[daip] DBCON => UVFIX

[Eric Greisen]

Hanno Spreeuw wrote:
> Hi,
> 
> I think I may know what the problem is. These two observations both had 
> a 333 MHz IF (with Stokes RR only) and a 323 MHz IF (with Stokes LL only).
> What I did for both observations is to merge LL and RR, using DBCON. 
> DBCON does not accept different Stokes values, so I manipulated the 
> header (using PUTHEAD), so I turned the "LL IF "of both observations 
> into a fake "RR IF".
> So the file you downloaded is actually the DBCON of two files that were 
> also made by DBCON.
> Sorry I didn't mention this before, I totally forgot, I did this quite 
> some time ago.
> I suspect the problem has to do with the LL frequencies that are not 
> accurately represented in the headers.
> This final dataset is of pretty good quality, but I guess I hacked it to 
> the extent that UVFIX cannot be expected to work properly any longer.

DBCON when concatenating 2 single-source data sets just writes the u,v,w 
without change since they are already in wavelengths at whatever 
frequency they were observed.  However, UVFIX needs to know the correct 
frequency to compute new baselines in wavelengths from antenna stations 
in meters.  This is the origin of the problem.  UVFIX should be run 
early in the process, not at this late date...

Eric Greisen