[evlatests] Stellar Results from K, Ka, and Q band antenna tests

[Rick Perley]

    Bob Hayward and I journeyed to Antenna 24 last Thursday to complete 
our extensive testing of the high frequency receivers.  We completed the 
standard suite of hot load, cold load, sky dips and rasters on Venus at 
15 frequencies, 5 within each of the three bands.  That we were able to 
complete all this in 6.5 hours of on-antenna time is testimony to the 
excellent state of all the software and hardware involved. 

    I have quickly calibrated all the data, the results of which are 
presented below in tabular form.    A proper memo describing the 
methodology and presenting the final results will be done later, 
probably in February.   The conversion from the antenna temperature due 
to Venus to antenna efficiency requires a significant corrections for 
antenna beam dilution and atmospheric absorption, and has not yet been 
done.  I may be able to get a rough estimate by Monday.  However, a 
'guesstimate' done for 33 GHz indicates ~40%, as expected. 

    A more sophisticated and accurate analysis will be done for the memo. 

    In brief, the values presented are derived this way:

    a) Conversion of the power data to calibrated temperature units is 
done from hot and cold load measurements.
    b) Tr = receiver temperature comes from the cold load power - 77K.
    c) Tcal = noise diode temperature, determined from the increment in 
power on the cold load when cals are turned on
    d) T90 = system temperature at zenith, taken from the sky dip.
    e) T8 = system temperature at the 8 degrees elevations, taken from 
the sky dip.
    f) Tatm = atmospheric emission at zenith, taken from the difference 
between T90 and T30. 
    g) Tsp = 'spillover' temperature, is equal to T90 - Tr - Tatm - 2.7K. 
    h) TVenus = antenna temperature due to Venus, taken from a 5 X 5 
raster, using a beamwidth/4 spacing. 

    All the data are of outstanding quality.  The values of, and 
variations in atmospheric emission and spillover contributions with 
frequency are credible.   The cold-sky system temperatures (T90) are 
fabulous -- easily passing the project requirements. 

   
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