[evlatests] Antenna 18 phase

[Rick Perley]

    A quick check to see if the EVLA phase-change-upon-frequency-change
has been repaired in antenna 18. 

    Continuum, changing frequencies amongst all bands round and round.
Three scans on X-band. 

    Antenna 18's phase seems to return properly.  The observed phase,
changed by ~+10 degrees between 1st and 2nd, and between
2nd and 3rd scans.  Could be a (large) baseline error, or perhaps expanding
fiber cables.  The time was early morning, the sky clear.    Antennas 13, 16
and 14 all showed large jumps of differing signs.