Compare kildal and german cortes horns

july 2003

     The horn on the lbw  receiver was switched from a kildal horn to one designed by german cortes in feb2003. On 11jul03 we did a test comparing tsys vs frequency for both horns. The correlator was setup to do 10 second cal onoff measurements in 100 Mhz junks covering 1120 to 1720 Mhz. For each measurement 3 complete passes were made through this frequency range. The radar blanker was enabled during the measurements. Blank sky was tracked with the za less than 12 degrees. The measurements started around 9:30 AST and finished at about 11:20 am. It took awhile for the techs to switch the horns. The sequence was: To select the blank sky I used NVSS and looked at 1 degree around the positions to see that there were no strong sources nearby. Unfortunately  the crab nebula is around 0534+220. After figuring this out i switched to a southern set of sources. I wasn't sure if the sidelobes were picking up different amounts of the crab. After switching to the southern source, the question was how much of the sun was in the sidelobes. The last measurement had the sun about 1 hour away in RA.

    An additional set of Tsys vs frequency measurements were done on 04jun03 with german's horn tracking blank sky at a declination of 18 deg. The za was less than 12 deg.

    The plots show the tsys vs frequency for the two feeds. Black is german's horn on 09jul03, blue is germans horn on 04jul03, and red is kildal's horn. Each frequency has 3 measurements spaced by about 4 minutes. The top plot is looking north and the bottom plot is looking south. The 18deg dec Tsys with german's horn taken on 04jun03 is over plotted in blue.

It looks like the measurements with germans horn at dec 14 are off. Probably because the sun was getting into the sidelobes.
The jumping around of the measurements is caused by some of the radars that were not blanked.
Germans horn looks to be about 1.5 Kelvins better than the kildal horn (at least the illumination pattern). There is not a strong frequency dependence.
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