[time-nuts] FE-5680A performance

[Chris Albertson]

I found the undocumented PPS signal on pin 6.   This is on the "new" $38
unit I just got.

Question:  Can anyone measure the pulse?  How wide is it and what is the
voltage?

Here is my setup:
Have an older Tek 465 scope that is in only "fair" shape and I see nothing
on that pin but milivolt level sine wave of about 60MHz.  I can't set the
scope to show any hint of a PPS but I know it's there because I routed the
scope's vertical amplifier output to channel A of an HP5328 counter,
measured period A and I get 999997.5 uSec period.  So I'm sure the PPS is
going through the scope.  But I can't see it so I can't measure it.

Next I place the PPS from an Oncore UT+ GPS on Channel A and I get very
close to the same period.  I suspect my counter needs calibration.

Next experiment:  Route the FE-5680's 10MHz output to the counter's
external clock input.  Now the counter is running off the Rb.  Then I
measure the GPS' PPS and the period is exactly 1 second except for the last
digit which some times flips to 1 or 9 (the expected one count random
error)   So I think the Rb is better than whatever oscillator is inside the
HP counter.

Next experiments are a long term comparison of the GPS and Rb PPS but I
need to know the height and width of the FE5680's PPS.

I
Chris Albertson
Redondo Beach, California