[evlatests] EVLA antenna efficiency and sensitivity at X and Ku bands

[Rick Perley]

    Bob Hayward and I, ably assisted by Bob Stupak and Ravi 
Subrahmanyan, spend three days on ea24 in middle May to complete our 
calibrated load tests on that antenna.  A full report will be issued 
shortly with the results.  Here I give only the 'bottom line'. 
    Because of the uncertainty in the flux density of our normal 
absolute calibrator, Cygnus A, we used the planet Venus, which in 
mid-May was in the optimum  position for this work -- close to the 
earth, but still far enough from the sun to prevent sidelobe 
contamination of these total power tests. 

    A)  X-band:

    System temperatures at the zenith are all in the mid-20s K.  At 8 
degrees elevation, system temperatures rise to 41K.  Receiver 
temperatures are within 1 degree of 12K at all frequencies (spanning 
8.24 through 12.0 GHz).  These values are with 1K of those determined 
from our earlier data, taken last year. 
    Antenna efficiencies are close to 65% (as expected), with a slight 
decline between the lower and higher frequencies. 

    B)  Ku-band:

    Zenith system temperatures (determined from our earlier run, two 
years ago) are between the low 20s to mid 30s K (best in the middle of 
the band, rising at the edges).  Receiver temperatures are 6 to 15K, 
with the same dependency on frequency.  System temperatures at 8 degrees 
are higher by about 20 to 25K. 
    Antenna efficiencies are near 60%, declining slightly from low to 
high frequency. 

    Thanks to Bryan Butler for generating the model fluxes for Venus in 
a timely manner.