[evlatests] S-Band test results

[Rick Perley]

    We have completed an initial round of testing the prototype S-band 
feed, installed on antenna 28. 

    Basic (and preliminary) results:

    1) System temperature is very good across the entire band:  25K, 
plus or minus 1 or 2. 
    2) System efficiency is a little lower than expected -- 50 to 55%. 
    3) Spillover at low elevations is higher than at L and C bands -- as 
expected.  The system temperature doubles at an elevation of about 11 
degrees.  (The feed is mounted at the high point in the feed ring, so 
when the antenna is pointed low, the spillover around the subreflector 
on the down side will go straight to ground). 
    4) The beamwidth is 14.6 arcminutes at 3.0 GHz, and is perfectly 
round to 2%. 
    5) First sidelobe levels are at the expected values:  -13 to -14 dB 
in the vertical and horizontal planes, -15 dB in the X-planes. 

    There is a significant pointing error -- 4.2 arcminutes, almost 
entirely in elevation. 

    A much more accurate analysis will be done when a receiver is 
installed on antenna 24, the 'standard calibration antenna'.