[time-nuts] 1PPS for the beginner

Bob kb8tq kb8tq at n1k.org
Tue Aug 14 11:05:17 EDT 2018


Hi


> On Aug 14, 2018, at 10:33 AM, Ron Bean <time at rbean.users.panix.com> wrote:
> 
>> A normal GPS module generates it�\200\231s outputs off of a free 
>> running internal clock. Generally this is a TCXO in a 
>> �\200\234timing�\200\235 GPS ( = one that puts out a rational PPS).  
>> This i bit counter intuitive, since you would *think* they phase lock 
>> the local source in the module. They don�\200\231t mainly because it 
>> makes the math easier.
> 
> Is there a need to make the math easier?
> This is what we have microprocessors for.

There is *always* a need to make the math easier if I’m quickly typing up an example. For proof I
reference the hundreds of posts in the archives where I didn’t quite get it right :)

Indeed, the real numbers could be just about anything. They are highly dependent on what’s in 
the specific module. In some cases, the clock involved is well over 300 MHz. 

Bob

> 
> Thanks for the "hanging bridge" explanation. It would be nice if 
> someone had a time-nuts-glossary that included various terms that 
> come up on the list, like "hanging bridge", "spurs", "sawtooth 
> correction", "GPS allan ski jump", etc.
> 
> Is there a time-nuts FAQ?
> 
> 
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