.nf

If SWWOBBLER and ONOFF are combined in the standard way, we
effectively take data at 3 positions:

1. the source position
2. the source position + throw  (offset in the "true-angle" horizontal system)
3. the source position - throw  (offset in the "true-angle" horizontal system)

with throw = ABS(wOffset2-wOffset1).

Data from 1. are treated as source signal, data from 2 and 3 as
off-source reference signal.  Note that in the astronomical
coordinates, positions 2 and 3 will rotate around the source position
(1).  Therefore one must normally be sure that the extent of the source
is less than throw-beamWidth (/2).
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