[evlatests] ea28 pointing problems

[Ken Sowinski]

There were two problems.  The azimuth pointing variation with
elevation was caused by the "loose bottom maypole".  This has
been repiared and verified.  The second problem is likely a
"bump" in the azimuth bearing.  A careful comparison of the
post-fit pointing residuals with the level measurements done
by Jon, Lew and Bob shows good agreement with a roughly half
arc-minute elevation bump over the range of about 270 to 360
degrees of geographical azimuth.

The antenna may be moved whenever convenient.  It is still
among the worst pointers, but no longer stands out as the
very worst.

Six evla antennas have had bearing replacements: ea14, ea16
and ea28 are point poorly because of unmodeled bumps.  ea18
and ea26 are both point very well in the sense that the
unmodeled arrors are very small.  Perhaps we need to consider
a bearing analog to the VLBA track model to account for
bearing/track imperfections.