[ntp:questions] Re: Which PBS station should I use for the time signal?

Mark Crispin mrc at CAC.Washington.EDU
Wed Nov 16 17:00:13 UTC 2005

I think that it is a false presumption that the time signal sent by PBS is 
accurate.  As far as I can tell, it is set from some operator's watch and 
*not* from an accurate timebase such as GPS or WWV.

In the Seattle area, PBS sets the time at least a minute fast, compared to 
time from GPS.

For what it's worth, the time that DirecTV sends to its receivers is 
pretty good, although I haven't checked it against GPS time.  You may have 
to hunt in the menus to find the time reported to 1 second resolution 
since usually it just shows hh:mm

Most CDMA cell phone networks (Verizon, Sprint, etc.) transmit GPS time. 
CDMA requires a precise timebase across the entire network and usually (I 
have seen exceptions with isolated rural networks) they synchronize it 
with good time.  That is not the case for GSM or TDMA cell phone networks, 
which are generally set from an operator's watch.

-- Mark --

Democracy is two wolves and a sheep deciding what to eat for lunch.
Liberty is a well-armed sheep contesting the vote.

More information about the questions mailing list