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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 |
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select the bandwidth (in MHz) of IF pair AC from the
dropdown menu |
| AC filter |
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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 |
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requested observing frequency in IF pair AC |
| BD bandwidth |
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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 |
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requested observing frequency in IF pair BD |
| Go |
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do the calculation |
Remarks:
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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)
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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
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