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

[Rick Perley]

     I'm reducing science data taken on the strong quasar 3C273. The 
program cycles through X, Ku, K, and Ka bands.

     Overall, data quality is excellent.

     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).

     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.

     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.

     These jumps are definitely *not* due to atmospheric effects -- 
which are easily seen on all antennas, are of a completely different 
characteristic.

     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.