[evlatests] L-Band Performance at noon

[Rob Long]

Ant 18 IF-D had a bad T-5 causing issues with the Tsys values.  The SD 
voltage was consistently higher than the TP.  This T-5 has been swapped 
and seems to be working fine now.

Rob

Rick Perley wrote:
>     During Ken's lunch hour, I ran L-band to check on system 
> performance, and confirm the claimed sensitivity loss with cold-sky 
> observations. 
>     Six frequencies, spanning L-band from 1275 through 1706 MHz, were 
> chosen. 
> 
>     All four L-band-equipped EVLA antennas (13, 14, 16 and 18) are 
> performing magnificently.  There are no dropouts (seen with 3.3 second 
> averging) visible on any antenna, IF, or frequency.  None of the sudden 
> phase changes reported by Michael Rupen on 13 were seen.  The phase on 
> EVLA baseline 13-18 continues across frequency changes. 
>    
>     Items of concern:
> 
>     Antenna 14, IFs C and D, gave very weak fringes at 1670 and 1706 MHz 
> (respectively). 
> 
>     Antenna 18, IF D, is returning Tsys values that do not reflect 
> reality.  (The other IFs are fine).  
> 
>     All antennas show the now-familiar pattern of loss of sensitivity 
> with increasing frequency, as judged by AIPS weights.  
> 
>     Unfortunately, a blunder on my part resulted in no useful 'cold sky' 
> data from which to directly determine the system sensitivity.  I'll try 
> recover these observations later today. 
> 
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