TVCHAN settings affect your data

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TVCHAN settings affect your data

Postby baerbel » Mon Feb 08, 2010 1:42 pm

tvchan settings in CACOR / CABB define the channel range over which data is averaged and passed to CAOBS and VIS. Most importantly, the selected channel range is also used to generate the Tsys values in the RPFITS file headers.

Note: Different channel ranges are recommended for the 20cm and 13cm bands to provide an interference-free set of useful channels within the available band. Leaving tvchan unchanged when swapping from 20cm to 13cm will cause elevated Tsys values thereby affecting the data calibration, unless this is corrected using the miriad software. The same will occur when, e.g., swapping between 20cm and 6cm.

Thus, if tvchan is not set appropriately every time there is a frequency change that requires different channel ranges, the Tsys values will not be correct.

Mark Wieringa has implemented a new field in ATCAsched which can define a channel range. The parameters are four, comma separated, values representing (in order) the first and last tvchan for IF 1, and the first and last tvchan for IF 2. If it is left as blank (or null) then the correlator tvchan settings are kept, otherwise this field will override the correlator settings. These tvchan settings are settable for each scan.

See ATCA Current Issues at http://www.narrabri.atnf.csiro.au/observing/CurrentIssues.html (29 Jan 2010)
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Re: TVCHAN settings affect your data

Postby ste616 » Mon Feb 08, 2010 1:46 pm

Warwick is also trying to make the correlator software remember and restore tvchan ranges over configuration changes. Last I heard, there were still bugs in this feature, and Warwick is working on zoom modes. So for the moment, it is recommended that users take advantage of the scheduler field as Baerbel described. I will update when the correlator memory works.
cheers
Jamie Stevens
ATCA Senior System Scientist
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