[time-nuts] Measuring 1 PPS with an HP 5335A

Bob Camp lists at rtty.us
Sun Feb 16 14:33:01 EST 2014


On all these counters, you need to switch to DC input for 1 pps signals. You also need to manualy set the trigger level to something like +1.5V. Next thing to fiddle is the 1 meg / 50 ohm termination. Sometimes it works better with 50 ohms, sometimes not.


On Feb 16, 2014, at 2:03 PM, Jimmy Burrell <jimmydburr at gmail.com> wrote:

> I've recently purchased an HP 5335A and for the most part, we're getting along famously. Then I tried to measure my GPS' 1 PPS pulse. I'm not seeing anything Iike what I'd expect to see, e.g. 0.000001. Doesn't matter what type of measurement I select (freq, period) the measurements are nowhere near "1". In fact they are all over the place and changing a lot faster than once per second.
> My first thought was "not enough signal" present at the input of the counter causing a low SNR. But my scope says it's better than 2v on p-p. According to the HP5335A manual, that should make the counter happy.
> I've never tried measuring any freq. this slow so I'm out of my element. Probably missing something obvious.
> Any of this ringing a bell with anyone? Any clues or suggestions?
> Many thanks,
> Jimmy...
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