[evlatests] Strange Tsys

[Peggy Perley]

I believe that feed heaters are either all on or all off at an antenna,
there isn't individual control for different feeds.  The op has
confirmed that the feed heaters were not 'on' last night at the
time of your tests.  What would be useful is an alert based on the
temp and dew point that advises the op to turn the feed heaters on, and
conversely, to turn them off (if on) under the appropriate conditions.

Peggy

Rick Perley wrote:
>     The best suggestion so far for the Tsys effect is dew on the feeds 
> -- a clear night, with the DP very close to the air temperature.    
> (This is confirmed by a look at the dewar temperatures -- which did not 
> change throughout). 
>     But we are supposed to have feed heaters to counteract this.  To 
> explain what we see, all VLA, and most EVLA heaters would have been off 
> during the run at both C and X bands.  But at K-band, it seems they were 
> on. 
> 
>     Can this -- and did this -- happen? 
> 
> 
> 
> 
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