[evlatests] 3bit-8bit Bandpass Stability

[Rick Perley]

    In reviewing the latest (and long) observation of 3 and 8 bit paths, 
it is again clear that the bandpass stability is essentially the same 
for all three paths -- and even follows the same patterns.  For all 
three, the temporal variations (indeed, larger than we would like) 
change smoothly over time. 

    To illustrate, review the attached 3 postscript plots.  They show 
the *differential* bandpass amplitudes, on a -1.5 to 1.5% scale.  The 
color coding is to help the eye.  Time moves upwards.  The left panel is 
RCP, the right panel is LCP.  A spectrum is plotted every 16 minutes.  
The three plots are for the same frequency, at the same time.  The 
source is 3C84.  This run was taken during a large temperature and 
elevation change. 

    I have yet to determine whether a simple interpolation over time 
will allow us to reach the demanding (.01%) goal.  But we might get 
close ...

    Certainly, the 8-bit side is no more variable or erratic than the 
3-bit.  The origin of these variations is elsewhere. 

   
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