Hi Said,
On 3/30/2012 10:53 AM, Said Jackson wrote:
Hello Ed, Azelio,
We should also compare the same parameters. Sawtooth error of the m12+ of
+/-25ns is not its standard deviation, it's max/min. Compare that number to
your 30ns max/min measurement on the 5372a.
Yes, you're right. Thanks for the clarification.
Standard deviation of the m12+ is around 2ns with correction. That needs to be
compared to the 5ns you measure on the 5372a as that is the best performance
you will get from the CW12. Yes the uncorrected 1pps of the m12 is worse, but
it is designed to be used with correction. So in the end the m12m still
performs better than the CW12.
That's why I suggested to the OP that if the Commsync II uses sawtooth
correction the CW12 might not improve his performance. The limited
command set you mentioned in your other message is another potential
problem.
Ed
Bye,
Said
Sent From iPhone
On Mar 29, 2012, at 1:56, Azelio Boriani<[email protected]> wrote:
We (that is my company) use the CW12-TIM (NMEA version) and its PPS wonders
as usual, nothing different from a uBlox LEA-5T or the M12M.
On Thu, Mar 29, 2012 at 9:32 AM, Hal Murray<[email protected]> wrote:
The sawtooth error on the Motorola M12+ is about +/- 25ns, while the CW12-TIM
has a sawtooth error of +/- 2 ns, so correcting for the sawtooth error is not
as critical with the CW12-TIM.
The first claim
The sawtooth error on the Motorola M12+ is about +/- 25ns
is correct but are you absolutely sure that the second claim is correct too?????
It would mean a factor>10 improvement of the CW12-TIM against the M12 which is
hardly believeable.
The 25 ns probably comes from period of the the free running clock they are
using. It doesn't seem unreasonable to me to get 10x better if they use a
GPSDO for the local clock so they can get the PPS edge right where they want it.
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