[evlatests] Phase/Delay jumps on ea13 and ea26 at X-band

[Rick Perley]

     Vivek owes me (most of) a bottle.

     He is correct that I did the wrong analysis:  I fitted the delays 
to the entire IF (eight spectral windows in this case), thus rubbing out 
most of the delay clunk effect, which works independently for each 
spectral window.

     When the delays/phases were correctly solved for, -- for each 
spectral window, and for each integration (1 second, in this case)-- , 
the *phase* steps claimed earlier are still there.  They are seen only 
in ea13 and ea26.

     Due to the wildly oscillating delay steps (more than 500 ps), it is 
difficult to discern if the claimed 40 ps steps are present.  I bet they 
are.

     Still to be done is to find if these steps are seen at other bands, 
and with the 3-bit samplers.

     Rick



On 04/12/2018 03:18 PM, Vivek Dhawan wrote:
> I bet this is delay clunks, seen through whatever processing
> was done by Rick. If I'm wrong, I'll treat him to a bottle of
> WalMart's (socorro) finest wine. and conversely...
>
> On Thu, April 12, 2018 09:50, Rick Perley wrote:
> |  Â Â Â  I'm reducing science data taken on the strong quasar 3C273. The
> | program cycles through X, Ku, K, and Ka bands.
> |
> |  Â Â Â  Overall, data quality is excellent.
> |
> |  Â Â Â  However, I've noted a peculiar effect for antennas 13 and 26, at
> | X-band (using 8-bit sampling).  There are two distinct delay/phase
> | states, differing by 40 ps in delay, and 140 degrees in phase.  (Likely,
> | the former causes the latter).
> |
> |  Â Â Â  In most cases, when the antenna is tuned to X-band, the resulting
> | delay can be 40 ps different than the last observation at that
> | frequency.  However, in many cases, the delay/phase jumps *in the middle
> | of the scan* to the alternate state.
> |
> |  Â Â Â  The jump scale is the same for both antennas, and is identical in
> | both polarizations.  The jump times, however, are completely
> | uncorrelated between the two antennas.
> |
> |  Â Â Â  These jumps are definitely *not* due to atmospheric effects --
> | which are easily seen on all antennas, are of a completely different
> | characteristic.
> |
> |  Â Â Â  I have yet to review the data from the other bands (or the 3-bit
> | data from X-band) -- and will report the results when I do this.
> |
> |
> | _______________________________________________
> | evlatests mailing list
> | evlatests at listmgr.nrao.edu
> | https://listmgr.nrao.edu/mailman/listinfo/evlatests
> |
>