I clearly need three of those maser things for my network.
Gives new meaning to the phrase "Set and forget". :) -mel beckman
On May 14, 2016, at 12:40 PM, Baldur Norddahl <baldur.norddahl@gmail.com> wrote:
On 13 May 2016 at 23:01, Baldur Norddahl <baldur.norddahl@gmail.com> wrote:
Ok how many hours or days of holdover can you expect from quartz, temperature compensated quartz or Rubidium? Should we calculate holdover as time until drift is more than 1 millisecond, 10 ms or more for NTP applications?
I am thinking that many available datacenter locations will have poor GPS signal so we can expect signal loss to be common. Some weather patterns might even cause extended GPS signal loss.
I found some data points here: https://en.wikipedia.org/wiki/Crystal_oven
Assuming that acceptable drift is 10 milliseconds due that being the expected accuracy from NTP.
The common crystal oscillator can be as bad as 1E-4 => holdover time is 2 minutes. TCXO is listed as 1E-6 => holdover time is 3 hours. OCXO is listed as multiple values, I will use 1E-7 => holdover time is 1 day. Rubidium is listed as 1E-9 => 3 months Caesium is listed as 1E-11 => 30 years Hydrogen Maser 1E-15 => 300 millennia
I clearly need three of those maser things for my network.
Regards,
Baldur