[evlatests] Observations of Switched Power

[Rick Perley]

    The 'Herc A' demo science run allows a perusal of the switched power 
at L, S, C, and X bands. 

    Overall, switched power does seem to be monitored and archived.  But 
perusing of so many data streams -- there are 4 bands x  2 polarizations 
x 16 subbands x 2 values = 256 data streams, all distressingly different 
-- leads to some difficulty in deducing global problems.  All of this is 
worsened by clear signs of RFI in many of the subbands ...

    Probably the most important deduction is the need for some 
automation in the judgement/smoothing of the switched power.  Although 
the AIPS task SNEDT is very handy in plotting/editing these data, it is 
not practical to do the essential operations individually for each of 
the 256 streams noted above ...  (and the problem will get much worse 
when we get 3-bit capability ...)

    The following is about all I can clearly see:

    1) L-band:  Antenna 9 still shows a PDif = 0 in LCP and <0 in RCP -- 
the data being essentially all noise on all subbands. 

    2) S-band:  Antenna 6 in RCP only has PDif values covering a much 
too large a range (about 50%), not normally distributed:  most values 
are at the high end, but with a significant fraction spread down to a 
level about half the maximum. 
    Also, in general, the PDif and PSum values show remarkable (and not 
right) behavior on nearly all subbands -- even those in which there 
appears to be no RFI and no disturbing influences.  I have not yet run 
SNPLT to review the spectra within these subbands. 

    3) There were two C-band tunings, one to cover the bottom half ( 4 
to 6 GHz), the other for the high half (6 to 8).  The problems noted 
here are common to both:
    a) antenna 12 shows Psum oscillating between two states, separated 
by ~5%, in IF 'B' only. 
    b) antenna 14 shows PDif = 0 (noise centered at zero) in LCP, all 
subbands.
    c) antenna 20 shows negative PDif for subbands numbered 11 and 
higher (IFs B and D) -- for all B/D IFs the values are not normal.  IFs 
A/C look fine. 
    d) Antenna 25 shows Psum and Pdif alternating between two states but 
by different factors (hence, Tsys is apparently also alternating, but 
the timescale for this is just not physically reasonable).    The ratio 
of the two states is about 1.12 and 1.05 for PSum and PDif, 
respectively.  This effect is seen on subbands 10 through 15 only!  (IFs 
B only). 

    4) X-Band:  All values looked fairly normal.  (But I'll confess that 
by the time I got to this, my eyes were losing focus, and my attention 
wandering ...)