[time-nuts] Why/when did cell towers switch to 15 MHz?

[Mike S]

At 04:51 PM 11/16/2008, Hal Murray wrote...
>So why did cell phone towers switch to 15 MHz?  Or is it just Lucent 
>that switched?

Ultimately, CDMA base stations need a precise 1.2288 MHz clock, as that 
is the chip clock rate. A PLL locked to a 10 MHz GPSDO (like the 
Tribles and HP Z3801s, which came out of Nortel BSC/BTS CDMA base 
stations and were known as GPSRs) were probably used originally simply 
because of easy commercial availability.

Some newer units (Nortel GPSTM, used in their newer Metrocell base 
stations) output 9.8304 MHz, which is an 8X multiple of the chip rate. 
These also put out 10 MHz and 0.5 Hz (even-second) signals.

Did Lucent switch, or have they always locked to a 15 MHz source? I've 
only seen the 15 MHz units.

Any Timenuts have an Endrun Tycho CDMA-derived frequency reference? 
http://www.endruntechnologies.com/pdf/TychoCDMA.pdf
http://www.endruntechnologies.com/pdf/PTTI2001_WhitePaper.pdf