[GPS_Standard] Problems PN2222A Inverter missing occasional 1PPS

[Bob Stewart]

Someone has just pointed out to me that a pair of 2N3904s will work in an non-inverting amp.  I've got a pair of 2N3646s, so that should do it.  And I think they're much faster to boot.

Bob





>________________________________
> From: Bob Stewart <bob at evoria.net>
>To: GPS Standard <gps_standard at mailman.qth.net> 
>Sent: Sunday, November 17, 2013 6:47 PM
>Subject: [GPS_Standard] Problems PN2222A Inverter missing occasional 1PPS
> 
>
>Michal and all,
>
>I'm still getting the occasional rare (maybe 5 or 10 a day?) glitch in my 1PPS pulse.  The symptom is a 2D00 instead of a 9680 in the oscillator count value.  This was puzzling until I realized that it's simply 2 times 0x9680, which means that from time to time I am not getting a 1PPS pulse.  As mentioned, the circuit is a simple inverting amp with 1800 ohms in the base lead to the 1PPS signal from the Adafruit, and 1800 ohms in the collector lead.  So, should I use a different transistor, or different values for the two resistors?  I want to keep this as simple as possible, so I would prefer not to have to add a chip, even if that would be the best solution.  I am not a hardware person, and just blindly designed the amp for low current.
>
>Bob - AE6RV
>
>
>