[time-nuts] Cheap jitter measurements
Gary E. Miller
gem at rellim.com
Wed Apr 4 18:41:58 EDT 2018
TL:DR: I decided to go with the Rb and TAPR-TICC.
Thank you to all that made such good suggestions. I think you pretty
much covered the spectrum of options to measuring PPS very nicely.
I'm tempted by the used 5370/5371 idea. It has 150 ps resolution and
does a ton of fun things. But they are large, power hungry (500W), and
only talk over GPIB. I just want a TICC and the rest is overhead. All
the cool charts, graphs and histograms on the CRT do me no good.
Boxes like the Racal 1992 and hp 5334b are more interesting. Most
1991 on ebay are for parts only, and there are more web pages on how
to repair them than how to use them. They only resolve down to 1 nano
second. I do not see any of either on ebay with rs-232.
Since I'm just working with 5V and 3.3V logic levels, I don't need a
fancy front end, and output of logic level and/or USB serial is also
nice for using on a RasPi.
So I looked at the various hobbyist solutions. There are some
'interpolator' designs, but I'd need to build them myself and they also
only get to around 1 nano second. Some maybe a lot better performance,
but more than some assembly required. Also I would have to figure out
how to measure my measuring tool to see what I got.
So, I'm back to the Rb and TAPR-TICC solution. No one will seriously
question the Rb accuracy, at least when compared to GPS. The TAPR-TICC
comes fully assembled, tested and specified. Easy USB serial interface.
Just a tad more expensive than other solutions. 60 picosecond
resolution and less than 100 picosecond typical jitter. ADev below
1x10-10. All way better than I need, so few should argue with using it
to measure GPS PPS.
A few downsides. I'll have to write my own code for pretty graphs, but
at least I can do it on UNIX. Not a total solution, I still need to
add a GPSDO and cable it all together.
Now I just have to wait for the postman.
Once again, thanks for all the suggestions.
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
gem at rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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