[daip] Plotting in UVPLT in 31DEC12.

[Eric Greisen]

Nissim Kanekar wrote:
> 
> Dear Eric,
> 
> I've been trying to plot amplitude versus UV distance in UVPLT over a 
> specified UV range for some EVLA Q-band data (project 12B-408) using the 
> 31DEC12 version of AIPS. I find that when I use UVRANGE 1000-1200 (in 
> units of wavelength), the displayed plot covers the wavelength range 
> 890-1050 lambda. Also, the data plotted in VPLOT and UVPLT for the same 
> UVRANGE (and other) inputs are not the same. I didn't have this problem 
> with the 31DEC11 version of AIPS, so was wondering if it might be a new 
> bug.

UVRANGE is now a complicated subject.  The calibration application (data 
reading) routines apply the UVRANGE test.  That is applied to the U and 
V values at the reference channel in the reference (usually first) IF. 
After that UVPLT computes the correct UV distance for each channel that 
it plots.  When I worked with Crab Nebula data over 1 - 2 GHz I had to 
separate each "IF" into separate files so that UVRANGE in RFLAG would be 
something like meaningful.

Nothing has changed in this regard in a long time so I cannot understand 
how you have different results in 31DEC11 and 31DEC12.  The same data 
reading routines are used in VPLOT and UVPLT and the only test on 
UVRANGE is done in exactly the same way.

I just ran a test with uvrange = 2,3 and got 3.7 to 5.6 in IF 14.  I ran 
this in 31DEC13 and 31DEC11 and got the same UVPLT.

So I cannot find a problem other than a conceptual issue made worse by 
the wide passbands we now have.  To restrict UVRANGE control the X axis 
range and do not control UVRANGE in UVPLT.  I do not know what to do in 
VPLOT...

Eric Greisen