[time-nuts] I've designed a GPSDO, but how "good" is it?
nsayer at kfu.com
Sun Aug 16 15:39:19 EDT 2015
> On Aug 16, 2015, at 12:31 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
> Anyway, to answer your question -- to measure its true performance you only need two things. 1) a phase meter (or time interval counter) that's good to 1 ns or better, and 2) a local reference standard that's maybe 10x better than the TCXO and the Adafruit GPS. Usually that means a cesium standard, or supremely qualified GPSDO, or equivalent.
I have a frequency counter, but it’s not a phase meter. I have a scope, but I assume that trying to use a ruler with scope traces isn’t the textbook way of doing that. :D
I have considered in the past buying a used rubidium standard off eBay, but have hesitated because I don’t know how much life there is left in the tube, and I just have to take it on faith that it’s stable and accurate. I have somewhat more faith in the GPS PPS, but clearly that has limits.
> A number of us here on the time-nuts list have such equipment at home. And unlike professional labs, we will do it for free/fun if you loan the GPSDO for a week.
I will happily *give* one to someone if they would be willing to help a relative newbie with this stuff.
Just one though. They’re kind of expensive to build. :D
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