[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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