In a message dated 4/28/2007 22:21:55 Pacific Daylight Time, [EMAIL PROTECTED] writes:
>Obtaining 100ps resolution, particularly when one is only making 1 >measurement per second, is relatively easy and inexpensive to do with a >few discrete components. >Obtaining much better than 150ps resolution is somewhat more difficult >when using the technique employed by the HP53131/2 in its CMOS gate array. >Bruce Hi Bruce, that may be, but I don't believe the Z3801A has 100ps hardware resolution until someone proves it to me. Maybe we should ask Jack Kusters, he worked on that unit. I just don't think that HP would have given the Z3801A 100ps resolution, and the 53132A "only" 150ps resolution. Doesn't make any sense, since the counter absolutely needs the resolution, but a GPSDO does not. Quite frankly there is no need for that kind of resolution since the noise on the VP Oncore is 104ns peak to peak. Why would you have 100ps per second resolution if that is three orders of magnitude below your inherent 1 second noise?? Another fact is that the GPSDO will average that resolution over say 1000 seconds anyway in it's control loop, so 100ps average over 1000s is orders of magnitude better than any OCXO local oscillator could achieve anyway. Also, what is the granularity of the VP Oncore 1PPS output? I am sure that it's orders of magnitude above 0.1ns, so even if the Z3801A TI hardware had that kind of resolution, it would be way more than needed. They probably have 1ns - 5ns hardware resolution, and simply average down to 0.1ns apparent resolution. I hope someone familiar with the Z3801A hardware here can shed some light on this :) bye, Said ************************************** See what's free at http://www.aol.com. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts