[time-nuts] Ublox neo-7M GPS

Said Jackson saidjack at aol.com
Tue Aug 19 17:46:24 EDT 2014


Tom,

Btw part of my frustration with this is that we sometimes get calls from customers asking why they need our or others' GPSDOs for a couple 100 dollars when they can buy a CW or uBlox doing "the same thing" for a fraction of the cost.

Most of them come back to us after evaluating these NCOs and finding that its not the same thing.

You get what you pay for I guess..

Said

Sent From iPhone

> On Aug 19, 2014, at 13:01, "Tom Van Baak (lab)" <tvb at leapsecond.com> wrote:
> 
> Hal, as long as you maintain long-term phase lock it's a disciplined oscillator. So, yes, a carrier tracking WWVB receiver with sufficiently stable flywheel LO is a WWVBDO.
> 
> Said, too-short or too-long 100 ns cycles is one thing. Still ok for many applications. But tell me more about extra or missing pulses in the ublox-7. That sounds like a show stopper to me.
> 
> /tvb (i5s)
> 
>> On Aug 19, 2014, at 2:05 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
>> 
>> 
>> SAIDJACK at aol.com said:
>>> its not a GPSDO though, not even a simple one :)
>>> It does not discipline an oscillator. It generates the output by
>>> mathematically calculating how many phases it has to add/drop in a second,
>>> then   digitally adds/drops/extends/retards the phase of the output clock to
>>> achieve an average of number of desired clock cycles.
>> 
>> Is there something about the term GPSDO that says I have to do the "D" in the 
>> analog domain rather than the digital domain?
>> 
>> I agree that current technology doesn't give results that are useful for many 
>> applications that currently use GPSDOs.  What if the clock ran at a GHz?  10 
>> GHz?  Sure, it would have spurs, but would it be useful for some applications?
>> 
>> Is a GPSDO still a GPSDO if the D/A driving the VCXO only has a few bits?  
>> How many bits does it need to be a real GPSDO?
>> 
>> Is a battery powered wall clock listening to WWVB at 2 AM a WWVDO?  It's got 
>> a pretty good ADEV if you go out far enough.
>> 
>> -- 
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list