[daip] regarding frequency increments in AIPS

[Eric Greisen]

Neeraj Gupta writes:
 > Dear Eric,
 > 
 >       Greetings from Sydney.  Dave Green and I have a couple of queries 
 > regarding the way IFs with different frequency increments are handled by 
 > AIPS' tasks.
 > 
 > 1)  Do all the tasks (except for the ones like ISPEC which deal with files 
 > where there is no FQ table) in AIPS take the frequency increment and its 
 > sign from the FQ table?
 > 
 > 2) At one point (when I was communicating with you on a similar issue) you 
 > had said that DBCON, SPLIT and SPLAT in 31DEC06 have been fixed to handle 
 > the IFs with frequency increments having opposite signs.  Does this mean 
 > that there are still other tasks in AIPS which may not be able to 
 > deal with data files which have IFs with opposite signs?
 > 

It certainly is my intention that all tasks should read the FQ table
and manage opposite signed IFs appropriately.  There is no guarantee
that all tasks now do and I would not even know how to check
everything to be sure.  It is clear that the earlier autthors of these
tasks (me included) did not much worry abbout such things.  I do want
to suggest strongly that the more complicated the instrumental setup
the less likely all software will correctly support it.  There were
reports a year ago of all sorts of bizarre troubles with GMRT data,
but they came at a time of much turmoil in my life and never were
properly addressed.  Since the complainers have not continued to ask
about things I have let that matter slide, assuming that work-arounds
and instrumental changes have resolved the problem.

Eric Greisen