[time-nuts] GPS and other low speed data via CAT5 wire

Hal Murray hmurray at megapathdsl.net
Thu Jul 3 02:32:43 EDT 2014


albertson.chris at gmail.com said:
> For GPS you need to also include the microseconds long pulse per second.  I
> think it might by the very short duty cycle of the pulse that makes it hard
> to transmit using RS-232 style signaling.

The problem with short PPS pulses is that some PCs don't catch them.  (I have 
one that only catches some of them.)  One simple solution is the FatPPS from 
TAPR.
  https://www.tapr.org/kits_fatpps.html

Many (most?) low cost GPS units with a PPS have a long one, 100 ms or 500 ms. 
 I think the Garmin GPS-18 units are adjustable in 100 ms steps.

Most of the GPSDOs have short PPS pulses, typically 10 or 20 microseconds.
  The HP Z3801A manual says 10-50 microseconds.  My scope shows about 26.
  I couldn't find any spec in the TBolt manuals.  My scope shows 10 
microseconds.


-- 
These are my opinions.  I hate spam.






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