[evlatests] ea09 Antenna Gain Pulsations

[Rick Perley]

     I reported yesterday on a rapid gain variation in ea09, seen in (at 
least) L, C, X, and Ku bands.

     From the ACU/OTF tests done today, these rapid gain variations are 
still present.

     Ken asks if these are antenna-based, or are found only on some 
baselines.  The answer is:

     *The rapid variations are seen equally on all baselines*

     I attach a new plot to illustrate the problem.  This plot is in 
power units.

     Key points:

     1) It's antenna based.
     2) It's in one IF channel only.  (At X-band, it's IF 'D').
     3) It has a *perfect* 0.5 second period.   Even after many minutes, 
the pattern seen in the attached plot remains.
     4) There are four power states, each stable.
     5) The Pk to Pk power variation is 20% -- about 1 dB.
     6) There is no phase effect whatever.

     Fortunately (I suppose), the fact that the period is so close to 
0.5 seconds explains why this has not been seen in the past -- nearly 
everybody uses a multiple of 1.0 second averaging.

     Any ideas out there?




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