[ntp:questions] Confused about pool rotation

Mike S mikes at flatsurface.com
Thu Feb 7 12:35:55 UTC 2013


On 2/7/2013 2:17 AM, Terje Mathisen wrote:

> Most (GSM/3G/4G) cell towers make do with OCXOs/TCXOs, but very good
> ones, rated at a few ppb/day in drift rate.
  ...
> The interesting part here is that the actual requirement is for
> _frequency_ synchronization, not absolute time sync!

You're probably not familiar with CDMA systems, which absolutely MUST be 
synchronized in both time and frequency.

http://www.cdg.org/technology/cdma_technology/a_ross/systemtime.asp

Hence the appearance of surplus GPSDOs, like the HP Z3801A, which was 
part of a Nortel CDMA BTS.





More information about the questions mailing list