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Tied Array
A tied array capability is available for the Long Baseline Array
observations (e.g., VLBI). The tied array uses 64MHz bandwidth data from
the sampler and effectively adds them together. In this observation
mode, the correlator is usually used only for monitoring the data but
not for the processing. The output from the sampler goes to the Long
Baseline Array Data Acquisition System (LBA_DAS), from where it is
sent to S2 Recorder terminal and/or correlator. Output bandwidths
range from 64 MHz down to 62.5kHz in factors of 2. Passbands of 16MHz
and below may be tuned in 1Hz steps.
The tied array adder is controlled by the process CATIE which is now
available within CAOBS.
You will need to setup the system that you desire (i.e. antennas
and polarisations) and adjust the reference levels to make the
statistics shown on the CATIE page
approximately equal to
34%.
CACAL has the option of continuously calibrating the phase to keep the
tied array phased up. This mode can only be used if you are observing a
calibrator (i.e., the source has calcode=C in the schedule file).
You will need to run CACAL in interactive mode to be presented with
this option.
Another feature of CACAL is the option to put in a 90° phase shift
between the X and Y channel, effectively converting the polarisations
from linear to circular. This option is also accessible only by
running CACAL interactively.
Next: Reference Pointing
Up: Observing Modes
Previous: Frequency Switching and Multi-Frequency
Contents
Index
Robin Wark
2006-10-24