[ntp:questions] wwv performance on debian etch

David L. Mills mills at udel.edu
Mon Nov 26 22:03:45 UTC 2007


David,

Your first two servers are in the mix with the WWV driver and could be 
causing some offset. To avoid this, put noselect options for all servers 
except WWV for test. When signals are good, I generally get within 0.1 
ms in both offset and jitter with respect to a PPS from GPS.

To get to this degree, you need accurate propagation delay to well 
within 1 ms. Note that, as it says in the driver HTML page, this is good 
enough to follow the ionosphere wanders up durint the day and down at 
night over a range of about 1 ms. This is for a two-hop F2-layer path, 
which is common here on the right coast. If you are in E-layer range, 
the difference can be more dramatic.

Dave

david.margrave at gmail.com wrote:
> I have a ramsey wwv receiver with the mod suggested by steven bjork
> (resistor +capacitor between pins 1 & 12 of the LM389).    My hardware
> is an Asus pundit system whose primary purpose is a PVR (myth TV).
> 2.6.18 kernel.
> 
> I've got a good strong signal (40 dB if I'm reading it right)
> 
> 54430 55860.013 127.127.36.0  0 2007 330 15:31:00  S -2 0 127 WV15 82
> 0 127.1 51
> 2
> 54430 55862.013 127.127.36.0 wwv5 001f 251 2517 3037/24.4 4463/18.1
> WV15 ffbf 99
>  5604/40.0 WH15 0000 0 8/-22.2
> 
> Is this good offset & jitter?  I also have 4random servers from
> pool.ntp.org:
> 
>      remote           refid      st t when poll reach   delay
> offset  jitter
> ==============================================================================
> +clock.trit.net  192.12.19.20     2 u  128  512  377   37.035
> 2.014   0.308
> +hydrogen.cert.u 216.218.254.202  2 u   14  512  377   39.356
> 2.776   0.391
>  208-75-85-61.sl 82.211.81.145    3 u  626 1024    0    0.000
> 0.000   0.000
> -guinness.mcguyv 67.128.71.76     2 u  124  512  377   61.183
> -13.006   1.277
> *WWV_AUDIO(0)    .WV15.           0 l    2   64  377    0.000
> 1.081   0.064
> 
> neat stuff.
> 
> Dave
> 
> 
> 




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