> As long at there is always a positive or always a negative time > difference between the two 1 pps signals the result makes perfect sense. > There appears to be about a 2 to 3 usec jitter in the 1pps from the > GPS (this is expected given the design of the receiver). > > If I put the 5370B in the +/-TI mode I expected to see both + and - > small time differences when the two signals are closely aligned - and > mainly I do. Typically the difference is + or - a usec or less. > Occasionally however the 5370B displays very near to a +1 or -1 second > (999.999 xxx ms or -1.000 000 xxx s for example) reading. Needless to > say this plays havoc with trying to measure a mean value of the > alignment. The 5370B is clearly measuring the "outside" between the > pulse pair when I want it measure the "inside" (or short time interval) > between the pulse pair. > > Is this normal behavior? Is there a setup that I am missing to make it > do what I want?
>From what I've seen it's best to stick with +TI mode for measurements like this. You don't want the counter making decisions about which half of the interval is "short" and which half is "long" -- it just doesn't add any value to the measurement. With 1-pps on both input jacks, your oscillator should remain within +/- 500 msec of GPS for a very long time, so you should be able to set up a combination of delays and/or edge polarities that will result in an arbitrarily-long set of phase measurements that never come anywhere near the 0 or 1000-msec points where the phase will wrap. (Even if they do wrap, it's not a big problem as long as you aren't using averaging on the counter.) -- john, KE5FX _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
