[evlatests] X-band subband ordering

[Rick Perley]

    A quick perusal of X-band data shows that the ordering of the 
subbands is reversed:

    The correct spectral features (and continuity of phase) are 
recovered if the subbands are ordered {4,3,2,1}, rather than their 
current ordering {1,2,3,4}.  Note that this is not the same as simply 
reversing the frequency axis.  It appears the frequency ordering within 
each subband is correct (and runs 'backward'). 

    Data quality looks good, but a closer inspection is needed.