[time-nuts] 1PPS for the beginner

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 18 03:32:28 EDT 2018


Hi,

On 08/15/2018 06:03 AM, Björn wrote:
> Hi Bernd,
> 
> One reference to 20us 1PPS pulse length is the ICD-GPS-060, see figure 3-2, page 3-3 (pdf page 19)
> 
> https://www.navcen.uscg.gov/pdf/gps/ICD-GPS-060B.pdf

However, very few boxes does deliver 10 V amplitude PPS pulses. They may
be 20 us, but then as "TTL levels into 50 Ohm" meaning a peak of about
2,5 V as result of 50 Ohm source impedance and 50 Ohm load impedance
voltage dividing the driving 5 V.

The MIL-STD-188-115 also has the same specification on page 12.

There are a few more in that cluster. I have not bothered to pull them
all down. It relates to the PTTI Interface so I expect them to be similar.

> Group - Are there other standard documents defining duty-cycle, voltage levels, rise times etc?

I think ITU managed to put one in their standards (finally), I'll check
for it.

Cheers,
Magnus

> MfG
> 
>      Björn 
> 
>> On 14 Aug 2018, at 20:52, Bernd Neubig <BNeubig at t-online.de> wrote:
>>
>> Another question, a bit off the road of this thread: 
>> Is there any common practice for the duty cycle of the 1 PPS pulse?
>> I have seen devices having extremely short 1 PPS pulses with duty cycles of a few percent or less and others with close to 50% duty cycle.
>>
>> Best regards
>> Bernd
>> DK1AG
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