[daip] New Ticket - [!SOR-264733]: UVPRT seems to get channel frequency wrong

[Michael Bietenholz]

New Ticket: UVPRT seems to get channel frequency wrong

UVPRT seems to get the channel frequency wrong, at least some of the time

I have a data set, header says this (channels are 2 MHz apart)

AIPS 1: Type    Pixels   Coord value     at Pixel     Coord incr   Rotat
AIPS 1: COMPLEX      3   1.0000000E+00       1.00  1.0000000E+00    0.00
AIPS 1: STOKES       4  -1.0000000E+00       1.00 -1.0000000E+00    0.00
AIPS 1: FREQ        32   1.0265000E+09      17.00  2.0000000E+06    0.00

UVPRT with BIF=1; CHANNEL=17 says:

File = 20121004 L  .UVCOP .   2   Vol = 1    Userid = 1777     Channel =   17     IF =  1
Chan freq=  1.058499970 GHz  Ncor=  4  No. vis=         2  Sort order= TB

And now with BIF=1; CHANNEL=18:

File = 20121004 L  .UVCOP .   2   Vol = 1    Userid = 1777     Channel =   18     IF =  1
Chan freq=  1.062499970 GHz  Ncor=  4  No. vis=         2  Sort order= TB

The two "Chan freq"s are 4 MHz apart, not the 2 MHz that the header suggests.
I tried this on two different data sets and saw the same thing.

The uvw values printed out seem to scale with frequency as calculated from header/FQ-table, rather than with the reported "Channel Frequency"




Ticket Details
===================
Ticket ID: SOR-264733
Department: AIPS Data Processing
Priority: Default
Status: Open
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=3325