[evlatests] problems related to 3-bit samplers

[Ken Sowinski]

ea26 now has a full complement of 3-bit samplers.  I have again
run simple scripts to verify that all the samplers are behaving
well in a general sense in preparatino for astronomical tests.

All the sample4rs in ea16, and ea23-D304 need attention and the
DTS group is investigating.

The ea13-l302-3, which is used for ea13-A2C@ consistently goes
to standby mode when commanded to 13073.1171.  It may do fso for
other frequencies as well, but I have not looked for that.
Commanding it elsewhere, and even rebooting the MIB, do not help.

Only one antenna, ea23  consistently failed to get the T304 attenuators
and equalixzers set correctly.  This was found to be because the
power feed to the downconverters was varying by a few dB on time scales
of minutes at C bnad.  At X band the power was stable.  When the antenna
is slewing the behavior is even more erratic: the power changes by a
few dB in seconds instead of minutes.