[time-nuts] NTP server using an OCXO, GPS chip and Raspberry Pi

[Petr Titěra]

On 25.04.2020 12:19, Hal Murray wrote:
> 
> David Taylor said:
>> With those recommendations, and noting the delays in RPi I/O (at least in
>> the earlier RPi cards where Ethernet is over USB), I would suggest that an
>> OCXO is overkill.  No reason to deviate from the Raspbian OS.
> 
> That's an important point.  Thanks David.  I'm embarrassed that I didn't
> mention it.
> 
> On Pi 2 and Pi 3, the Ethernet is on USB which adds a layer of jitter to the
> timing you can get using NTP.
> 
> 
What is considered as too much jitter in this case? I see this in my 
home setup:

      remote           refid      st t when poll reach   delay   offset 
  jitter
===============================================================================
  SHM(0)          .SHM.            0 l   34   64  377   0.0000 -57.9552 
  1.6973
*SHM(1)          .GPSD.           0 l   13   16  377   0.0000  -0.0016 
0.0004
+192.168.3.246   .PPS.            1 u   17   64  377   0.3834  -0.0064 
0.0149
-192.168.3.247   .PPS.            1 u   18   64  377   0.3545  -0.1689 
0.0069
+192.168.3.102   .PPS.            1 u   15   64  377   0.1966  -0.0729 
0.0187


Server 192.168.3.246 is RPi3.

Petr Titera