[daip] APCAL request.

[R. Craig Walker]

APCAL is far more robust than it was a few years ago and it has not given
me any trouble up to now in the M87 7mm project.  The defaults in VLBACALA
work fine.  But now I have a station that has Tsys's that are too bad for
it to get the receiver fit right.  I would like to get APCAL to do the
opacity fits in  the usual default manner for all other stations, but just
take a provided TRECVR for the offending station.  However as soon as I
try changing DOFIT and TRECVR for one station, all others change their
behavior entirely and don't seem to do the fit.  That is what the help
file claims will happen, but I don't see why.  In VLBI, the weather
conditions will usually be different at the different sites, so it seems
to me the program should allow the fitting to be station dependent.  Now,
I guess I'll have to try multiple runs of the program and of CLCAL.

Note that zero is not a reasonable first guess for TRECVR so you shouldn't
have to worry about distinguishing between that and a request for the
usual default behavior where it takes a guess.

When I tried multiple runs of APCAL, I tripped over another ambiguity. 
Inputs like DOFIT and TRECVR are keyed to some antenna index, but it is
not obvious which.  Well, it seems to be the number in the ANTENNA input
parameter, which was not my first guess.  I see in hindsight that the
behavior for DOFIT is specified in the help file, but it isn't for TRECVR.

Cheers,

Craig


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    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
    Phone  505 835 7247        P. O. Box O
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