[evlatests] Strange Tsys

[Rob Long]

Did the changes occur as the sun was coming up or with outside temp changes?

Rob

Peggy Perley wrote:
> 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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> 
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