Figure: The u-v plane coverage at 4.9 GHz for full synthesis of a
source at 
= 
with the VLA
in the B configuration.
Figure: The u-v plane coverage at 4.9 GHz for a full synthesis of a
source at = with the VLA
in the B configuration on the East and West arms, but in
the A configuration on the North arm (the BnA hybrid).
``Hybrid'' configurations occur during reconfigurations,
when the arms of the VLA may either be of different length, or have a
non-standard assortment of long and short baselines.
Hybrid configurations with long North arms are regularly
scheduled. They are useful when imaging regions
south of 
, where the north-south extent of
the u-v coverage of the standard configurations is seriously
foreshortened by projection. Figures 4 and
5 compare the u-v coverage
for the B configuration at = with
that of a hybrid configuration whose East and West arms are in
the B configuration but whose North arm is in the A
configuration. The baselines to the longer North arm fill in
a region around the v-axis that is left empty by the standard B
configuration. This BnA hybrid is available briefly
about every sixteen months, during a reconfiguration from A
to B. Similar CnB and DnC hybrids are
scheduled between the appropriate reconfigurations.