[time-nuts] What is the best counter for a Time Nuts?

[Mike Monett]

  "Tom Van Baak" <tvb at LeapSecond.com> wrote:

  >> 24 hrs  would get you to 2.77e-10 / (24 * 3600) =  3.2e-15, which
  >> is very acceptable. That puts you in the big leagues.

  >Hi Mike,

  > It doesn't  quite work this way. If it did, hey, you could  wait a
  > month, and be better than the big leagues!

  > The missing consideration is the stability of the test  setup. The
  > frequency reference  and the phase comparator would  have  to have
  > 10^-15 levels  of  stability before you could claim  this  sort of
  > per-day measurement resolution. I can tell you a  telecom rubidium
  > and hp3575A are not even close to this.

  I know. All I was saying is he could resolve a  frequency difference
  of 3.2e-15 in 24 hours. That is big league stuff.

  As you  point  out, that is far better than  the  oscillators  he is
  using. So  his  method  is valid, and his  equipment  is  capable of
  making useful  and important measurements. Since it is  a completely
  different method, it would give a valuable cross-check against other
  methods.

  As far as the measurement stability, the phase measurement is merely
  measuring the  time between two signals. I would expect  HP  to hold
  much better than 0.1 degree with no problems. Since it  is measuring
  a relatively small change and not an absolute value,  the resolution
  of 0.1 degree could be considered valid data.

  So his equipment is capable of resolving a frequency difference that
  is much smaller than the stability of the oscillators. That is good.

  But we don't know what would happen during a 24 hour run. So  what I
  was hoping for was a table of phase angle measurements perhaps every
  15 minutes for the first several hours to get a feeling for  the ups
  and downs  of the phase angle drift, then perhaps every  hour  for a
  couple of days. That would be very valuable data.

  >> Can you see any drift in the GPS time?

  > You're not  likely  to see "drift in GPS time" when  using  a free
  > running rubidium or another GPSDO as a reference. Do you see why?

  Sorry, badly  worded. I thought he locked the rubidium  to  gps, and
  was wondering  if he monitored the DC error to the rubidium,  and if
  he saw any diurnal change.

  If so, that would indicate the rubidium is quite stable by itself.

  >/tvb

  Best Regards,

  Mike Monett