[evlatests] BD T304 power meters and attenuators

[Ken Sowinski]

Rob has told me that power meters are now available in all T304s.
This raises the question of what to make the default attenuator
setting algorithm for IFs B and D.  I would like to make the
ALC at scan change the default and no longer maintain the BD
attenuator settings in parminator.

Some considerations.

OPT generated script would have to set the BD T304s to use
set-and-remember whenever it does so for AC.

Both IF pairs will now be reasonably set regardless of tuning
within a band.

We will have to use this, probably without set-and-remember,
for the three bit samplers.

Use of ALC modes will force us to understand how the attenuators
modify bandpasses.  If set-and-rememeber is used too avoid
attenuator changes, the details when multiple tunings within a band
are used can be messy.

When eight bit samplers are used it can be argues that the best
approach might be to set all the attenuators from a table of
values.  There might be some merit to this at L band where
interfence can make ALC operation unreliable.


I argue we make ALC the default and allow the ovserver to choose
different strategies in the OPT based on the particular scenario
for that observation.  Someone will have to invent a few probable
and useful scenarios.