[evlatests] Antenna 4 Ka-band results

[Rick Perley]

    Bob, Brigette, and I spent most of Friday on antenna 4.  Weather was 
clear, dry (DP ~ 15 F) hot (Temp ~ 85F), and calm. 

    Detailed results will be given later.  I did a relatively quick 
calibration of all the data.  The results are summarized below. 


Freq.         Tsys       Tr       Tat       Tspill          Tcal        
T(3C273)        Effic.
-------------------------------------------------------------------------------------------------------
26232        71.7       42        6.2      23.5           6.10          
2.32             52%
28024        49.4       20.5     5.4      23.5           7.55          
2.33             52
33144        55.1       22.1                                  5.17
33160        56.8       22.7                                  
5.15          1.89             42
37000        62.9       29.8     7.8      25.3           3.42          
1.70             38
38064        68.0       34.3     8.7      25.0           3.40         
39600        74.5       39        9.2      26.3           2.40          
???               ???
----------------------------------------------------------------------------------------------------------

    Explanations:

    Blanks mean that quantity was not determined in these observations.  
The Tat, Tspill, and effics. have been determined from earlier 
measurements, with results that fit the trends shown in the table.
    The Efficiency is based on a flux of 3C273 = 25 Jy.  Craig tells me 
the VLBA measurements give 28.5 Jy at 22 GHz, and 24.5 Jy at 43 GHz.  
The values above will be close to real ...
    The ??? in the table are a results of a very unstable measurement of 
3C273 power at 39.6 GHz.  A best value is 2.0 K, which leads to an 
improbable 45% efficiency. 
    The spillover contribution is too high (compared to K and Q bands) 
by at least 10K at all frequencies.  The slow rise in Tspill is 
certainly real, but is likely due to an increase in the 'real' spillover.