Online Loser Tool

The VLA Loser tool allows the user to enter observing frequency and bandwidth, and returns //LO and //FI cards which, in a standard VLA observe file, will result in a scan with the requested observing frequency and bandwidth.

The reason for the tool's existence is that EVLA antennas now can observe at L-band frequencies between 1000 and 1200 MHz, and observe and JObserve will not return LO settings in those cases.

Those interested in observing in that frequency range are advised to use JObserve to create a complete, valid, observe file at an L-band frequency acceptable by JObserve. Then, for every scan, use a standard editor to replace the //LO and //FI cards in the output files by the online Loser output.

Individual online Loser input fields:

AC bandwidth			select the bandwidth (in MHz) of IF pair AC from the dropdown menu
AC filter			select the additional front-end filter for IF pair AC from the drop- down menu. This will usually be 50 MHz. Note that any other choice will increase the probability of not finding any valid //LO and //FI cards
AC frequency			requested observing frequency in IF pair AC
BD bandwidth			select the bandwidth (in MHz) of IF pair BD from the dropdown menu
BD filter			select the additional front-end filter for IF pair BD from the drop- down menu. This will usually be 50 MHz. Note that any other choice will increase the probability of not finding any valid //LO and //FI cards
BD frequency			requested observing frequency in IF pair BD
Go			do the calculation

Remarks:

• If a valid solution is found for one IF pair and not for the other, the non-valid solution can be recognized by a first LO of 99.9999 (and '9's in other fields)
• The VLA observe file has a strict format, and editing errors can easily lead to erroneous observe files. We therefore strongly suggest that any observe file thus created be sent to vlahelp@nrao.edu well ahead of observing