[ntp:questions] GPS_NEMA, but high offset and jitter?

David Lord snews at lordynet.org
Fri Feb 26 09:49:01 UTC 2010

David J Taylor wrote:
>> Is there any other way to watch the signal to see if it's reaching the 
>> serial port correctly?
> I would use my 'scope, but even an analogue voltmeter might work - see a 
> regular flick of the needle.  I built the equivalent of a simple 
> break-out box into my two connections, one in the RS232 DB-9 plug itself:

I checked pps from MSF rx with digital meter and that showed a
signal but not very well. That has a 50ms pulse so 100ms from
Garmin should be as easy to spot. Analogue meters I have around
would give a much better indication.

Another alternative is a transistor + three resistors and
LED. A pot could be used for R2 to confirm voltage swing
of PPS output.

     +5V -- R3 --- LED ---+
     pps --- R1 ---+--- b
                   |      e
                   R2     |
                   |      |
      0V ----------+------+


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