MIT lincoln lab kildall wideband
13may14: one pol
1/2 the strength of the other (az strips at different turret
14may14: x102 calibration runs
16may14: rfi measurements with spectrum
lincoln lab returned with a wideband (400 to 3ghz) feed built
by per simon kildall.
It was installed 13may14. testing occurred 13may14 -> 16may14.
- Their system setup:
- the feed is dual pol
- each pol has two outputs that each go to a cooled
(70k) amplifier and then a hybrid combiner.
- the output of the combiner that goes to a power splitter. 1
signal continues to their system, the 2nd output goes to the
- The ttl cal pulse from downstairs is fed the 1pps tick. this
goes through the cbh cal pulse line to their system for
the start tick.
- ao signal
- there is a filter for each polarization
- polA 120 Mhz centered at 1420
- polB 250 Mhz centered at 1325
- the signal then goes to amp, pad, amp and then to the
cband high cable input in the blue rack
- We used cbh (or sbh?) cables and plugged then into
lbn port 6 (should have left them into cbh.. would have
saved some time).
- For pointing we used rcvNum 6 called test. the pointing
model was modelTEST.
- The experiment number was S2841
- ended up using 162.1 for turret position
- Info can be found under:
- /share/obs4/usr/s2841 . the ephemerides used
- During the run there was problem with one pol. The there was a
bad connection where the two log periodics of 1 pol exited at
the bottom of the feed.
- 12may14: start
installation of feed
- finish installation of feed.
- use az,za offset and scope to find rough estimate of
- calib scans. before changes do pointing model
- B0518+165 with fwhm beam =12amin..2 patterns
- B0518+165 with fwhm beam=4 amin. 5 patterns
- az strips through source at various
- B0758+143 (2.6Jy) 3 cycles of 9 strips
- B1005+077 (6.8Jy) 11 strips
- Showed that polB src deflection was 1/2 of polA when
measured in Tsys units.
- x102 calibration run midnite to 7:30
- file: corfile.14may14.x102.1
- used this to compute the pointing model offsets. only used
PolA, since polB was flakey.
- za offset: -5.53, az offset: -4.12. subtracted from
modelTEST pnt model file around 9:00 am.
- tried repairing polB by soldering bad feed connection.
- removed feed, soldered, then reinstalled.
- did calib run. PolB is not twice as large as polA source.
- didn't fix the problem
- Looks like they reversed the cables when plugging them
back into the feed.
- 13:00. calibration run on B1034+329
- 3 patterns,. showed that they had reversed the pol Cables
when reinstalling the feed.
- file: corfile.14may14.x102.2
- 13:50: az swing 270 to 630 and back za=18.
- 15:09: started tracking gps satellite
- adjusting power levels, putting in pads
- file: corfile.14may14.x101.2 scans 492,493
- track offset postions on gps satellite
- az,za Offset=.03333 Deg= 2 Arcminutes(great circle)
- 15:25:18 +az offset
- 15:26:18 -az offset
- 15:27:44 + za offset
- 15:28:30 -za offset
- 15:29:33 back on source
- 15:31:28 1.333 deg off source in az direction
- file: corfile.14may14.x101.2 scan 494.
- moved to 2nd gps satellite, calib 3 calib scans
- file corfile.14may14.x101.2 scans 413400495 to 413400512
- track their satellite (illuminated by radars)
- file: corfile14may14.x101.2
- scan 413400513 for 286 secs. then stopped to update
corfile config (256-> 1024 channels, lagc 10->9) t
- scan 413400513 till end
- we tracked the sat through these cor config
- tried repairing the
bad pol of the feed before afternoon run
- used sky, absorber to see if the fix worked: Morning
- file corfile.15may14.x101.1
- scan 387. on sky (39613 SecMidnite ast)
- scan 388 on absorber (39803 secMidnite ast)
- scan 389 on sky (40056 secMidnite ast)
- scan 390 on absorber (40202 secMidnite ast)
- calib scan on B0518+165 (4 patterns)
- Tracked their satellite till end of period
- file: corfile.15may14.x101.3
- brought feed down to lab. tried to resolder the bad pol
- reinstalled feed. polA still bad
- calib scans using different beam widths
- file corfile.16may14.x101.1
- 1405 3.7Amin they cycled dewar during this pattern.
- 1405 3.7 amin scan 251
- 1227 4.5 amin scan 257
- 1010 5.3 amin scan263
- 420 13.0 amin scan 270
- They tracked their satellite for the rest of the day.
- anritus spectrum analyzer installed in dome on polB
- rfi sweep while
- .cover 300 to 2000 Mhz
- start: linclab_rfiswp1_000.dat 15:20 ast
- end: linclab_rfiswp1_196.dat 16:14 ast
- cover 300 to 3100 Mhz
- start:linclab_rfiswp2_000.dat 16:15 ast
- end:linclab_rfiswp2_364.dat 17:55 ast
13may14 One pol is 1/2 the strength of the
Azimuth strips were done through a
source at different turret position (to see what the sidelobes
The plots show the total power vs
time for each strip (at different turret positions) (.ps) (.pdf)
- there were 9 strips done in a cycle. each strip differed from
the previous by (.5,.8) turret degrees (45 asecs on sky per
- 262.1 turret degrees was used as the center.
- B0758+143 (2.6Jy). .5 deg turret step between strips. 3
complete cycles done
- B1005+077 (6.8 Jy). .8 deg turret step between strips. 1
cycle plus 2 strips were done.
- Page 1: Src:B0758+143 (2.6 Jy)
- 3 cycles of 9 strips each were done
- The step size was .5 deg (turret). -2.0 to +2 turret degs
- black is polA, red is polB
- Each strips was normalized to +/- 12 points from the strip
- Top: PolA and polB power vs time for the 27 strips
- all the strips were plotted in sequence
- bottom: overplot the 27 strips
- the peak moves as the turret center used steps from -2. to
+2 turret degrees
- PolB is 1/2 of polA deflection
- Page 2: src B1005+077 (6.8 Jy)
- this used .8 deg turret steps (-3.2 to 3.2 turret degrees
- 1 cycle (9 strips) plus the first two of the 2nd cycle were
- The signal to noise for polB is 1/2 of the signal to noise for
- This could be because Tsys of polB is twice that of polA, or
that polB input is less sensitive.
- The sidelobes look more symmetric at an offset of -2 or -1.5
- Looking at other calibration runs, the sidelobes sometimes
looked symmetric when we were using 162.1 deg. The sidelobe
may also be a function of the az,za..
14may14 x102 calibration run (top)
An x102 calibration run was done 13may14 in
the afternoon and then again 14may14 in the early morning.
There is no cal for the linclab feed so the Tsys,gain measurements
are not valid. Polarization B was misbehaving so only polA
was used in the reduction.
The feed was worked on after the 13may14 run, so only the 14may14
early morning data is shown.
The plots show the calibration
results on the 3 sources (.pdf) (.pdf)
- Data was taken at 1405 Mhz. 14may14 00:00 to 7:30 am.
- Page 1: Gain,Tsys,SEFD, Beam width
- Only SEFD and Beam width are valid (no cal for the
- The SEFD is 13 to 15 Jy. (lband wide sefd is 2.5 to 3Jy)
- The fwhm beamwidth is 198 Asecs. lband wide fwhm at 1415 is
- the feed probably over illuminates the tertiary, giving a
- page 2: Coma,Sidelobe, efficiencies
- Only the sidelobe height is valid. It is about 15 db below
the peak. this is similar to lbw.
- page 2:Pointing error:
- za offset: -5, rms:4.1 asecs
- az offset: -4.8, rms 5.9 asecs
- +5, +4.78 asecs was added to the test model at 9:00 am
rfi measurements (top)
The anritsu spectrum analyzer was connected to
polB of the lincolnLab feed. It was used to monitor the rfi from
300 to 3000 Mhz.
The setup for the spectrum analyzer was:
The data format:
- 300Khz RBW, 165Mhz span, 551 channels. Average 30 sweeps in
trace 1, peak Hold in trace 2.
- It took about 15 seconds to acquire and record each 30 sweep
- Two sets of data were taken:
- 300 Mhz to 2000 Mhz. This took 10 steps to cover
- The telescope motion was:
- tracking quasar 3c138 for a few minutes
- move to az=370,65. so the guys could exit the dome
- Them move to start tracking the sat at for 16may14
- filenames:linclab_rfiswp1_000.dat -> 196.dat
- 300 Mhz to 3100 Mhz. This took 17 steps to cover.
- This was tracking the satellite the entire time.
- filenames:linclab_rfiswp2_000.dat -> 220dat
- 17:45 ast started moving to az=285,za=6.5
- ieee floating point data. little endian
- each 15 second acquisition was in a separate file
- the file contained:
- float dat[551,3]
- dat[*,0] is the frequency
- dat[*,1] is trace 1 (the average)
- dat[*,2] is trace 2 (the peak hold)