtract that number from 0.030 and enter the new
number. Pay attention to the sign as if the offset number is negative,
you must add that amount to 0.030.

Restart ntp and after a while the offset should be less than 10.

Note: Depending on how you install ntp, some of the Meinberg programs
may require Administrator privilege to run.

Join main@WSJTX.groups.io to automatically receive all group messages.