[time-nuts] Why are 1PPS signals so skinny?

Magnus Danielson magnus at rubidium.dyndns.org
Mon May 14 19:20:12 UTC 2012


Mark, Azelio and Björn,

On 05/14/2012 06:33 PM, bg at lysator.liu.se wrote:
> Mark&  Azelio,
>
> Or even 10V into 50ohm, 20us... See figure 3-4 in ICD-GPS-060.
>
>      http://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf
>
> More modern 3-5.5V into 50ohm, 20us.
>           http://contracting.tacom.army.mil/majorsys/jab/DAGR%20Interface%20Specification.pdf
>
> Above are two standards demanding short skinny 1PPS pulses. Are there any
> other standards with distinct shape requirements on 1PPS pulses?

You need to look at MIL STD 188/155 which if I recall things was 
initially formed in the 60thies.

An AccuBeat presentation actually says that the PPS was originally 
defined in it.

The MIL STD 188/155 is actually a 10 V peak level, so it was much hotter 
than we are used to know. It specified 5 MHz as base frequency, or power 
of 2 multiples (10, 20, 40 MHz... ).

It was later reformulated in the PTTI spec, which ICD GPS 060 is a 
derivate. The 50 ns rise and 1 us fall slopes comes from that spec.

I was not able to find MIL STD 188-155 on the net right now, but I have 
been able to download it before, so if someone is a more lucky it should 
surface. I should have my download somewhere.

Cheers,
Magnus




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