[time-nuts] FE-5680A performance - 1 PPS output issue

[beale]

I think there is something funny about the 1 PPS output on pin 6 from the currently available cheap FE-5680A units. I have three of these units. On one unit, on one occasion, I did observe a logic-level 1 PPS pulse, exactly 1 microsecond wide.  But after a power cycle it never came back, although the unit indicates a locked condition, and is apparently working. The other two units also seem to work (10 MHz output OK, lock OK) but I have never seen a 1 PPS signal on pin 6 from them. My Tek TDS-210 is easily capable of triggering on and displaying a 1 usec pulse.  Is it possible the pulse appears only after a RS-232 command, or after some other special condition?


>  -------Original Message-------
>  From: David <davidwhess at gmail.com>
>  To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>  Subject: Re: [time-nuts] FE-5680A performance
>  Sent: 05 Jan '12 07:49
>  
>  On Thu, 05 Jan 2012 01:44:13 -0800, Hal Murray
>  <hmurray at megapathdsl.net> wrote:
>  
>  >albertson.chris at gmail.com said:
>  >>
>  >> 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 ...
>  >
>  >I do have a 465.  You should be able to see a 1 uSec PPS.
>  
>  60MHz is about a 6nS rise time and is easily fast enough to see it.
>  
>  >Now turn up the Intensity until you can see the pulse.  It might help to turn
>  >down the room lights.
>  
>  This is the problem.  With a 1 second repetition rate, the brightness
>  is going to be very low.
>  
>  The old ways of viewing such a low repetition rate signal include
>  using a hood or dark room, special CRT phosphors, photographic film,
>  MCP (micro channel plate) intensified CRTs, and of course analog
>  storage and later digital storage.
>  
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