[daip] Possible problem with FRING

[Lincoln Greenhill]

Dear AIPS group:

Recently you fixed a problem with multi-band solutions by FRING
for irregularly spaced IFs.

This fix worked.  However, we see another peculiar behavior.

We are using 31DEC01 aips for this processing (on an alpha).
There is a subset of calibrator data available for anon-ftp at
rgalp7.harvard.edu   pub/nrao/BM112C-SCAN.FITAB .

Symptom: Following completion of delay calibration (using single-band
solutions ONLY) and bandpass calibration, POSSM displays show the data
is well calibrated (flat phs vs freq in ea. band with good alignment
among bands).

When multi-band solutions are used in the second FRING run of the delay
calibration, the end result is different. Individual bands show phase
slopes vs freq. and the alignment among IFs is worse.  To invoke
multi-band solutions, we use APARM(5)=2 in FRING.

Replication:  You can use the subset of data on anon-ftp to
replicate the problem.  SN5 contains the results of the single-band
solution.  CL8 implementats this solution via CLCAL.
To run FRING to obtain a multiband solution for comparison, use
APARM(5)=2 and GAINUSE=7.




Lincoln J. Greenhill      Harvard-Smithsonian Center for Astrophysics 
Radio & Geoastronomy Division, 60 Garden St, Cambridge, MA 02138, USA
Telephone:  1 617-495-7194             FAX:  1 617-495-7345
Internet:  greenhill at cfa.harvard.edu   http://cfa-www.harvard.edu/~lincoln