Compare kildal and german cortes horns
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.
Cortes horn tracking ra/dec: 5:10:00/22:20:00 start at 9:40 AST
Kildal horn tracking ra/dec: 5:50:00/22:20:00 start at 10:20 AST
Kildal horn tracking ra/dec: 6:00:00/14:12:30 start at 10:30 AST
Cortes horn tracking ra/dec: 6:40:00/14:12:30 start at 11:10 AST
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.
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.
Fig 1. POLA. tsys vs frequency.
Fig 2. POLB. tsys vs frequency.
Fig 3. TsysKildal - TsysGerman. The top plot is polA while the bottom plot
is polB. The crosses are looking north (dec 22) , the red * are looking
south (dec 14), and the blue + are Kildaldec14-germanDec18.
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.