CDMA basestation transmissions must be synchronous with UTC to within 10 microseconds, typically much better - less than 1 microsecond.  This variation is due to the possibility that a basestation might have a GPS outage, a rare occurrence.  Under these conditions the basestation must stay within 10 microseconds of UTC for as long as 24 hours.  This ensures the smooth operation of the CDMA telecommunications system.

Our products are synchronous with the CDMA basestation transmissions from one to tens of microseconds, depending on location.  This variation depends on the propagation delay from our receiver to the basestation.  The propagation delay is about 5 microseconds per mile (about 3 microseconds per kilometer).  In an urban environment, there are many basestations and you would probably be within a mile of one.  Therefore the accuracy of the unit would be within 5 microseconds of the CDMA transmissions and typically within 6-7 microseconds of UTC.  Our main facility is located in an urban environment and our products test here to within 2 microseconds of UTC.  This is very typical for an urban environment.

In suburban or rural areas the basestations are spaced further apart.  This increases the propagation delay and therefore the accuracy of the unit degrades.  At our suburban test facility the units are synchronous with UTC to within 20-25 microseconds.  At our rural test facility the best-case accuracy we have seen is 30 microseconds and the worst-case is nearly 90 microseconds.  That would put the received basestation at nearly 18 miles away!

If you know approximately how far away the basestation is from your location you can eliminate this propagation delay component by using the CAL command via the serial I/O port.  Refer to the user's manual for more details.