[time-nuts] Navsync CW12 - More Info

Ed Palmer ed_palmer at sasktel.net
Thu Jan 5 17:57:03 UTC 2012


Okay, I've cooled off - a bit.  The bottom line is that the 10 MHz 
output of the CW12 isn't appropriate for what I wanted to do.  Ah, the 
joys of reading and understanding a spec sheet!

But let's not throw out the baby with the bathwater.  Although the 10 
MHz output has it's issues for typical Time-Nut applications, the 1 PPS 
output is great.  Here are some measurements that I've made over the 
past few years on a few GPS receivers and a couple of GPSDOs.  I measure 
1000 periods of the 1 PPS and look at the results.  Every run gives 
somewhat different results so I've shown some typical ranges.  These 
measurements were made with an HP 5372A.  YMMV.

Device .............. Std Dev (ns).... Range (max-min)(ns) ... Device Type

Navsync CW12 ........ 4 - 5 .......... 20 - 25 ............... GPS Rcvr
Motorola UT+ ........ 40 - 55 ........ 95 - 110 .............. GPS Rcvr 
* see below
Rockwell Jupiter .... 10 ............  50 ...................  GPS Rcvr **
Motorola M12M ....... 10 - 15 ........ 40 - 60 ............... GPS Rcvr

Trimble Thunderbolt . 0.4 - 0.5 ...... 2 - 4 ................. GPSDO
HP Z3801A ........... 0.3 ............ 2 ..................... GPSDO    ***


*   Most of my UT+ 'range' results were in this group, but there were a 
few at 20 - 30.
**  Only one result.
*** Only one result.  I need to do more testing on the Z3801A


As you can see, the Navsync CW12 is by far the best of the GPS 
Receivers, but nowhere near as good as the GPSDOs.  However, imagine 
using the CW12 to discipline a good OCXO to build your own GPSDO.  Or 
using it to discipline a PRS10 Rubidium or X72 Rubidium oscillator.  You 
can't do it with the 10 MHz output, but the 1 PPS output is another story.

Ed







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