[evlatests] L-band Problems

[Rick Perley]

     A short holography test yesterday gave the opportunity to check on 
L-band performance.  A few issues were noted:

     1) ea19 gave no signal (was 'dead') in LCP.    RCP was normal.

     2) ea18, in IF 'C', has an extraordinary bandpass!  The spectral 
power density in the central sections was near normal, but the bandpass 
slopes downwards smoothly towards both edges, with spectral power too 
low by about 20 dB at the extreme ends.  The phase structure is normal.  
I've attached a plot to demonstrate, showing the (normal) IF 'A' 
bandpass (upper) and the extraordinary IF 'C' bandpass (lower).  There 
are two traces for each, the upper is the phase, the lower the spectral 
power response.  I've never seen a parabola-like shape to the bandpass 
before ...

     3) ea24, in IF 'D', has low power and a fairly strong bandpass 
ripple (2 dB, pk-pk).  The ripple period is ~ 20 MHz, suggesting a 
reflection of length ~ 7.5 meters.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ea18BP.png
Type: image/png
Size: 71108 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/evlatests/attachments/20140416/ee98869a/attachment.png>