[evlatests] Antenna 17, phase switching, and L-Band

[Rob Long]

Antenna 17 has been re-sync'd and reset.  Let me know if you still see 
the pulsing.

Rob

Rick Perley wrote:
>     We ran another quick stress file, and arranged to have antenna 17's 
> phase switching turned off. 
> 
>     I analyzed the results from L-band.  I find:
> 
>     1) The 1.67 period pulsing is gone.  Antenna 17 behaves normally now 
> -- mostly.  The reported Tsys (as found in the AIPS database) is 400K.  
> This is nonsense, since the antenna sensitivity is close to normal.  The 
> raw amplitudes from this antenna are too high by a factor of about 3.  
> Could somebody check the parameters database to see if the values there 
> are silly?   
> 
>     2) Antenna 25, which yesterday had a sensitivity too low by a factor 
> of 10 or more, is now just fine. 
> 
>     3) Antenna 13 is still in a very sad shape, with antenna sensitivity 
> (essentially, G/T) low by a factor of more than 10.  The Tsys values are 
> normal, so the problem lies elsewhere. 
> 
>     4) Antenna 21, on IFs A and B (i.e., RCP) has low sensitivity by a 
> factor of about 2.5.  The cause is easily found -- Tsys is too high by 
> the same factor. 
> 
>     5) Antenna 16, on IF B has low sensitivity by a factor of two -- and 
> a correspondingly high Tsys.  Curiously, this is only seen on B, and not 
> on A.  Normally, Tsys problems affect both IFs from the same polarization. 
> 
>     6) Antenna 4 is still doing its major dropout thing.  This is 
> clearly related to Tsys fluctuations, which have the same fast (0.4 
> seconds) changes on all IFs.  These effects are very large. 
> 
>     All else looks quite good. 
> 
>     I suggest that until we find the reason the phase switching is 
> messing up antenna 17, we leave it turned off for that antenna.
> 
> 
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