[evlatests] P-band Status (13 Sept)

[Rick Perley]

    A number of changes have been made to the P-band system.  I took a 
quick look, and found:

     1)  All 27 antennas in the array fringed.   

    2)  Two antennas have polarizations reversed:  ea01 and ea17.  
However, the latter one is probably not a reversal.  See below under 
'polarization'. 

    3) Amplitudes are very low (by a factor of a few to a few tens) in:  
09$, 10R+L, 14R+L, 22R+L, 19L, 23L. 

    4) Amplitudes are very unsteady (but not weak) in ea12L.

    5) Amplitudes are changing smoothly (seen in amplitude and in 
switched power, by about 20% over 15 minutes) in  ea20L. 

    6) A strong 3.5 MHz ripple is seen in the bandpass of ea07R and 
ea25R.  (If a standing wave, the reflecting points are 43 meters apart! 
-- Hard to see how that happens). 

    7) I had thought ea01 was completely broken on one side -- but 
(after flipping the polarizations), I find that the antenna works as 
well as any of them! 

    8)  There was no switched power (meaning, just noise, with zero 
mean) in ea10, 11, 13, 17 19 and 25. 

    9) Cross polarization on nearly all antennas is much higher than I 
expect -- typically 10 to 20%.  I have trouble believing this is due to 
a dipole orientation issue, but continue to hope that it is.  The 
alternate explanations are all worse ... 

    10) ea17 is about 100% cross-polarized -- about equal power in all 
four correlations.  It would be useful to investigate this one first ...