[evlatests] Maser Tomorrow

[Vivek Dhawan]

Hi Keith,

todays' short test shows the following:

      Rb, at 01 UT MJD 56420 = 7pm May 7th:

 From VLBI (vs. MK)         +115 usec, rate +5.2e-10 s/s = 45 us/day.
 From L356 clock #1 vs.gps:  +88 usec, rate +5.2e-10 s/s

The rate is right on the money. The offset is a little off, but it
is in the realm of what we got on 'good' days (i.e. within ~20usec).
This was a 1MHz narrow band experiment, and we know there is a BW-
dependent delay offset which might be VLA or more likely VLBA filter
delays. So I am in a state of tentative belief in the L356 monitor.



      H maser, at 01 UT MJD 56420 = 7pm May 7th:

 From L356 clock 1 vs.gps:  offset (+1s - 0.7us), just under 1 sec.
                                                    rate near zero.

Is the ~1sec understood? Will it be removed before synch?. If so
I think the H-maser can go in tomorrow.




Keith Morris wrote:
> We have been monitoring and adjusting the drift rate of the Maser since 
> it was installed at the VLA site two weeks ago.  A frequency adjustment 
> was made yesterday morning, and the drift rate since then is 
> unmeasurable at the resolution of this monitor point, which means less 
> than 8ns/day.  More importantly, the rate appears to be stable.  I 
> recommend that we switch the system back to Maser during tomorrow's 
> maintenance day.
> 
> This means that we will need to resynchronize, since the difference 
> between the maser offset to GPS and the rubidium offset to GPS will 
> likely be greater than the sync detect window in the L350.  Presently, 
> the Rubidium offset to GPS is around 76us (leading), and the drift is 
> accelerating.
> 
> If anyone objects to this, please let me know.  Otherwise we will 
> proceed tomorrow.  If it is decided that we should *not* make the 
> switch, then I would recommend that we make another frequency adjustment 
> to the Rubidium.  I am coordinating with Kerry to avoid conflicts with 
> the correlator testing.
> 
>