Jim, If I get you right, you want to compare the 10MHz outputs (not the 1PPS). As Jim and Bob told us so far, the thing is to provide, that input A _always_ starts before input B (or the other way around).
Connect the signals to an oscilloscope, and check, how much the phase differs - if the rising slopes occur close together, put some meters/yards of coaxial cable into one of the two signal paths. 1 meter is roughly worth 5ns - while the period of 10MHz is 100ns, 1m cable will phase shift about 18 degrees. I didn't verify, if the coax cable (with it's microphonic effect) affects the ADEV - does anybody have experience with this? Otherwise I'd have to fire up my counter and have a measurement on the run... Of course, inverting one signal will do as well. If you do it with extra electronics that definitely will affect the ADEV. I find it much easier to use some meters of cable. Ok, my counter is heating up by now... Volker Am 22.02.2014 14:17, schrieb Jimmy Burrell: > I need some help with a 'noob' question regarding some practical examples in > some of the NIST literature. When attempting to compare two clocks, I'm a bit > confused on the subject of exactly how to use my counter to compare a delayed > clock relative to another. Or perhaps I should just say 'comparing two > clocks'. Let's take some concrete examples. > > Let's say I want to characterize my Morion MV89 ocxo using my HP5335a. > Obviously, I can tune the MV89's 10MHz by +/- 1Hz and feed it to the > counter's input 'A'. Obviously, I can feed in a second, external reference > clock at 10MHz into input 'B'. Suppose, however, I didn't have an external > reference clock. Can I compare against the counter's internal time base by > hooking a line from the rear jack time base output to channel 'B' input? Or > am I making it too complicated? Do I simply plug into input 'A' and go? > > In a somewhat related question, in this article > (http://www.wriley.com/Examples%20of%201%20PPS%20Clock%20Measuring%20Systems.pdf) > where two clocks, both divided to 1PPS, were compared, W.Riley makes the > following statement, "The two 1 PPS outputs were connected to a Racal Dana > 1992 time internal counter having 1 nanosecond resolution, and the start and > stop signals were separated sufficiently in time for the counter to function > properly". I wonder what exactly is meant by "separated sufficiently in time > for the counter to function properly" and how one would go about doing this? > For example, is inverting one of the signals sufficient separation? If not, > how is this typically done? Delay line? > > Thank you, > > Jim... > N5SPE > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
