[evlatests] Drops and jumps

[Rick Perley]

    I reviewed the fast-dump continuum data from late yesterday 
afternoon.  There are some important issues to address.  Here is a 
summary, sorted by antenna.  Most antennas behave well, but some don't.

Antenna 13

* Working well at L, C, X, K, and Q. 
* All phases are normal. 
* Very occasional single-record (0.418 second) amplitude drops on BD 
(both polarizations always together). 

Antenna 14

* All is fine at K and Q bands.
* IF 'C' is showing ~150 phase jumps ( back and forth) on timescale of a 
few seconds, at L and C bands.  (This is first time I've seen the phase 
jump like this at C band).  A single, short-duration jump in phase of 
this magnitude was seen at X-band. 
* IFs A and C gave no fringes at P band. 

Antenna 17

* Occasional short amplitude drops on BD at L, C, and K bands. 
* Otherwise perfect behavior. 

Antenna 18

* No problems of any sort and any band. 
* Clearly the poster-antenna for the EVLA.   We should talk about this 
one more  :)

Antenna 23

* Occasional short-amplitude  drops on AC. 
* Otherwise, perfect behavior on all bands (including P)

Antenna 24

* IF B is showing at least 4, and perhaps 6 'quantized' amplitude 
states, at all bands.  These levels are not uniformly spaced -- 
corresponding to power ratios of 1.6, 1.8, 2.4, ~6 for adjacent steps.  
There is no phase effect accompanying these multiple levels.
* A few short, amplitude drops were seen on the other IFs. 

Antenna 26

* A few small amplitude drops on AC at X and K bands.  (It has no 
receivers at C or Q).
* All four IFs have large steps in phase at X and K bands.  These steps 
are exactly coincident in size and time. 
* L-band was fine. 

Antenna