"David Woolley" <[email protected]> skrev i meddelelsen news:[email protected]... > Towli wrote: > >> >> I am really trying to understand this, and i feel a little >> stupid, -perhaps i dont get it because english is not my native language: >> Why is my 3750 switch reporting a precison of 2**-6 when using my >> appliance DCF77 box, but reporting precison of 2**-18 when talking about >> the external Gps-servers. > > Because the DCF77 box can only read its software clock to the nearest 10 > to 20ms, whereas the external GPS server is presumably running on a recent > Unix or Linux system and can interpolate its software clock reading to > better than the nearest 5 micro-seconds. > > I don't remember your providing any output that would indicate the > precision reported by the router, but it may well be at the poor end. > >> If i erase the ntp clock-period from my switches when they are in synch >> with my appliance box - would the precision improve ? > > > The only way of improving it is to use a better radio clock box. It will > be fundamental to the software on that box, which might also be > constrained by the hardware, if it has no means of reading the residual > timer count, or otherwise interpolating. > > I'm not sure that precision is a problem here. The basic problem is that > you have a fast connection to GPS clocks and GPS has an intrinsic error of > about 50 nano-seconds, and a good GPS based time server can achieve about > 1 microsecond, with no time of flight considerations, whereas as a slow > code DCF77 receiver may have difficulty getting the time to better than a > few milliseconds, and will require correcting for the radio propagation > delay if you want high accuracy.
There you go...Or there i go...Now i get it! Thank you so much ! ! ! Im getting shivers down my spine, because of people like you guys in here who are prepared to help out newbies like myself, without anything but appreciation in return. Thank you ! /Towli _______________________________________________ questions mailing list [email protected] https://lists.ntp.org/mailman/listinfo/questions
