cbw commissioning

aug17

     The cband wide receiver was installed in the cband high slot on the rotary floor. The hole in the floor for cband high
was larger than normal (cband high was supposed to have 2 horns).  Because of this, the mounting wedge (for the 8deg tilt) for cband wide did not span the current hole in the floor. The solution was to place a platform (piece of aluminum with a hole in the center) over the floor hole, and then mount the wedge on top of this platform.

     For adjustments in za direction, there are slots where the platform is mounted to the floor, and slots in the wedge were it is mounted to the platform.

    We attempted to mount  and position the horn without doing a theodolite survey. The values used to compute the motions can be found in (optics: motions and angles).



What we've done and settings used:


date

What was done:
turret
position
model offsets
 asecs  GC
az
za
before cbw

old cb high 165.01 -34.20
-93.52
170809

start
tracked sources
manually
160.
-34.20 -93.52
end
162.0
-34.20 -145.37 **
(-141.72)
170811

calib scans on
B1117+146
B1328+254 (3C287)
Plots:
plots of calibration results (.ps) (.pdf)
Beam maps
162.0 -34.20 -145.37
170814

moved horn uphill .391 inches
162.0
-34.20 -145.37
170815
start
move horn downhill .628 inches from 170809 position. then did manual pointing checks
162.0
-34.20
-122.86
end
measured az,za offsets:(.0045,.003)deg updated model offsets.
162.0
-18.20
-112.06

calib scans on B1328+252 (3C287). no rain, platform in focus.
Compare sidelobe height 11aug,15aug
Plots:
the standard calibration outputs  (.ps) (.pdf)
the sidelobe height for each  pattern (.ps) (.pdf)
sidelobe height at different horn positions (.ps) (.pdf)
Beam maps

162.0
-18.20
-112.06
170825

moved feed downhill 2 inches from 170815 final position
these are computed model offsets.
162
-18.20
-18.48
170829

manually updated model offsets
calib scans B1328+254, B1607+268 but missing td tension.
162
-27.20
-27.48








170809: manually tracked sources.


170811- calibration scans, first try. (top)

    Used 15:00 to 16:30 to run some calibration scans on cbw.
 The conditions were far from ideal for pointing,calibration tests (rain, no tiedowns).

The horn was sitting at the initial position (when first installed).

plots of calibration results (.ps) (.pdf)

cbw
cb
sefd
6Jy
3.8Jy
bmwidth
67asecs
62 asecs
coma
.14
.05
1st sidelobe(avg)
-13db
-15db


Beam maps:

    Beam maps were reconstructed from each calibration scan  for B1328+254.

freq
az,za range
(-120,14.7) -> (-127,11.6)
az,za range
(-130.9,10.7) -> (-146,8.2)
4500
 maps 1-4
maps 5-8
4860
maps 1-4 maps 5-8
5000
maps 1-4 maps 5-8
5385
maps 1-4 maps 5-8

processing: x101/170811/x102cbw.pro


170814: move horn .391 inches in za direction. (top)

    Felix moved the horn .391 inches in the za direction (toward the secondary..uphill). Manual pointing checks were then done to find the new pointing offsets. This move was in the wrong direction (i had gotten my signs backwards..). But it let us check the plate scale in the za direction... except that it was raining and the platform was not in focus...

processing: x101/170814/xbwtest.pro

170815: move horn downhill, then calib scans (top)

calibs scans on B1328+254 (3C287).

Plots made from the calibration scans:

The first set of plots shows the standard calibration outputs (gain,tsys,sefd,etc..) (.ps) (.pdf)
The 2nd set of  plots show the sidelobe height for each  pattern (.ps) (.pdf)

    The calibration measurement uses a spider scan:
    The total power from the 6 patterns is over plotted.

The 3rd set of plots  compare the  sidelobe height at different horn positions (.ps) (.pdf)

Beam maps:

   Beam maps were reconstructed from each of the 6 calibration scans  for B1328+254.

freq
az,za range
(-137,9.13) -> (-157,7.31)
az,za range
(-167.7,6.93) -> (-176,6.74)
4500
 maps 1-4
maps 5-6
4860
maps 1-4 maps 5-6
5000
maps 1-4 maps 5-6
5385
maps 1-4 maps 5-6

    You can clearly see the coma lobe at negative za.

Summary:

processing: x101/170815/x102cbw.pro


170829: beam maps after horn moved 2 inches.

    The horn was moved 2 inches downhill (from its original position) on 25aug17.
What was done on 29aug17:

   

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